C A S S I N I MISSION PLAN. REVISION O, Change 1 August Jet Propulsion Laboratory California Institute of Technology

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1 C A S S I N I MISSION PLAN REVISION O, Change 1 August 2005 J Jet Propulsion Laboratory California Institute of Technology PD , Rev O, chg 1 JPL D-5564, Rev O, chg 1

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3 1.0 MISSION OVERVIEW Interplanetary Trajectory Tour Overview Reference Figures and Tables OPERATIONS OVERVIEW Ground Planning & Coordination Spacecraft Description Science Instruments The Huygens Probe System Tour Description & Strategies Telecommunications Playback DSN Lockup Maintenance Probe Relay Problem Data Routing and Storage Orbiter Telemetry Modes SSR Usage Data policing Carryover Navigation and maneuvers Tracking Maneuvers Main Engine usage Attitude Control S/C Attitude Definition Attitude Commanding Inertial Vector Propagation Turning the Spacecraft Target Motion Compensation Titan atmospheric model Minimum Flyby Altitudes Hydrazine usage Complications with Reaction Wheel Control Environmental hazards & control Radiation Thermal Control and Sun Exposure Dust Periodic Activities Engineering Maintenance Huygens Probe Checkouts Periodic Instrument Maintenance Contingency Plans When to halt the background sequence When to declare a spacecraft emergency High-Level Contingency Plans OPERATIONAL MODES, GUIDELINES AND CONSTRAINTS, AND CONTROLLED SCENARIO TIMELINES Operational Mode Definition Sequence Constructs Definition Requirements on the Design of Operational Modes Requirements on the Design of Modules Mission Design Guidelines & Constraints

4 3.5.1 Operational Modes and Sequence Constructs Sequence Development Spacecraft Pointing Telecommunications Management of On-Board Data Pre-Saturn Science Activities Saturn Tour & SOI Miscellaneous Controlled Scenario Timelines SELECTED REFERENCE PROJECT POLICY REQUIREMENTS (FROM 004) 5.0 MISSION PLANNING PROCEDURES

5 1.0 MISSION OVERVIEW The Cassini spacecraft is a combined Saturn orbiter and Titan atmospheric probe (to be delivered on the first or second flyby of Titan). It is a three-axis stabilized spacecraft equipped for 27 diverse science investigations with 12 orbiter and 6 Huygens probe instruments, one high gain and two low gain antennas, three Radioisotope Thermal Generators (RTGs) for power, main engines, attitude thrusters, and reaction wheels. Cassini was successfully launched on 15 October 1997 using the Titan IV/Centaur launch vehicle with Solid Rocket Motor Upgrade (SRMU) strap-ons and a Centaur upper stage. The spacecraft is flying a 6.7-year Venus-Venus-Earth-Jupiter Gravity Assist (VVEJGA) trajectory to Saturn, during which cruise science is planned to checkout, calibrate, and maintain the instruments as well as characterize the instruments and perform limited science observations. Cruise science is limited by flight software available on the spacecraft as well as cost, scheduling and workforce constraints. Limited science data collection occurred during the Venus flybys and science and calibration occurred during the Earth flyby. As the spacecraft approached Jupiter, science activities picked up as Jupiter observations served as preparation for the four-year tour of the Saturnian system. During most of the early portion of cruise, the High Gain Antenna (HGA) was required to shield most of the spacecraft from the Sun and only low-rate communications via the spacecraft s Low Gain Antennas (LGAs) was possible. Six months after the Earth flyby, the spacecraft was far enough from the Sun to orient the High Gain Antenna (HGA) to Earth enabling much faster communications. Following the Jupiter flyby, the spacecraft attempts to detect gravitational waves using its Ka-band and X-band radio equipment. Instrument calibrations, checkout, and other tour preparations are also conducted during the cruise between Jupiter and Saturn. In the six months preceding its arrival at Saturn, the spacecraft will conduct more intensive science activities, including observations of Phoebe immediately before arrival on 11 June During Saturn Orbit Insertion (SOI) on 1 July 2004, the spacecraft makes its closest approach to the planet s surface during the entire mission at an altitude of only 0.3 Saturn radii (18,000 km). Due to this unique opportunity, the approximately 100-minute SOI burn required to place Cassini in orbit around Saturn executes sooner than its optimal point centered around periapsis, and instead ends at periapsis, allowing science observations immediately after closest approach. At the third targeted Titan flyby, the ESA Huygens probe descends through the atmosphere of Titan to its surface. This probe is released from the orbiter 20 days before entry to Titan. Two days after probe release, the orbiter performs a deflection maneuver to place itself on the proper trajectory for the encounter. The probe flies directly into Titan's atmosphere, where it relays data to the orbiter for up to 2.5 hours during its descent to the surface. The orbiter then continues on a 74-orbit tour of the Saturnian system, including 45 close Titan flybys for gravity assist and science acquisition. The Titan flybys and Saturn orbits have been designed to maximize science coverage while meeting resource and operations limitations. Eight targeted and dozens of non-targeted flybys of selected icy satellites have also been included to determine icy satellite surface compositions and geologic histories. Cassini s orbital inclination varies widely to investigate the field, particle, and wave environment at high latitudes, including the hypothesized source of the unique Saturn kilometric radiation. High inclinations also permit high-latitude Saturn radio occultations, viewing of Saturn polar regions, and more nearly vertical viewing of Saturn's rings. The baseline mission ends in mid- 2008, for a total mission duration of 10.7 years. 1-1

6 PHASES O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M AM J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A Launch Initial Orbit Inner Cruise Outer Cruise Science Cruise Launch Sequence TCM1 HGA Venus 1 Venus 2 - Earth Transition ICO #2 Jupiter Quiet Cruise Space Science SUBPHASES ICO #1 Approach Science EVENTS Launch Venus1 Venus2 Earth Jupiter Science On Phoebe flyby SOI MANEUVERS PERIHELION/ APHELION CONJUNCTION OPPOSITION POINTING ANTENNA DOWNLINK DATA RATE CAPABILITY (Ranging ON) c bps (log scale) 248 k 142 k 82 k 35 k 22 k DSM SOI A P A P 1.02 AU 0.68 AU 1.58 AU 0.72 AU GWE Conj. Conj. opp GWE Experiment GWE Experiment GWE c c c c c c c Inf EARTH# Inf Sup Sup Sup Sup Sup SUN SUN EARTH EARTH EARTH/SCIENCE TARGET HGA# LGA LGA HGA HGA HGA high rates LGA HGA DSN COVERAGE REQUESTED (passes/week) DAYS FROM LAUNCH *Refer to Appendix J for more information about data rate capability. Superior Conjunction causes degradation of telemetry and radiometric tracking data. # Indicates actual instrument checkout window. Figure 1: Cassini Cruise Segment Timeline

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8 1.1 Interplanetary Trajectory Cassini's baseline trajectory is a VVEJGA (flybys of Venus twice, Earth and Jupiter) trajectory. This multiple gravity-assist trajectory is necessary because no existing launch vehicle/upper stage combination can place a spacecraft of Cassini's mass on a direct trajectory to Saturn. The minimum C 3 (or launch energy) required for a direct trajectory in 1997 is 108 km 2 /s 2. A JGA trajectory, with a single gravity-assist at Jupiter, would require a C 3 of 83 km 2 /s 2. The maximum C 3 achievable by the Titan IV (SRMU)/Centaur for the launch mass of Cassini was 34 km 2 /sec 2. This trajectory starts the spacecraft inward from the Earth s orbit, toward Venus, where the first Venus gravity assist places the spacecraft on a nearly resonant Venus-to-Venus transfer. A maneuver at aphelion of this loop lowers perihelion, allowing the trajectory to intersect Venus earlier, and with a greater flight path angle. The second flyby at Venus targets the spacecraft for a very quick transfer (approximately eight weeks) to Earth. This extremely fortuitous planetary phasing eliminates the need for an additional trajectory loop in the inner solar system. The spacecraft grazes Mars orbit on the Venus 1 - Venus 2 leg, and passes through the asteroid belt on the Earth - Jupiter leg of the trajectory. No asteroid flyby is included in the baseline due to a combination of ground system resource constraints and the high V cost to target to even the closest asteroid encounter. The Jupiter flyby imparts the remaining velocity required to reach Saturn, where arrival occurs on 1 July Figures 2.3 and 2.4 show the spacecraft interplanetary trajectory. 1.2 Tour Overview The reference tour consists of 74 orbits of Saturn with various orientations, orbital periods ranging from 7 to 118 days, and Saturn-centered periapsis radii ranging from about 2.7 to 15.6 R S (Saturn radii). Orbital inclination with respect to Saturn's equator ranges from ϒ, providing opportunities for ring imaging, magnetospheric coverage, and radio (Earth), solar, and stellar occultations of Saturn, Titan, and the ring system. A total of 45 targeted Titan flybys occur during the reference tour. Of these, 41 have flyby altitudes less than 2800 km and two have flyby altitudes greater than 10,000 km. Titan flybys are used to control the spacecraft's orbit about Saturn as well as for Titan science acquisition. The tour also contains 7 close flybys of icy satellites, and 30 additional distant flybys of icy satellites within 100,000 km. Close Titan flybys are capable of making large changes in the orbiter s trajectory. A single close flyby of Titan can change the orbiter s Saturn-relative velocity by more than 800 m/s. However, Titan is the only satellite of Saturn which is massive enough to use for orbit control during a tour. The masses of the others are so small that even close flybys (within several hundred km) only change the orbiter s trajectory slightly. Consequently, the Cassini tour consists mostly of Titan flybys. This places a restriction that each Titan flyby must place the orbiter on a trajectory leading back to Titan. The orbiter cannot be targeted to a flyby of a satellite other than Titan unless the flyby lies almost along a return path to Titan. The large number of Titan flybys does result in extensive coverage of Titan. Figure 2.5 shows a view from above Saturn's north pole of all tour orbits in a rotating coordinate system in which the Sun direction is fixed. This type of figure is often referred to as a "petal plot" due to the resemblance of the orbits to petals of a flower. The broad range of orbit orientations allows detailed survey of the magnetosphere and atmosphere of Saturn. Figure 1.6 shows a "side view", from a direction perpendicular to the plane formed by the Saturn-Sun line and Saturn s north pole, in which the inclination of the orbits is apparent. The tour is described in detail in the following subsections. 1.3 Reference Figures and Tables The following figures and tables provide reference data for the Cassini mission. Trajectory plots, encounters during the nominal tour and all events during the tour are given, as well as utility tables showing calendar date, one-way light time, weekday and day of year. 1-4

9 VENUS 1 SWINGBY 26 APR 1998 SATURN ARRIVAL 1 JUL 2004 VENUS 2 SWINGBY 24 JUN 1999 DEEP SPACE MANEUVER 3 DEC 1998 LAUNCH 15 OCT 1997 JUPITER FLYBY 30 DEC 2000 EARTH SWINGBY 18 AUG 1999 PERIHELIA 27 MAR AU 29 JUN AU Figure 3 CASSINI CRUISE TRAJECTORY

10 VENUS 2 FLYBY 24 JUN 1999 DEEP-SPACE MANEUVER DEC 1998 VENUS 1 FLYBY 26 APR 1998 EARTH FLYBY 18 AUG 1999 TICKS EVERY 30 DAYS TO JUPITER LAUNCH 15 OCT 1997 PERIHELIA 27 MAR AU 29 JUN AU Figure 4 Cassini Cruise Trajectory

11 Saturn Approach through Probe Mission 60.0 Range from Saturn (sunward), Rs SOI: 2004 Jul m/s, 96 min 0.0 Ta: 2004 Oct 1200 km Tb: 2004 Dec 2336 km Tc: 2005 Jan 60,000 km (Probe Descent) T0: 2004 Jul 339,000 km OTM-4: Ta-3d 2004 Oct 23 OTM-7: Tb-3d 2004 Dec 10 OTM-10A: ODM c/u 2005 Jan 04 Probe Release 2004 Dec 24 OTM-6: Apo 2004 Nov 21 OTM-10: ODM 2004 Dec m/s 2004 Jun 15 OTM-3: PRM c/u 2004 Sep OTM-5: Ta+3d 2004 Oct 29 OTM-8: PTM 2004 Dec m/s OTM-1: SOI c/u 2004 Jul 03 OTM-9: PTM c/u 2004 Dec 23 OTM1A: SOI c/u 2004 Jul Range from Saturn (along Saturn s direction of motion), Rs Time ticks every 2 days OTM-2: PRM 2004 Aug m/s Rev 0 Rev A Rev B Rev C Time ticks 2003 Jul 30

12 Figure 1.5 Tour Petal Plot-North Pole View (+X parallel to Saturn to Sun direction, +Z Saturn N. Pole) Figure 1.6 Tour Petal Plot - Side View 1-7

13 CASSINI CRUISE EVENT SUMMARY Name Epoch CAL DOW Comment Launch Oct15 Wed C3 = 16.6 km2/sec2 APHELION Nov06 Thu Sun range = 1.01 AU TCM Nov09 Sun V = 2.7 m/sec on ME o Conjunction Feb09 Mon Inferior conjunction TCM Feb25 Wed V = 0.2 m/sec on RCS PERIHELION Mar27 Fri Sun range = 0.67 AU (TCM-3) Apr08 Wed Canceled Venus flyby Apr26 Sun Altitude = 284 km; Speed = 11.8 km/sec (TCM-4) May14 Thu Canceled DSM Dec03 Thu V = 450 m/sec DSM Dec03 Thu V = m/sec on ME APHELION Dec07 Mon Sun range = 1.58 AU HGA Dec28 Mon 25 day checkout period o Opposition Jan09 Sat LGA Jan21 Thu Probe thermal constraints restrict HGA usage TCM Feb04 Thu V = 11.6 m/sec on ME TCM May18 Tue V = 0.2 m/sec on RCS (TCM-8) Jun03 Thu Canceled Venus flyby Jun24 Thu Altitude = 603 km; Speed = 13.6 km/sec PERIHELION Jun29 Tue Sun range = 0.72 AU TCM Jul06 Tue V = 43.5 m/sec on ME TCM Jul19 Mon V = 5.1 m/sec on ME TCM Aug02 Mon V = 36.3 m/sec on ME TCM Aug11 Wed V = 12.3 m/sec on ME o Conjunction Aug17 Tue Inferior conjunction Earth flyby Aug18 Wed Altitude = 1175 km; Speed = 19.0 km/sec TCM Aug31 Tue V = 6.7 m/sec on ME o Opposition Sep13 Mon Enter Asteroid Belt Dec11 Sat Sun range = 2.2 AU HGA Feb01 Tue HGA is Earth-pointed; use after this date Exit Asteroid Belt Apr12 Wed Sun range = 3.3 AU o Conjunction May13 Sat Superior Conjunction TCM Jun14 Wed V = 0.6 m/sec on ME TCM Sep14 Thu V = 0.2 m/sec on RCS o Opposition Nov28 Tue Gravity Wave Opportunity (TCM-16) Dec07 Thu Cancelled Jupiter flyby Dec30 Sat Altitude = 9,723,890 km; Speed = 11.6 km/sec TCM Feb28 Wed V = 1.0 m/sec on ME o Conjunction Jun07 Thu Superior Conjunction o Opposition Dec16 Sun Gravity Wave Experiment - opp±20 days TCM Apr03 Wed V = 1.2 m/sec on ME o Conjunction Jun21 Fri Conjunction Experiment - conj±15 days o Opposition Dec27 Fri Gravity Wave Experiment - opp±20 days TCM May01 Thu V = 1.6 m/sec on ME o Conjunction Jul01 Tue Conjunction Experiment - conj±15 days TCM-19A Sep10 Wed Test of tour RCS maneuver block TCM-19B Oct01 Wed Test of yaw steering, energy cutoff for SOI o Opposition Jan04 Sun Early Gravity Wave Experiment - Oct-Nov 2003 Start of tour May15 Sat Start of first tour sequence S1 TCM May27 Thu V = 34 m/sec on ME Phoebe flyby Jun11 Fri Altitude = 2000 km; Speed = 6.4 km/sec TCM Jun16 Wed V = 4 m/sec on ME TCM Jun21 Mon Emergency TCM window if needed SOI Jul01 Thu V = 626 m/sec EOM Jul05 Sat End of nominal tour sequences

14 CASSINI TOUR ENCOUNTERS All times are in SCET. For events with nonzero duration, epoch given is start. Seq Rev Name Event Epoch (SCET) Date DOW Comment S1 0 0PH (t) Phoebe T19:33 Jun11 Fri Was P1; inbound 1997 km flyby, v=6.4 km/s, Phase=25 deg S5 a ati (t) Titan T15:30 Oct26 Tue T N/A; inbound 1,200 km flyby, v=6.1 km/s, phase=91 deg S6 b bti (t) Titan T11:36 Dec13 Mon T N/A; inbound 2,336 km flyby, v=6.0 km/s, phase=98 deg S7 c cti (t) Titan T11:04 Jan14 Fri T N/A; inbound 60,000 km flyby, v=5.4 km/s, phase=93 deg S8 3 3TI (t) Titan T06:54 Feb15 Tue T3; inbound 950 km flyby, v=6.0 km/s, phase=102 deg S9 4 4EN (t) Enceladus T09:06 Mar09 Wed was E1; inbound 499 km flyby, v=6.6 km/s, phase=43 deg S9 5 5TI (t) Titan T19:55 Mar31 Thu T4; outbound 2,523 km flyby, v=5.9 km/s, phase=65 deg S10 6 6TI (t) Titan T19:05 Apr16 Sat T5; outbound 950 km flyby, v=6.1 km/s, phase=127 deg S EN (t) Enceladus T19:57 Jul14 Thu was E2; inbound 1000 km flyby, v=8.1 km/s, phase=43 deg S TI (t) Titan T08:40 Aug22 Mon T6; outbound 4,015 km flyby, v=5.8 km/s, phase=42 deg S TI (t) Titan T07:50 Sep07 Wed T7; outbound 950 km flyby, v=6.1 km/s, phase=84 deg S HY (t) Hyperion T01:41 Sep26 Mon was H1; outbound 990 km flyby, v=5.6 km/s, phase=45 deg S DI (t) Dione T17:58 Oct11 Tue was D1; inbound 500 km flyby, v=9.0 km/s, phase=66 deg S TI (t) Titan T03:58 Oct28 Fri T8; inbound 1,446 km flyby, v=5.9 km/s, phase=105 deg S RH (t) Rhea T22:35 Nov26 Sat was R1; inbound 500 km flyby, v=7.3 km/s, phase=87 deg S TI (t) Titan T18:54 Dec26 Mon T9; outbound 10,429 km flyby, v=5.6 km/s, phase=67 deg S TI (t) Titan T11:36 Jan15 Sun T10; inbound 2,042 km flyby, v=5.8 km/s, phase=121 deg S TI (t) Titan T08:20 Feb27 Mon T11; outbound 1,812 km flyby, v=5.9 km/s, phase=93 deg S TI (t) Titan T23:58 Mar18 Sat T12; inbound 1,947 km flyby, v=5.8 km/s, phase=148 deg S TI (t) Titan T20:53 Apr30 Sun T13; outbound 1,853 km flyby, v=5.8 km/s, phase=121 deg S TI (t) Titan T12:13 May20 Sat T14; inbound 1,879 km flyby, v=5.8 km/s, phase=163 deg S TI (t) Titan T09:12 Jul02 Sun T15; outbound 1,911 km flyby, v=5.8 km/s, phase=148 deg S TI (t) Titan T00:25 Jul22 Sat T16; inbound 950 km flyby, v=6.0 km/s, phase=105 deg S TI (t) Titan T20:12 Sep07 Thu T17; inbound 950 km flyby, v=6.0 km/s, phase=45 deg S TI (t) Titan T18:52 Sep23 Sat T18; inbound 950 km flyby, v=6.0 km/s, phase=90 deg S TI (t) Titan T17:23 Oct09 Mon T19; inbound 950 km flyby, v=6.0 km/s, phase=81 deg S TI (t) Titan T15:51 Oct25 Wed T20; inbound 950 km flyby, v=6.0 km/s, phase=25 deg S TI (t) Titan T11:35 Dec12 Tue T21; inbound 950 km flyby, v=6.0 km/s, phase=124 deg S TI (t) Titan T10:00 Dec28 Thu T22; inbound 1,500 km flyby, v=5.9 km/s, phase=62 deg S TI (t) Titan T08:34 Jan13 Sat T23; inbound 950 km flyby, v=6.0 km/s, phase=53 deg S TI (t) Titan T07:12 Jan29 Mon T24; inbound 2,776 km flyby, v=5.8 km/s, phase=73 deg S TI (t) Titan T03:10 Feb22 Thu T25; outbound 953 km flyby, v=6.3 km/s, phase=161 deg S TI (t) Titan T01:47 Mar10 Sat T26; outbound 956 km flyby, v=6.3 km/s, phase=149 deg S TI (t) Titan T00:21 Mar26 Mon T27; outbound 953 km flyby, v=6.3 km/s, phase=144 deg S TI (t) Titan T22:57 Apr10 Tue T28; outbound 951 km flyby, v=6.3 km/s, phase=137 deg S TI (t) Titan T21:32 Apr26 Thu T29; outbound 951 km flyby, v=6.3 km/s, phase=130 deg S TI (t) Titan T20:08 May12 Sat T30; outbound 950 km flyby, v=6.3 km/s, phase=121 deg S TI (t) Titan T18:51 May28 Mon T31; outbound 2,425 km flyby, v=6.1 km/s, phase=114 deg S TI (t) Titan T17:46 Jun13 Wed T32; outbound 950 km flyby, v=6.3 km/s, phase=107 deg S TI (t) Titan T17:05 Jun29 Fri T33; outbound 1,942 km flyby, v=6.2 km/s, phase=96 deg S TI (t) Titan T00:39 Jul19 Thu T34; inbound 1,302 km flyby, v=6.2 km/s, phase=34 deg S TI (t) Titan T06:34 Aug31 Fri T35; outbound 3,227 km flyby, v=6.1 km/s, phase=87 deg S IA (t) Iapetus T12:33 Sep10 Mon was I1; outbound 1000 km flyby, v=2.4 km/s, phase=65 deg S TI (t) Titan T04:48 Oct02 Tue T36; outbound 950 km flyby, v=6.3 km/s, phase=67 deg S TI (t) Titan T00:52 Nov19 Mon T37; outbound 950 km flyby, v=6.3 km/s, phase=51 deg S TI (t) Titan T00:06 Dec05 Wed T38; outbound 1,300 km flyby, v=6.3 km/s, phase=70 deg S TI (t) Titan T22:56 Dec20 Thu T39; outbound 953 km flyby, v=6.3 km/s, phase=61 deg S TI (t) Titan T21:26 Jan05 Sat T40; outbound 949 km flyby, v=6.3 km/s, phase=37 deg S TI (t) Titan T17:39 Feb22 Fri T41; outbound 959 km flyby, v=6.4 km/s, phase=30 deg S EN (t) Enceladus T19:05 Mar12 Wed was E3; inbound 995 km flyby, v=14.6 km/s, phase=56 deg S TI (t) Titan T14:35 Mar25 Tue T42; outbound 950 km flyby, v=6.4 km/s, phase=21 deg S TI (t) Titan T10:09 May12 Mon T43; outbound 950 km flyby, v=6.4 km/s, phase=35 deg S TI (t) Titan T08:33 May28 Wed T44; outbound 1,316 km flyby, v=6.3 km/s, phase=23 deg EM 78 78TI (t) Titan T02:20 Jul31 Thu T45; outbound 3,980 km flyby, v=6.1 km/s, phase=7 deg

15 CASSINI LOAD BOUNDARIES (APPROACH / TOUR)* Start End Length Name Date (SCET) CAL DOW Date (SCET) CAL DOW (days) C T12:25 Jan09 Fri T00:27 Feb20 Fri 42 C T00:27 Feb20 Fri T21:28 Apr01 Thu 42 C T21:28 Apr01 Thu T18:40 May14 Fri 43 S T18:40 May14 Fri T21:52 Jun19 Sat 36 S T21:52 Jun19 Sat T21:32 Jul30 Fri 41 S T21:32 Jul30 Fri T11:35 Sep12 Sun 44 S T11:35 Sep12 Sun T09:30 Oct18 Mon 36 S T09:30 Oct18 Mon T07:49 Nov15 Mon 28 S T07:49 Nov15 Mon T13:22 Dec16 Thu 31 S T13:22 Dec16 Thu T10:38 Jan22 Sat 37 S T10:38 Jan22 Sat T00:36 Feb27 Sun 36 S T00:36 Feb27 Sun T05:15 Apr09 Sat 41 S T05:15 Apr09 Sat T02:50 May14 Sat 35 S T02:50 May14 Sat T01:34 Jun18 Sat 35 S T01:34 Jun18 Sat T22:00 Jul31 Sun 44 S T22:00 Jul31 Sun T21:43 Aug30 Tue 30 S T21:43 Aug30 Tue T15:57 Oct08 Sat 39 S T15:57 Oct08 Sat T17:01 Nov12 Sat 35 S T17:01 Nov12 Sat T14:21 Dec17 Sat 35 S T14:21 Dec17 Sat T04:03 Jan27 Fri 41 S T04:03 Jan27 Fri T00:35 Mar11 Sat 43 S T00:35 Mar11 Sat T05:15 Apr22 Sat 42 S T05:15 Apr22 Sat T02:39 Jun03 Sat 42 S T02:39 Jun03 Sat T00:06 Jul17 Mon 44 S T00:06 Jul17 Mon T22:06 Aug19 Sat 34 S T22:06 Aug19 Sat T20:22 Sep20 Wed 32 S T20:22 Sep20 Wed T18:26 Oct22 Sun 32 S T18:26 Oct22 Sun T16:30 Nov24 Fri 33 S T16:30 Nov24 Fri T13:50 Jan05 Fri 42 S T13:50 Jan05 Fri T10:52 Feb17 Sat 43 S T10:52 Feb17 Sat T08:04 Mar28 Wed 39 S T08:04 Mar28 Wed T22:00 May04 Fri 38 S T22:00 May04 Fri T03:10 Jun11 Mon 37 S T03:10 Jun11 Mon T01:06 Jul14 Sat 33 S T01:06 Jul14 Sat T23:20 Aug11 Sat 29 S T23:20 Aug11 Sat T20:51 Sep22 Sat 42 S T20:51 Sep22 Sat T18:40 Oct31 Wed 39 S T18:40 Oct31 Wed T16:00 Dec14 Fri 44 S T16:00 Dec14 Fri T13:35 Jan22 Tue 39 S T13:35 Jan22 Tue T11:51 Feb16 Sat 25 S T11:51 Feb16 Sat T01:50 Mar23 Sun 36 S T01:50 Mar23 Sun T07:18 Apr19 Sat 27 S T07:18 Apr19 Sat T04:27 May31 Sat 42 S T04:27 May31 Sat T00:00 Jul05 Sat 35 *Note that S1 begins before the "official" start of the tour at SOI on July 1, 2004.

16 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S1 0 MAG Segment T18:40 May-14 Fri NA MAG segment begins. Duration = 27 d S1 0 S1 Begins T18:40 May-14 Fri NA S1 Sequence. Duration = 36 d S1 0 SOST Segment T04:02 Jun-11 Fri NA SOST segment begins. Duration = 2 d S1 0 00PH (t) [P1] PHOEBE T19:34 Jun-11 Fri NA Inbound 2071 km flyby, v = 6.4 km/s, phase = 24 deg S1 0 MAG Segment T22:32 Jun-12 Sat NA MAG segment begins. Duration = 18 d S2 0 S2 Begins T21:52 Jun-19 Sat NA S2 Sequence. Duration = 41 d S2 0 00PO (nt) POLYDEUCES T20:57 Jun-30 Wed NA Inbound km flyby, v = 13.3 km/s, phase = 90 deg S2 0 00CA (nt) CALYPSO T22:27 Jun-30 Wed NA Inbound km flyby, v = 14.1 km/s, phase = 92 deg S2 0 00ME (nt) METHONE T00:16 Jul-01 Thu NA Inbound km flyby, v = 12.9 km/s, phase = 96 deg S2 0 00MI (nt) MIMAS T00:30 Jul-01 Thu NA Inbound km flyby, v = 22.3 km/s, phase = 80 deg S _Rs Dust Hazard T00:44 Jul-01 Thu NA End 183T00:49(00:05) HGA to RAM S2 0 Ring CRX Ascending T00:46 Jul-01 Thu NA r = 2.63 Rs S2 0 SOI Start T01:12 Jul-01 Thu NA SOI burn start, DV= 626 m/s, duration = 01:36:20 (hh:mm:ss) S2 0 00PA (nt) PANDORA T01:16 Jul-01 Thu NA Inbound km flyby, v = 26.8 km/s, phase = 89 deg S2 0 00JA (nt) JANUS T01:51 Jul-01 Thu NA Inbound km flyby, v = 12.8 km/s, phase = 106 deg S2 0 Earth OCC RING T02:21 Jul-01 Thu NA Duration = 120 min; egress = T04:22 S2 0 Sun OCC RING T02:22 Jul-01 Thu NA Duration = 120 min; egress = T04:22 S2 0 Periapse T02:38 Jul-01 Thu NA Per = d, inc = 17.2 deg, r = 1.3 Rs, phase = 94 deg S2 0 SOI End T02:48 Jul-01 Thu NA SOI burn end S2 0 SOI Segment T03:07 Jul-01 Thu NA SOI segment begins. Duration = 1 d S2 0 Earth OCC SATURN T03:33 Jul-01 Thu NA Duration = 36 min; egress = T04:09 S2 0 Sun OCC SATURN T03:36 Jul-01 Thu NA Duration = 32 min; egress = T04:09 S2 0 00PM (nt) PROMETHEUS T03:57 Jul-01 Thu NA Outbound km flyby, v = 28.5 km/s, phase = 91 deg S2 0 00PN (nt) PAN T04:02 Jul-01 Thu NA Outbound km flyby, v = 22.8 km/s, phase = 88 deg S _Rs Dust Hazard T04:31 Jul-01 Thu NA End 183T04:36(00:05) HGA to RAM & MEA cover closed S2 0 Ring CRX Descending T04:34 Jul-01 Thu NA r = 2.63 Rs S2 0 TOST Segment T01:06 Jul-02 Fri NA TOST segment begins. Duration = 2 d S2 0 00TI (nt) TITAN T09:29 Jul-02 Fri NA Outbound km flyby, v = 8.3 km/s, phase = 67 deg S2 0 OTM-001 SOI c/u T14:06 Jul-03 Sat SOI cleanup (cancelled). D/L start, burn ~6h later. Backup D/L 186T14:06 S2 0 MAG Segment T01:19 Jul-04 Sun MAG segment begins. Duration = 34 d S2 0 SEP = 3.0 [deg] Conjunction T04:21 Jul-05 Mon Commanding must not be required below 3.0 deg S2 0 SEP = 2.0 [deg] Conjunction T10:13 Jul-06 Tue Plan no SSR playback below 2.0 deg S2 0 SEP = 1.0 [deg] Conjunction T16:28 Jul-07 Wed Require no DSN passes below 1.0 deg S2 0 SEP = 1.0 [deg] Conjunction T01:04 Jul-10 Sat Require no DSN passes below 1.0 deg S2 0 SEP = 2.0 [deg] Conjunction T07:12 Jul-11 Sun Plan no SSR playback below 2.0 deg S2 0 SEP = 3.0 [deg] Conjunction T12:52 Jul-12 Mon Commanding must not be required below 3.0 deg S2 0 OTM-001A SOI c/u T13:21 Jul-17 Sat SOI cleanup (cancelled). D/L start, burn ~6h later. Backup D/L 200T13:21 S3 0 S3 Begins T21:32 Jul-30 Fri S3 Sequence. Duration = 44 d S3 0 SATURN Segment T13:37 Aug-06 Fri SATURN segment begins. Duration = 80 d S3 0 OTM-002 PRM T09:53 Aug-23 Mon Periapsis raise DV= 393 m/s, duration = 00:50:53 (hh:mm:ss). D/L start, burn ~6h later. Backup D/L 237T09:38 S3 a Apoapse T08:57 Aug-27 Fri Per = d, inc = 17.6 deg, r = Rs, phase = 87 deg S3 a OTM-003 PRM c/u T10:30 Sep-07 Tue Periapsis raise clean up. D/L start, burn ~6h later. Backup D/L 252T10:25 S4 a S4 Begins T11:35 Sep-12 Sun S4 Sequence. Duration = 36 d S5 a S5 Begins T09:30 Oct-18 Mon S5 Sequence. Duration = 28 d S5 a OTM-004 ATI T00:16 Oct-23 Sat D/L start, burn ~6h later. Backup D/L 298T00:01 S5 a TOST Segment T16:31 Oct-25 Mon TOST segment begins. Duration = 2 d S5 a 0ATI (t) [TA] TITAN T15:30 Oct-26 Tue Inbound 1174 km flyby, v = 6.1 km/s, phase = 91 deg S5 a Ring CRX Ascending T16:53 Oct-26 Tue r = Rs S5 a RINGS Segment T09:16 Oct-27 Wed RINGS segment begins. Duration = 5 d S5 a Periapse T10:20 Oct-28 Thu Per = 47.9 d, inc = 13.8 deg, r = 6.2 Rs, phase = 104 deg S5 a Ring CRX Descending T20:01 Oct-28 Thu r = 8.08 Rs S5 a OTM-005 ATI T00:15 Oct-29 Fri D/L start, burn ~6h later. Backup D/L 304T00:30 S5 a MAG Segment T10:45 Nov-01 Mon MAG segment begins. Duration = 32 d S6 a S6 Begins T07:49 Nov-15 Mon S6 Sequence. Duration = 31 d S6 a OTM-006 APO T23:00 Nov-20 Sat D/L start, burn ~6h later. Backup D/L 326T23:00 S6 b Apoapse T08:41 Nov-21 Sun Per = 47.9 d, inc = 13.8 deg, r = 78.1 Rs, phase = 77 deg S6 b SATURN Segment T15:36 Dec-03 Fri SATURN segment begins. Duration = 7 d S6 b OTM-007 BTI T21:06 Dec-09 Thu D/L start, burn ~6h later. Backup D/L 345T21:05 S6 b TOST Segment T06:06 Dec-10 Fri TOST segment begins. Duration = 4 d S6 b 0BTI (t) [TB] TITAN T11:38 Dec-13 Mon Inbound 1192 km flyby, v = 6.1 km/s, phase = 102 deg S6 b Sun OCC TITAN T11:52 Dec-13 Mon Duration = 23 min; egress = T12:15 S6 b Ring CRX Ascending T14:57 Dec-13 Mon r = Rs S6 b SATURN Segment T07:52 Dec-14 Tue SATURN segment begins. Duration = 2 d S6 b 0BDI (nt) DIONE T01:41 Dec-15 Wed Inbound km flyby, v = 5.3 km/s, phase = 84 deg S6 b 0BMI (nt) MIMAS T05:02 Dec-15 Wed Inbound km flyby, v = 1.6 km/s, phase = 90 deg S6 b Periapse T05:51 Dec-15 Wed Per = 32.1 d, inc = 5.2 deg, r = 4.8 Rs, phase = 108 deg Page 1

17 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S6 b Ring CRX Descending T11:03 Dec-15 Wed r = 5.75 Rs S7 b MAG Segment T13:22 Dec-16 Thu MAG segment begins. Duration = 15 d S7 b S7 Begins T13:22 Dec-16 Thu S7 Sequence. Duration = 37 d S7 b OTM-008 PTM T19:22 Dec-16 Thu Probe targeting DV= 16 m/s. D/L start, burn ~6h later. Backup D/L 352T19:22 S7 b OTM-009 PTM c/u T18:52 Dec-22 Wed Probe targeting cleanup. D/L start, burn ~6h later. Backup D/L 358T18:52 S7 b Probe Release T02:00 Dec-25 Sat At entry interface d S7 b OTM-010 ODM T18:37 Dec-27 Mon Orbit deflection DV= 24 m/s. D/L start, burn ~6h later. Backup D/L 363T18:38 S7 b SOST Segment T01:30 Dec-31 Fri SOST segment begins. Duration = 2 d S7 c Apoapse T07:02 Dec-31 Fri Per = 31.9 d, inc = 5.3 deg, r = 59.7 Rs, phase = 72 deg S7 c 0CIA (nt) IAPETUS T18:49 Dec-31 Fri Inbound km flyby, v = 2.0 km/s, phase = 94 deg S7 c MAG Segment T04:38 Jan-02 Sun MAG segment begins. Duration = 13 d S7 c OTM-010A ODM c/u T17:38 Jan-03 Mon D/L start, burn ~6h later. Backup D/L 004T17:38 S7 c Probe Entry T09:06 Jan-14 Fri Entry interface alt=1270 km, Tc c/a -2.1 h S7 c 0CTI (t) [TC] TITAN T11:12 Jan-14 Fri Inbound km flyby, v = 5.4 km/s, phase = 93 deg S7 c Ring CRX Ascending T17:04 Jan-14 Fri r = Rs S7 c SOST Segment T12:00 Jan-15 Sat SOST segment begins. Duration = 3 d S7 c OTM-011 CTI T03:20 Jan-16 Sun D/L start, burn ~6h later. Backup D/L 017T03:30 S7 c 0CME (nt) METHONE T04:58 Jan-16 Sun Inbound km flyby, v = 1.8 km/s, phase = 78 deg S7 c 0CMI (nt) MIMAS T06:08 Jan-16 Sun Inbound km flyby, v = 1.3 km/s, phase = 100 deg S7 c Periapse T06:25 Jan-16 Sun Per = 33.5 d, inc = 5.2 deg, r = 4.8 Rs, phase = 106 deg S7 c 0CPL (nt) PALLENE T07:26 Jan-16 Sun Outbound km flyby, v = 2.4 km/s, phase = 138 deg S7 c Ring CRX Descending T11:58 Jan-16 Sun r = 5.90 Rs S7 c MAG Segment T10:00 Jan-18 Tue MAG segment begins. Duration = 17 d S8 c S8 Begins T10:38 Jan-22 Sat S8 Sequence. Duration = 36 d S8 c OTM-012 ~APO T01:08 Jan-28 Fri D/L start, burn ~6h later. Backup D/L 029T01:08 S8 3 Apoapse T03:26 Feb-01 Tue Per = 31.8 d, inc = 5.2 deg, r = 59.3 Rs, phase = 74 deg S8 3 SATURN Segment T11:07 Feb-04 Fri SATURN segment begins. Duration = 10 d S8 3 OTM-013 3TI T00:07 Feb-12 Sat D/L start, burn ~6h later. Backup D/L 043T16:37 S8 3 TOST Segment T09:07 Feb-14 Mon TOST segment begins. Duration = 2 d S8 3 03TI (t) [T3] TITAN T06:58 Feb-15 Tue Inbound 1579 km flyby, v = 6.0 km/s, phase = 99 deg S8 3 SOST Segment T09:00 Feb-16 Wed SOST segment begins. Duration = 2 d S8 3 Tethys Dust Crxing T20:04 Feb-16 Wed End 047T20:15(00:11) No protection yet identified S8 3 03PA (nt) PANDORA T23:03 Feb-16 Wed Inbound km flyby, v = 1.6 km/s, phase = 62 deg S8 3 E_ring_lg Dust Hazard T00:06 Feb-17 Thu End 048T00:18(00:12) MEA cover closed. HGA to RAM released. S8 3 03EP (nt) EPIMETHEUS T00:10 Feb-17 Thu Inbound km flyby, v = 2.9 km/s, phase = 78 deg S8 3 03AT (nt) ATLAS T00:23 Feb-17 Thu Inbound km flyby, v = 1.6 km/s, phase = 96 deg S8 3 03CA (nt) CALYPSO T00:35 Feb-17 Thu Inbound km flyby, v = 6.9 km/s, phase = 67 deg S8 3 Ring CRX Ascending T00:50 Feb-17 Thu r = 3.50 Rs S8 3 Periapse T00:57 Feb-17 Thu Per = 20.7 d, inc = 0.4 deg, r = 3.5 Rs, phase = 115 deg S8 3 03EN (nt) ENCELADUS T03:30 Feb-17 Thu Outbound 1264 km flyby, v = 6.7 km/s, phase = 113 deg S8 3 Earth OCC ENCELADUS T03:37 Feb-17 Thu Duration = 1 min; egress = T03:38 S8 3 Tethys Dust Crxing T05:40 Feb-17 Thu End 048T05:51(00:11) No protection yet identified S8 3 03PO (nt) POLYDEUCES T08:48 Feb-17 Thu Outbound 6441 km flyby, v = 8.6 km/s, phase = 121 deg S8 3 OTM-014 3TI T00:00 Feb-18 Fri D/L start, burn ~6h later. Backup D/L 049T23:36 S8 3 XDISC Segment T08:43 Feb-18 Fri XDISC segment begins. Duration = 18 d S8 3 Ring CRX Descending T04:44 Feb-26 Sat r = Rs S9 3 S9 Begins T00:36 Feb-27 Sun S9 Sequence. Duration = 41 d S9 4 Apoapse T06:20 Feb-27 Sun Per = 20.5 d, inc = 0.4 deg, r = 44.3 Rs, phase = 65 deg S9 4 OTM-015 ~APO T22:50 Mar-01 Tue D/L start, burn ~6h later. Backup D/L 061T22:50 S9 4 OTM-016 4EN T22:35 Mar-05 Sat D/L start, burn ~6h later. Backup D/L 065T22:20 S9 4 SOST Segment T07:34 Mar-08 Tue SOST segment begins. Duration = 2 d S9 4 04HE (nt) HELENE T04:33 Mar-09 Wed Inbound km flyby, v = 6.5 km/s, phase = 67 deg S _Rs Dust Crxing T06:46 Mar-09 Wed End 068T06:57(00:11) No protection yet identified S9 4 04EN (t) [E1] ENCELADUS T09:08 Mar-09 Wed Inbound 501 km flyby, v = 6.6 km/s, phase = 43 deg S9 4 E_ring_lg Dust Hazard T09:18 Mar-09 Wed End 068T11:02(01:43) HGA to RAM & MEA cover closed S9 4 Ring CRX Ascending T10:48 Mar-09 Wed r = 3.56 Rs S9 4 04AT (nt) ATLAS T11:29 Mar-09 Wed Inbound km flyby, v = 1.6 km/s, phase = 108 deg S9 4 Periapse T11:40 Mar-09 Wed Per = 20.8 d, inc = 0.2 deg, r = 3.5 Rs, phase = 115 deg S9 4 04TE (nt) TETHYS T11:44 Mar-09 Wed Outbound km flyby, v = 6.9 km/s, phase = 64 deg S9 4 E_ring_lg Dust Hazard T12:16 Mar-09 Wed End 068T12:18(00:01) MEA cover closed S9 4 Tethys Dust Crxing T16:22 Mar-09 Wed End 068T16:33(00:11) No protection yet identified S9 4 XDISC Segment T07:26 Mar-10 Thu XDISC segment begins. Duration = 18 d S9 4 OTM-017 4EN T21:20 Mar-11 Fri D/L start, burn ~6h later. Backup D/L 072T20:49 S9 4 Ring CRX Descending T17:01 Mar-14 Mon r = Rs S9 4 OTM-018 ~APO T12:19 Mar-19 Sat D/L start, burn ~6h later. Backup D/L 079T12:19 Page 2

18 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S9 5 Apoapse T17:35 Mar-19 Sat Per = 20.5 d, inc = 0.2 deg, r = 44.4 Rs, phase = 65 deg S9 5 OTM-019 5TI T20:00 Mar-27 Sun D/L start, burn ~6h later. Backup D/L 087T19:17 S9 5 MAG Segment T05:09 Mar-28 Mon MAG segment begins. Duration = 3 d S9 5 Mimas Dust Crxing T18:44 Mar-29 Tue End 088T18:55(00:11) No protection yet identified S9 5 05TE (nt) TETHYS T18:46 Mar-29 Tue Inbound km flyby, v = 12.2 km/s, phase = 124 deg S9 5 05EN (nt) ENCELADUS T20:32 Mar-29 Tue Inbound km flyby, v = 9.7 km/s, phase = 134 deg S9 5 05PL (nt) PALLENE T21:48 Mar-29 Tue Inbound km flyby, v = 7.0 km/s, phase = 137 deg S9 5 G_ring Dust Hazard T21:50 Mar-29 Tue End 088T22:58(01:07) MEA cover closed S9 5 05AT (nt) ATLAS T22:01 Mar-29 Tue Inbound km flyby, v = 1.3 km/s, phase = 68 deg S9 5 Ring CRX Ascending T22:59 Mar-29 Tue r = 3.53 Rs S9 5 05EP (nt) EPIMETHEUS T23:25 Mar-29 Tue Inbound km flyby, v = 2.3 km/s, phase = 102 deg S9 5 Periapse T23:38 Mar-29 Tue Per = 20.8 d, inc = 0.3 deg, r = 3.5 Rs, phase = 114 deg S9 5 05ME (nt) METHONE T00:50 Mar-30 Wed Outbound km flyby, v = 7.4 km/s, phase = 82 deg S9 5 05TL (nt) TELESTO T01:32 Mar-30 Wed Outbound km flyby, v = 6.5 km/s, phase = 61 deg S9 5 Mimas Dust Crxing T04:20 Mar-30 Wed End 089T04:32(00:11) No protection yet identified S9 5 05PO (nt) POLYDEUCES T05:59 Mar-30 Wed Outbound km flyby, v = 6.0 km/s, phase = 59 deg S9 5 TOST Segment T05:50 Mar-31 Thu TOST segment begins. Duration = 2 d S9 5 05TI (t) [T4] TITAN T20:05 Mar-31 Thu Outbound 2404 km flyby, v = 5.9 km/s, phase = 66 deg S9 5 Ring CRX Descending T22:06 Mar-31 Thu r = Rs S9 5 XDISC Segment T00:22 Apr-02 Sat XDISC segment begins. Duration = 10 d S9 5 OTM-020 5TI T20:22 Apr-03 Sun D/L start, burn ~6h later. Backup D/L 094T16:22 S9 6 Apoapse T23:32 Apr-06 Wed Per = 16.0 d, inc = 7.4 deg, r = 38.0 Rs, phase = 72 deg S10 6 S10 Begins T05:15 Apr-09 Sat S10 Sequence. Duration = 35 d S10 6 OTM-021 ~APO T20:00 Apr-09 Sat D/L start, burn ~6h later. Backup D/L 100T16:00 S10 6 RINGS Segment T06:30 Apr-12 Tue RINGS segment begins. Duration = 2 d S10 6 OTM-022 6TI T20:40 Apr-13 Wed D/L start, burn ~6h later. Backup D/L 105T02:14 S10 6 SATURN Segment T05:55 Apr-14 Thu SATURN segment begins. Duration = 2 d S PL (nt) PALLENE T20:31 Apr-14 Thu Inbound km flyby, v = 16.6 km/s, phase = 115 deg S ME (nt) METHONE T20:52 Apr-14 Thu Inbound km flyby, v = 12.3 km/s, phase = 118 deg S10 6 E_ring_lg Dust Hazard T22:12 Apr-14 Thu End 104T22:16(00:04) HGA to RAM & MEA cover closed S10 6 Tethys Dust Crxing T22:16 Apr-14 Thu End 104T22:20(00:04) No protection yet identified S10 6 Ring CRX Ascending T22:16 Apr-14 Thu r = 2.73 Rs S10 6 Periapse T23:16 Apr-14 Thu Per = 16.4 d, inc = 7.6 deg, r = 2.6 Rs, phase = 108 deg S10 6 Earth OCC RING T23:49 Apr-14 Thu Duration = 117 min; egress = T01:46 S10 6 Sun OCC RING T23:58 Apr-14 Thu Duration = 122 min; egress = T02:01 S EP (nt) EPIMETHEUS T00:14 Apr-15 Fri Outbound km flyby, v = 9.8 km/s, phase = 80 deg S MI (nt) MIMAS T01:25 Apr-15 Fri Outbound km flyby, v = 14.0 km/s, phase = 94 deg S CA (nt) CALYPSO T04:21 Apr-15 Fri Outbound km flyby, v = 12.5 km/s, phase = 115 deg S10 6 TOST Segment T06:25 Apr-16 Sat TOST segment begins. Duration = 2 d S TI (t) [T5] TITAN T19:12 Apr-16 Sat Outbound 1026 km flyby, v = 6.1 km/s, phase = 127 deg S10 6 Earth OCC TITAN T19:12 Apr-16 Sat Duration = 7 min; egress = T19:19 S10 6 Sun OCC TITAN T19:13 Apr-16 Sat Duration = 8 min; egress = T19:21 S10 6 Ring CRX Descending T19:58 Apr-16 Sat r = Rs S10 6 XDISC Segment T21:25 Apr-17 Sun XDISC segment begins. Duration = 12 d S10 6 OTM-023 6TI T18:59 Apr-19 Tue D/L start, burn ~6h later. Backup D/L 110T18:44 S10 7 Apoapse T23:30 Apr-23 Sat Per = 18.2 d, inc = 21.7 deg, r = 40.6 Rs, phase = 65 deg S10 7 OTM-024 ~APO T18:58 Apr-28 Thu D/L start, burn ~6h later. Backup D/L 119T18:28 S10 7 RINGS Segment T04:13 Apr-30 Sat RINGS segment begins. Duration = 5 d S HE (nt) HELENE T19:19 May-02 Mon Inbound km flyby, v = 9.9 km/s, phase = 107 deg S TE (nt) TETHYS T21:48 May-02 Mon Inbound km flyby, v = 9.3 km/s, phase = 110 deg S EP (nt) EPIMETHEUS T23:03 May-02 Mon Inbound km flyby, v = 6.2 km/s, phase = 46 deg S10 7 E_ring_lg Dust Hazard T23:35 May-02 Mon End 122T23:37(00:01) MEA cover closed S10 7 Ring CRX Ascending T23:36 May-02 Mon r = 3.90 Rs S10 7 Periapse T01:43 May-03 Tue Per = 18.4 d, inc = 21.9 deg, r = 3.6 Rs, phase = 115 deg S10 7 Earth OCC RING T02:56 May-03 Tue Duration = 343 min; egress = T08:39 S10 7 Sun OCC RING T03:24 May-03 Tue Duration = 361 min; egress = T09:25 S10 7 Earth OCC SATURN T04:40 May-03 Tue Duration = 144 min; egress = T07:03 S10 7 Sun OCC SATURN T05:11 May-03 Tue Duration = 153 min; egress = T07:44 S TL (nt) TELESTO T06:15 May-03 Tue Outbound km flyby, v = 8.3 km/s, phase = 98 deg S TI (nt) TITAN T05:37 May-04 Wed Outbound km flyby, v = 10.3 km/s, phase = 154 deg S10 7 SATURN Segment T20:30 May-04 Wed SATURN segment begins. Duration = 1 d S10 7 Ring CRX Descending T02:08 May-05 Thu r = Rs S10 7 XDISC Segment T03:40 May-06 Fri XDISC segment begins. Duration = 12 d S10 8 Apoapse T03:52 May-12 Thu Per = 18.2 d, inc = 21.9 deg, r = 40.6 Rs, phase = 65 deg S11 8 S11 Begins T02:50 May-14 Sat S11 Sequence. Duration = 35 d S11 8 RINGS Segment T03:00 May-18 Wed RINGS segment begins. Duration = 5 d Page 3

19 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S11 8 E_ring_lg Dust Hazard T03:53 May-21 Sat End 141T03:55(00:01) MEA cover closed S11 8 Ring CRX Ascending T03:54 May-21 Sat r = 3.90 Rs S11 8 Periapse T06:02 May-21 Sat Per = 18.4 d, inc = 21.9 deg, r = 3.6 Rs, phase = 114 deg S AT (nt) ATLAS T06:30 May-21 Sat Outbound km flyby, v = 6.7 km/s, phase = 145 deg S PM (nt) PROMETHEUS T06:47 May-21 Sat Outbound km flyby, v = 6.9 km/s, phase = 153 deg S11 8 Earth OCC RING T07:21 May-21 Sat Duration = 347 min; egress = T13:08 S11 8 Sun OCC RING T07:47 May-21 Sat Duration = 362 min; egress = T13:48 S EN (nt) ENCELADUS T08:13 May-21 Sat Outbound km flyby, v = 8.8 km/s, phase = 86 deg S11 8 Earth OCC SATURN T09:06 May-21 Sat Duration = 146 min; egress = T11:32 S11 8 Sun OCC SATURN T09:33 May-21 Sat Duration = 154 min; egress = T12:07 S11 8 SATURN Segment T19:00 May-22 Sun SATURN segment begins. Duration = 1 d S11 8 Ring CRX Descending T05:45 May-23 Mon r = Rs S11 8 XDISC Segment T02:42 May-24 Tue XDISC segment begins. Duration = 12 d S11 9 Apoapse T08:21 May-30 Mon Per = 18.2 d, inc = 21.9 deg, r = 40.6 Rs, phase = 66 deg S11 9 RINGS Segment T02:00 Jun-05 Sun RINGS segment begins. Duration = 5 d S TI (nt) TITAN T19:05 Jun-06 Mon Inbound km flyby, v = 5.8 km/s, phase = 83 deg S11 9 E_ring_lg Dust Hazard T08:25 Jun-08 Wed End 159T08:27(00:01) MEA cover closed S11 9 Ring CRX Ascending T08:26 Jun-08 Wed r = 3.91 Rs S PL (nt) PALLENE T09:58 Jun-08 Wed Inbound km flyby, v = 7.0 km/s, phase = 56 deg S CA (nt) CALYPSO T10:25 Jun-08 Wed Inbound km flyby, v = 7.8 km/s, phase = 64 deg S11 9 Periapse T10:37 Jun-08 Wed Per = 18.4 d, inc = 21.9 deg, r = 3.6 Rs, phase = 114 deg S11 9 Earth OCC RING T12:04 Jun-08 Wed Duration = 352 min; egress = T17:55 S11 9 Sun OCC RING T12:24 Jun-08 Wed Duration = 362 min; egress = T18:27 S11 9 Earth OCC SATURN T13:49 Jun-08 Wed Duration = 149 min; egress = T16:18 S11 9 Sun OCC SATURN T14:11 Jun-08 Wed Duration = 155 min; egress = T16:45 S11 9 SATURN Segment T17:21 Jun-09 Thu SATURN segment begins. Duration = 2 d S11 9 Ring CRX Descending T09:09 Jun-10 Fri r = Rs S11 9 XDISC Segment T01:25 Jun-12 Sun XDISC segment begins. Duration = 11 d S11 10 Apoapse T13:12 Jun-17 Fri Per = 18.2 d, inc = 21.8 deg, r = 40.7 Rs, phase = 66 deg S12 10 S12 Begins T01:34 Jun-18 Sat S12 Sequence. Duration = 44 d S TI (nt) TITAN T12:37 Jun-22 Wed Inbound km flyby, v = 3.7 km/s, phase = 65 deg S12 10 RINGS Segment T01:30 Jun-23 Thu RINGS segment begins. Duration = 5 d S TI (nt) TITAN T07:11 Jun-26 Sun Inbound km flyby, v = 7.7 km/s, phase = 111 deg S12 10 E_ring_lg Dust Hazard T13:29 Jun-26 Sun End 177T13:31(00:01) MEA cover closed S12 10 Ring CRX Ascending T13:30 Jun-26 Sun r = 3.93 Rs S PN (nt) PAN T14:23 Jun-26 Sun Inbound km flyby, v = 6.2 km/s, phase = 84 deg S TL (nt) TELESTO T14:50 Jun-26 Sun Inbound km flyby, v = 8.0 km/s, phase = 64 deg S12 10 Periapse T15:43 Jun-26 Sun Per = 18.4 d, inc = 21.8 deg, r = 3.6 Rs, phase = 113 deg S12 10 Earth OCC RING T17:21 Jun-26 Sun Duration = 358 min; egress = T23:19 S12 10 Sun OCC RING T17:35 Jun-26 Sun Duration = 364 min; egress = T23:39 S12 10 Earth OCC SATURN T19:07 Jun-26 Sun Duration = 152 min; egress = T21:39 S12 10 Sun OCC SATURN T19:21 Jun-26 Sun Duration = 156 min; egress = T21:57 S12 10 SATURN Segment T00:30 Jun-28 Tue SATURN segment begins. Duration = 1 d S12 10 Ring CRX Descending T13:45 Jun-28 Tue r = Rs S12 10 XDISC Segment T01:25 Jun-29 Wed XDISC segment begins. Duration = 13 d S12 11 Apoapse T18:58 Jul-05 Tue Per = 18.3 d, inc = 21.8 deg, r = 40.7 Rs, phase = 67 deg S12 11 OTM EN T14:37 Jul-08 Fri D/L start, burn ~6h later. Backup D/L 190T14:37 S12 11 SATURN Segment T23:30 Jul-11 Mon SATURN segment begins. Duration = 1 d S12 11 SOST Segment T23:30 Jul-12 Tue SOST segment begins. Duration = 3 d S PM (nt) PROMETHEUS T19:31 Jul-14 Thu Inbound km flyby, v = 6.1 km/s, phase = 51 deg S12 11 E_ring_lg Dust Hazard T19:55 Jul-14 Thu End 195T19:57(00:01) MEA cover closed S EN (t) [E2] ENCELADUS T19:55 Jul-14 Thu Inbound 172 km flyby, v = 8.2 km/s, phase = 64 deg S12 11 Ring CRX Ascending T19:56 Jul-14 Thu r = 3.95 Rs S ME (nt) METHONE T20:47 Jul-14 Thu Inbound km flyby, v = 7.6 km/s, phase = 110 deg S EP (nt) EPIMETHEUS T20:55 Jul-14 Thu Inbound km flyby, v = 6.3 km/s, phase = 84 deg S12 11 Periapse T22:10 Jul-14 Thu Per = 18.5 d, inc = 21.8 deg, r = 3.6 Rs, phase = 113 deg S12 11 Earth OCC RING T00:02 Jul-15 Fri Duration = 363 min; egress = T06:05 S12 11 Sun OCC RING T00:07 Jul-15 Fri Duration = 364 min; egress = T06:11 S12 11 Earth OCC SATURN T01:48 Jul-15 Fri Duration = 156 min; egress = T04:23 S12 11 Sun OCC SATURN T01:52 Jul-15 Fri Duration = 157 min; egress = T04:29 S12 11 SATURN Segment T23:30 Jul-15 Fri SATURN segment begins. Duration = 2 d S12 11 Ring CRX Descending T19:44 Jul-16 Sat r = Rs S12 11 XDISC Segment T23:20 Jul-17 Sun XDISC segment begins. Duration = 12 d S12 11 SEP = 3.0 [deg] Conjunction T04:31 Jul-20 Wed Commanding must not be required below 3.0 deg S12 11 SEP = 2.0 [deg] Conjunction T09:58 Jul-21 Thu Plan no SSR playback below 2.0 deg S12 11 SEP = 1.0 [deg] Conjunction T15:49 Jul-22 Fri Require no DSN passes below 1.0 deg Page 4

20 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S12 12 Apoapse T01:58 Jul-24 Sun Per = 18.3 d, inc = 21.8 deg, r = 40.8 Rs, phase = 67 deg S12 12 SEP = 1.0 [deg] Conjunction T23:08 Jul-24 Sun Require no DSN passes below 1.0 deg S12 12 SEP = 2.0 [deg] Conjunction T04:45 Jul-26 Tue Plan no SSR playback below 2.0 deg S12 12 SEP = 3.0 [deg] Conjunction T09:48 Jul-27 Wed Commanding must not be required below 3.0 deg S12 12 SATURN Segment T21:30 Jul-29 Fri SATURN segment begins. Duration = 2 d S13 12 SOST Segment T22:00 Jul-31 Sun SOST segment begins. Duration = 3 d S13 12 S13 Begins T22:00 Jul-31 Sun S13 Sequence. Duration = 30 d S13 12 E_ring_lg Dust Hazard T03:34 Aug-02 Tue End 214T03:36(00:01) MEA cover closed S13 12 Ring CRX Ascending T03:35 Aug-02 Tue r = 3.95 Rs S MI (nt) MIMAS T04:24 Aug-02 Tue Inbound km flyby, v = 6.1 km/s, phase = 57 deg S PM (nt) PROMETHEUS T05:17 Aug-02 Tue Inbound km flyby, v = 6.3 km/s, phase = 110 deg S13 12 Periapse T05:50 Aug-02 Tue Per = 18.5 d, inc = 21.8 deg, r = 3.6 Rs, phase = 112 deg S13 12 Sun OCC RING T07:50 Aug-02 Tue Duration = 365 min; egress = T13:55 S CA (nt) CALYPSO T07:54 Aug-02 Tue Outbound km flyby, v = 7.1 km/s, phase = 74 deg S13 12 Earth OCC RING T07:56 Aug-02 Tue Duration = 367 min; egress = T14:03 S13 12 Sun OCC SATURN T09:35 Aug-02 Tue Duration = 157 min; egress = T12:12 S13 12 Earth OCC SATURN T09:40 Aug-02 Tue Duration = 158 min; egress = T12:19 S TI (nt) TITAN T15:59 Aug-02 Tue Outbound km flyby, v = 6.5 km/s, phase = 34 deg S13 12 OTM-026 NEARP T05:50 Aug-03 Wed D/L start, burn ~6h later. Backup D/L 216T13:20 S13 12 SATURN Segment T14:50 Aug-03 Wed SATURN segment begins. Duration = 1 d S13 12 Ring CRX Descending T02:42 Aug-04 Thu r = Rs S13 12 XDISC Segment T22:20 Aug-04 Thu XDISC segment begins. Duration = 13 d S TI (nt) TITAN T12:32 Aug-06 Sat Outbound km flyby, v = 3.8 km/s, phase = 62 deg S13 12 OTM-027 ~APO T07:21 Aug-10 Wed D/L start, burn ~6h later. Backup D/L 223T12:52 S13 13 Apoapse T08:30 Aug-11 Thu Per = 18.2 d, inc = 21.9 deg, r = 40.7 Rs, phase = 68 deg S13 13 RINGS Segment T18:00 Aug-17 Wed RINGS segment begins. Duration = 4 d S13 13 OTM TI T05:00 Aug-18 Thu D/L start, burn ~6h later. Backup D/L 231T05:00 S TE (nt) TETHYS T07:02 Aug-20 Sat Inbound km flyby, v = 12.4 km/s, phase = 123 deg S13 13 Mimas Dust Hazard T08:59 Aug-20 Sat End 232T09:01(00:01) MEA cover closed S13 13 Ring CRX Ascending T09:00 Aug-20 Sat r = 3.93 Rs S13 13 Periapse T11:15 Aug-20 Sat Per = 18.4 d, inc = 21.9 deg, r = 3.6 Rs, phase = 112 deg S TL (nt) TELESTO T12:13 Aug-20 Sat Outbound km flyby, v = 7.8 km/s, phase = 67 deg S13 13 Sun OCC RING T13:18 Aug-20 Sat Duration = 365 min; egress = T19:22 S13 13 Earth OCC RING T13:37 Aug-20 Sat Duration = 368 min; egress = T19:45 S13 13 Sun OCC SATURN T15:01 Aug-20 Sat Duration = 158 min; egress = T17:39 S13 13 Earth OCC SATURN T15:17 Aug-20 Sat Duration = 161 min; egress = T17:58 S13 13 TOST Segment T21:20 Aug-21 Sun TOST segment begins. Duration = 2 d S13 13 Ring CRX Descending T07:31 Aug-22 Mon r = Rs S TI (t) [T6] TITAN T08:54 Aug-22 Mon Outbound 3669 km flyby, v = 5.9 km/s, phase = 44 deg S13 13 XDISC Segment T13:42 Aug-23 Tue XDISC segment begins. Duration = 10 d S13 13 OTM TI T11:08 Aug-25 Thu D/L start, burn ~6h later. Backup D/L 238T10:59 S13 14 Apoapse T12:03 Aug-28 Sun Per = 16.0 d, inc = 15.6 deg, r = 37.8 Rs, phase = 75 deg S13 14 OTM-030 ~APO T12:43 Aug-30 Tue D/L start, burn ~6h later. Backup D/L 243T10:38 S14 14 S14 Begins T21:43 Aug-30 Tue S14 Sequence. Duration = 39 d S14 14 RINGS Segment T20:00 Sep-02 Fri RINGS segment begins. Duration = 4 d S14 14 OTM TI T11:30 Sep-03 Sat D/L start, burn ~6h later. Backup D/L 247T10:30 S _Rs Dust Hazard T10:23 Sep-05 Mon End 248T10:24(00:00) MEA cover closed S14 14 E_ring_lg Dust Hazard T10:36 Sep-05 Mon End 248T10:41(00:04) MEA cover closed S14 14 Ring CRX Ascending T10:39 Sep-05 Mon r = 2.93 Rs S PA (nt) PANDORA T11:31 Sep-05 Mon Inbound km flyby, v = 7.0 km/s, phase = 57 deg S PM (nt) PROMETHEUS T11:32 Sep-05 Mon Inbound km flyby, v = 14.6 km/s, phase = 151 deg S14 14 Periapse T11:52 Sep-05 Mon Per = 16.3 d, inc = 16.0 deg, r = 2.7 Rs, phase = 105 deg S14 14 Sun OCC RING T12:38 Sep-05 Mon Duration = 316 min; egress = T17:54 S14 14 Earth OCC RING T12:51 Sep-05 Mon Duration = 331 min; egress = T18:22 S ME (nt) METHONE T13:57 Sep-05 Mon Outbound km flyby, v = 10.2 km/s, phase = 91 deg S14 14 Sun OCC SATURN T14:37 Sep-05 Mon Duration = 136 min; egress = T16:54 S14 14 Earth OCC SATURN T14:53 Sep-05 Mon Duration = 146 min; egress = T17:20 S14 14 TOST Segment T20:30 Sep-06 Tue TOST segment begins. Duration = 2 d S14 14 Ring CRX Descending T06:46 Sep-07 Wed r = Rs S TI (t) [T7] TITAN T08:12 Sep-07 Wed Outbound 1075 km flyby, v = 6.1 km/s, phase = 85 deg S14 14 XDISC Segment T12:46 Sep-08 Thu XDISC segment begins. Duration = 14 d S14 14 OTM TI T11:09 Sep-10 Sat D/L start, burn ~6h later. Backup D/L 254T09:30 S14 15 Apoapse T16:50 Sep-14 Wed Per = 18.4 d, inc = 0.3 deg, r = 41.5 Rs, phase = 74 deg S14 15 OTM-033 ~APO T10:40 Sep-19 Mon D/L start, burn ~6h later. Backup D/L 263T10:15 S14 15 SATURN Segment T18:43 Sep-22 Thu SATURN segment begins. Duration = 3 d S14 15 OTM HY T01:45 Sep-23 Fri D/L start, burn ~6h later. Backup D/L 267T10:20 S14 15 Tethys Dust Crxing T16:24 Sep-23 Fri End 266T16:34(00:09) No protection yet identified Page 5

21 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S14 15 Ring CRX Ascending T17:16 Sep-23 Fri r = 4.46 Rs S14 15 Dione Dust Hazard T17:28 Sep-23 Fri End 266T18:35(01:06) HGA to RAM & MEA cover closed S CA (nt) CALYPSO T18:51 Sep-23 Fri Inbound km flyby, v = 7.0 km/s, phase = 83 deg S MI (nt) MIMAS T19:39 Sep-23 Fri Inbound km flyby, v = 11.8 km/s, phase = 133 deg S14 15 Mimas Dust Crxing T20:24 Sep-23 Fri End 266T21:23(00:59) No protection yet identified S14 15 Periapse T21:36 Sep-23 Fri Per = 18.6 d, inc = 0.3 deg, r = 3.0 Rs, phase = 107 deg S14 15 Mimas Dust Crxing T21:48 Sep-23 Fri End 266T22:47(00:59) No protection yet identified S PM (nt) PROMETHEUS T22:26 Sep-23 Fri Outbound km flyby, v = 7.6 km/s, phase = 159 deg S14 15 Tethys Dust Crxing T02:38 Sep-24 Sat End 267T02:47(00:09) No protection yet identified S TE (nt) TETHYS T02:42 Sep-24 Sat Outbound 1500 km flyby, v = 9.0 km/s, phase = 68 deg S14 15 E_ring_lg Dust Hazard T05:05 Sep-24 Sat End 267T05:22(00:16) HGA to RAM & MEA cover closed S14 15 Ring CRX Descending T07:42 Sep-24 Sat r = 7.58 Rs S TI (nt) TITAN T22:47 Sep-24 Sat Outbound km flyby, v = 10.7 km/s, phase = 149 deg S14 15 SOST Segment T13:40 Sep-25 Sun SOST segment begins. Duration = 1 d S HY (t) [H1] HYPERION T02:25 Sep-26 Mon Outbound 514 km flyby, v = 5.6 km/s, phase = 47 deg S14 15 XDISC Segment T19:20 Sep-26 Mon XDISC segment begins. Duration = 14 d S14 15 OTM HY T10:11 Sep-28 Wed D/L start, burn ~6h later. Backup D/L 272T10:00 S14 15 OTM-036 ~APO T08:26 Oct-01 Sat D/L start, burn ~6h later. Backup D/L 275T11:00 S14 16 Apoapse T23:33 Oct-02 Sun Per = 18.2 d, inc = 0.3 deg, r = 41.2 Rs, phase = 74 deg S14 16 OTM DI T03:30 Oct-08 Sat D/L start, burn ~6h later. Backup D/L 282T09:12 S15 16 S15 Begins T12:30 Oct-08 Sat S15 Sequence. Duration = 35 d S15 16 SOST Segment T18:27 Oct-10 Mon SOST segment begins. Duration = 3 d S TI (nt) TITAN T22:22 Oct-10 Mon Inbound km flyby, v = 9.7 km/s, phase = 65 deg S DI (t) [D1] DIONE T17:52 Oct-11 Tue Inbound 500 km flyby, v = 9.1 km/s, phase = 66 deg S15 16 Tethys Dust Crxing T20:20 Oct-11 Tue End 284T20:29(00:09) No protection yet identified S TL (nt) TELESTO T20:26 Oct-11 Tue Inbound 9524 km flyby, v = 8.7 km/s, phase = 63 deg S15 16 Ring CRX Ascending T20:36 Oct-11 Tue r = 4.78 Rs S15 16 Dione Dust Hazard T21:24 Oct-11 Tue End 284T21:47(00:23) MEA cover closed. HGA to RAM released. S PL (nt) PALLENE T22:48 Oct-11 Tue Inbound km flyby, v = 10.8 km/s, phase = 125 deg S15 16 OTM DI T23:57 Oct-11 Tue D/L start, burn ~6h later. Backup D/L 286T10:40 S15 16 Tethys Dust Crxing T00:20 Oct-12 Wed End 285T01:25(01:04) No protection yet identified S15 16 Periapse T01:31 Oct-12 Wed Per = 18.7 d, inc = 0.4 deg, r = 3.0 Rs, phase = 106 deg S15 16 Tethys Dust Crxing T01:37 Oct-12 Wed End 285T02:42(01:04) No protection yet identified S AT (nt) ATLAS T01:54 Oct-12 Wed Outbound km flyby, v = 4.0 km/s, phase = 143 deg S EN (nt) ENCELADUS T03:03 Oct-12 Wed Outbound km flyby, v = 6.8 km/s, phase = 73 deg S15 16 Tethys Dust Crxing T06:33 Oct-12 Wed End 285T06:43(00:09) No protection yet identified S15 16 Dione Dust Hazard T09:01 Oct-12 Wed End 285T09:17(00:16) HGA to RAM & MEA cover closed S15 16 Ring CRX Descending T09:58 Oct-12 Wed r = 6.69 Rs S15 16 XDISC Segment T19:55 Oct-13 Thu XDISC segment begins. Duration = 14 d S15 17 Apoapse T00:00 Oct-20 Thu Per = 17.9 d, inc = 0.4 deg, r = 40.7 Rs, phase = 74 deg S15 17 OTM-039 ~APO T08:58 Oct-21 Fri D/L start, burn ~6h later. Backup D/L 286T10:40 S15 17 OTM TI T01:14 Oct-25 Tue D/L start, burn ~6h later. Backup D/L 295T01:29 S15 17 TOST Segment T18:29 Oct-27 Thu TOST segment begins. Duration = 2 d S TI (t) [T8] TITAN T04:15 Oct-28 Fri Inbound 1353 km flyby, v = 5.9 km/s, phase = 105 deg S15 17 Earth OCC TITAN T04:24 Oct-28 Fri Duration = 18 min; egress = T04:41 S15 17 SATURN Segment T09:49 Oct-29 Sat SATURN segment begins. Duration = 2 d S15 17 Tethys Dust Crxing T20:09 Oct-29 Sat End 302T20:33(00:24) No protection yet identified S15 17 Ring CRX Ascending T21:23 Oct-29 Sat r = 4.70 Rs S ME (nt) METHONE T21:38 Oct-29 Sat Inbound km flyby, v = 2.1 km/s, phase = 57 deg S15 17 Periapse T22:56 Oct-29 Sat Per = 29.0 d, inc = 0.4 deg, r = 4.6 Rs, phase = 92 deg S15 17 Tethys Dust Crxing T01:19 Oct-30 Sun End 303T01:43(00:24) No protection yet identified S CA (nt) CALYPSO T02:50 Oct-30 Sun Outbound km flyby, v = 9.4 km/s, phase = 66 deg S15 17 OTM TI T07:59 Oct-31 Mon D/L start, burn ~6h later. Backup D/L 299T01:14 S15 17 XDISC Segment T17:14 Oct-31 Mon XDISC segment begins. Duration = 25 d S15 17 Ring CRX Descending T16:24 Nov-05 Sat r = Rs S16 17 S16 Begins T17:01 Nov-12 Sat S16 Sequence. Duration = 35 d S16 18 Apoapse T04:57 Nov-13 Sun Per = 28.5 d, inc = 0.4 deg, r = 55.1 Rs, phase = 88 deg S16 18 OTM-042 ~APO T08:02 Nov-13 Sun D/L start, burn ~6h later. Backup D/L 305T08:30 S16 18 OTM RH T07:03 Nov-23 Wed D/L start, burn ~6h later. Backup D/L 318T08:02 S16 18 SOST Segment T15:48 Nov-25 Fri SOST segment begins. Duration = 4 d S RH (t) [R1] RHEA T22:38 Nov-26 Sat Inbound 500 km flyby, v = 7.3 km/s, phase = 87 deg S16 18 Tethys Dust Crxing T08:29 Nov-27 Sun End 331T08:53(00:23) No protection yet identified S16 18 Ring CRX Ascending T09:17 Nov-27 Sun r = 4.76 Rs S EN (nt) ENCELADUS T10:25 Nov-27 Sun Inbound km flyby, v = 7.5 km/s, phase = 134 deg S16 18 Periapse T11:21 Nov-27 Sun Per = 27.6 d, inc = 0.4 deg, r = 4.6 Rs, phase = 92 deg S16 18 Tethys Dust Crxing T13:50 Nov-27 Sun End 331T14:13(00:23) No protection yet identified S HE (nt) HELENE T14:36 Nov-27 Sun Outbound km flyby, v = 5.5 km/s, phase = 87 deg Page 6

22 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S16 18 OTM RH T22:15 Nov-27 Sun D/L start, burn ~6h later. Backup D/L 328T07:03 S16 18 XDISC Segment T15:33 Nov-29 Tue XDISC segment begins. Duration = 23 d S16 18 Ring CRX Descending T04:42 Dec-02 Fri r = Rs S16 19 Apoapse T04:27 Dec-11 Sun Per = 27.4 d, inc = 0.4 deg, r = 53.6 Rs, phase = 89 deg S16 19 OTM-045 ~APO T05:35 Dec-11 Sun D/L start, burn ~6h later. Backup D/L 333T06:33 S17 19 S17 Begins T14:21 Dec-17 Sat S17 Sequence. Duration = 41 d S17 19 MAG Segment T14:21 Dec-22 Thu MAG segment begins. Duration = 4 d S17 19 OTM TI T06:25 Dec-23 Fri D/L start, burn ~6h later. Backup D/L 346T05:35 S17 19 Mimas Dust Crxing T18:30 Dec-24 Sat End 358T18:54(00:23) No protection yet identified S17 19 Ring CRX Ascending T19:19 Dec-24 Sat r = 4.76 Rs S EN (nt) ENCELADUS T20:29 Dec-24 Sat Inbound km flyby, v = 6.7 km/s, phase = 133 deg S17 19 Periapse T21:23 Dec-24 Sat Per = 27.6 d, inc = 0.4 deg, r = 4.6 Rs, phase = 91 deg S PL (nt) PALLENE T22:26 Dec-24 Sat Outbound km flyby, v = 4.4 km/s, phase = 142 deg S17 19 E_ring_lg Dust Crxing T23:53 Dec-24 Sat End 359T00:16(00:23) No protection yet identified S TL (nt) TELESTO T00:44 Dec-25 Sun Outbound km flyby, v = 5.9 km/s, phase = 70 deg S HE (nt) HELENE T01:45 Dec-25 Sun Outbound km flyby, v = 5.4 km/s, phase = 90 deg S17 19 TOST Segment T06:59 Dec-26 Mon TOST segment begins. Duration = 1 d S TI (t) [T9] TITAN T18:59 Dec-26 Mon Outbound km flyby, v = 5.6 km/s, phase = 67 deg S17 19 XDISC Segment T13:34 Dec-27 Tue XDISC segment begins. Duration = 18 d S17 19 OTM TI T20:47 Dec-29 Thu D/L start, burn ~6h later. Backup D/L 358T04:40 S17 19 Ring CRX Descending T23:00 Dec-29 Thu r = Rs S17 19 OTM-048 ~APO T20:22 Jan-02 Mon D/L start, burn ~6h later. Backup D/L 365T04:07 S17 20 Apoapse T14:09 Jan-05 Thu Per = 23.4 d, inc = 0.4 deg, r = 48.3 Rs, phase = 94 deg S17 20 OTM TI T03:23 Jan-12 Thu D/L start, burn ~6h later. Backup D/L 004T04:17 S17 20 TOST Segment T13:38 Jan-14 Sat TOST segment begins. Duration = 2 d S TI (t) [T10] TITAN T11:41 Jan-15 Sun Inbound 2043 km flyby, v = 5.8 km/s, phase = 120 deg S17 20 Earth OCC TITAN T11:49 Jan-15 Sun Duration = 14 min; egress = T12:04 S17 20 Sun OCC TITAN T11:50 Jan-15 Sun Duration = 13 min; egress = T12:03 S17 20 TBD Segment T12:05 Jan-16 Mon TBD segment begins. Duration = 0 d S17 20 SOST Segment T13:46 Jan-16 Mon SOST segment begins. Duration = 3 d S17 20 Ring CRX Ascending T06:27 Jan-17 Tue r = 5.59 Rs S17 20 Periapse T06:58 Jan-17 Tue Per = 39.3 d, inc = 0.4 deg, r = 5.6 Rs, phase = 73 deg S17 20 OTM TI T02:29 Jan-18 Wed D/L start, burn ~6h later. Backup D/L 013T03:23 S17 20 XDISC Segment T11:59 Jan-19 Thu XDISC segment begins. Duration = 36 d S18 20 S18 Begins T04:03 Jan-27 Fri S18 Sequence. Duration = 43 d S18 20 OTM-051 ~APO T01:53 Feb-02 Thu D/L start, burn ~6h later. Backup D/L 019T02:44 S18 20 Ring CRX Descending T16:33 Feb-02 Thu r = Rs S18 21 Apoapse T20:58 Feb-05 Sun Per = 39.2 d, inc = 0.4 deg, r = 68.2 Rs, phase = 107 deg S18 21 SATURN Segment T09:22 Feb-24 Fri SATURN segment begins. Duration = 2 d S18 21 OTM TI T16:05 Feb-24 Fri D/L start, burn ~6h later. Backup D/L 034T01:38 S HE (nt) HELENE T04:47 Feb-25 Sat Inbound km flyby, v = 7.1 km/s, phase = 92 deg S18 21 Ring CRX Ascending T10:24 Feb-25 Sat r = 5.59 Rs S18 21 Periapse T10:56 Feb-25 Sat Per = 39.3 d, inc = 0.4 deg, r = 5.6 Rs, phase = 72 deg S18 21 TOST Segment T09:06 Feb-26 Sun TOST segment begins. Duration = 2 d S TI (t) [T11] TITAN T08:25 Feb-27 Mon Outbound 1813 km flyby, v = 5.9 km/s, phase = 92 deg S18 21 XDISC Segment T08:51 Feb-28 Tue XDISC segment begins. Duration = 18 d S18 21 OTM TI T23:51 Mar-01 Wed D/L start, burn ~6h later. Backup D/L 057T00:06 S18 21 OTM-054 ~APO T23:36 Mar-05 Sun D/L start, burn ~6h later. Backup D/L 061T16:21 S18 22 Apoapse T03:35 Mar-09 Thu Per = 23.3 d, inc = 0.4 deg, r = 48.4 Rs, phase = 122 deg S19 22 S19 Begins T00:35 Mar-11 Sat S19 Sequence. Duration = 42 d S19 22 Ring CRX Descending T15:48 Mar-12 Sun r = Rs S19 22 OTM TI T22:50 Mar-15 Wed D/L start, burn ~6h later. Backup D/L 065T15:51 S19 22 TOST Segment T07:49 Mar-18 Sat TOST segment begins. Duration = 2 d S19 22 Sun OCC TITAN T00:04 Mar-19 Sun Duration = 15 min; egress = T00:19 S19 22 Earth OCC TITAN T00:06 Mar-19 Sun Duration = 14 min; egress = T00:20 S TI (t) [T12] TITAN T00:06 Mar-19 Sun Inbound 1951 km flyby, v = 5.8 km/s, phase = 148 deg S19 22 SOST Segment T00:04 Mar-20 Mon SOST segment begins. Duration = 2 d S19 22 Periapse T20:05 Mar-20 Mon Per = 39.4 d, inc = 0.4 deg, r = 5.5 Rs, phase = 46 deg S19 22 Ring CRX Ascending T22:43 Mar-20 Mon r = 5.69 Rs S RH (nt) RHEA T07:16 Mar-21 Tue Outbound km flyby, v = 5.3 km/s, phase = 137 deg S19 22 OTM TI T22:19 Mar-21 Tue D/L start, burn ~6h later. Backup D/L 075T22:50 S19 22 XDISC Segment T07:19 Mar-22 Wed XDISC segment begins. Duration = 36 d S19 22 OTM-057 ~APO T21:32 Apr-05 Wed D/L start, burn ~6h later. Backup D/L 081T22:19 S19 23 Apoapse T10:04 Apr-09 Sun Per = 39.2 d, inc = 0.4 deg, r = 68.3 Rs, phase = 135 deg S20 23 S20 Begins T05:15 Apr-22 Sat S20 Sequence. Duration = 42 d Page 7

23 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S20 23 Ring CRX Descending T16:31 Apr-22 Sat r = Rs S20 23 OTM TI T19:59 Apr-26 Wed D/L start, burn ~6h later. Backup D/L 096T21:17 S20 23 SATURN Segment T04:59 Apr-27 Thu SATURN segment begins. Duration = 3 d S20 23 Periapse T23:59 Apr-28 Fri Per = 39.3 d, inc = 0.4 deg, r = 5.5 Rs, phase = 44 deg S20 23 Ring CRX Ascending T02:44 Apr-29 Sat r = 5.70 Rs S20 23 TOST Segment T04:44 Apr-30 Sun TOST segment begins. Duration = 2 d S TI (t) [T13] TITAN T20:58 Apr-30 Sun Outbound 1855 km flyby, v = 5.8 km/s, phase = 121 deg S20 23 Sun OCC TITAN T21:05 Apr-30 Sun Duration = 16 min; egress = T21:22 S20 23 Earth OCC TITAN T21:11 Apr-30 Sun Duration = 7 min; egress = T21:18 S20 23 XDISC Segment T21:14 May-01 Mon XDISC segment begins. Duration = 18 d S20 23 OTM TI T19:28 May-03 Wed D/L start, burn ~6h later. Backup D/L 117T19:59 S20 23 OTM-060 ~APO T19:13 May-07 Sun D/L start, burn ~6h later. Backup D/L 124T20:58 S20 24 Apoapse T16:31 May-10 Wed Per = 23.3 d, inc = 0.4 deg, r = 48.4 Rs, phase = 148 deg S20 24 OTM TI T18:41 May-17 Wed D/L start, burn ~6h later. Backup D/L 128T11:43 S20 24 TOST Segment T19:56 May-19 Fri TOST segment begins. Duration = 2 d S20 24 Ring CRX Descending T05:31 May-20 Sat r = Rs S20 24 Sun OCC TITAN T12:11 May-20 Sat Duration = 14 min; egress = T12:25 S20 24 Earth OCC TITAN T12:12 May-20 Sat Duration = 14 min; egress = T12:26 S TI (t) [T14] TITAN T12:18 May-20 Sat Inbound 1879 km flyby, v = 5.8 km/s, phase = 163 deg S20 24 SATURN Segment T19:56 May-21 Sun SATURN segment begins. Duration = 2 d S20 24 Periapse T09:01 May-22 Mon Per = 39.4 d, inc = 0.4 deg, r = 5.5 Rs, phase = 21 deg S20 24 Dione Dust Hazard T14:00 May-22 Mon End 142T14:33(00:32) MEA cover closed S PO (nt) POLYDEUCES T14:53 May-22 Mon Outbound km flyby, v = 6.9 km/s, phase = 19 deg S20 24 Ring CRX Ascending T15:14 May-22 Mon r = 6.54 Rs S20 24 OTM TI T10:41 May-23 Tue D/L start, burn ~6h later. Backup D/L 138T18:41 S20 24 XDISC Segment T19:41 May-23 Tue XDISC segment begins. Duration = 35 d S21 24 S21 Begins T02:39 Jun-03 Sat S21 Sequence. Duration = 44 d S21 24 OTM-063 ~APO T17:24 Jun-07 Wed D/L start, burn ~6h later. Backup D/L 144T18:11 S21 25 Apoapse T23:07 Jun-10 Sat Per = 39.2 d, inc = 0.4 deg, r = 68.3 Rs, phase = 159 deg S21 25 SATURN Segment T01:07 Jun-28 Wed SATURN segment begins. Duration = 4 d S21 25 OTM TI T16:07 Jun-28 Wed D/L start, burn ~6h later. Backup D/L 159T17:09 S21 25 Ring CRX Descending T01:49 Jun-29 Thu r = Rs S21 25 Periapse T13:05 Jun-30 Fri Per = 39.3 d, inc = 0.4 deg, r = 5.4 Rs, phase = 20 deg S21 25 G_ring Dust Hazard T18:27 Jun-30 Fri End 181T18:39(00:11) MEA cover closed S21 25 Ring CRX Ascending T20:55 Jun-30 Fri r = 7.06 Rs S21 25 TOST Segment T17:22 Jul-01 Sat TOST segment begins. Duration = 2 d S21 25 Sun OCC TITAN T09:20 Jul-02 Sun Duration = 15 min; egress = T09:35 S21 25 Earth OCC TITAN T09:20 Jul-02 Sun Duration = 15 min; egress = T09:35 S TI (t) [T15] TITAN T09:21 Jul-02 Sun Outbound 1906 km flyby, v = 5.8 km/s, phase = 148 deg S21 25 XDISC Segment T17:22 Jul-03 Mon XDISC segment begins. Duration = 17 d S21 25 OTM TI T15:36 Jul-05 Wed D/L start, burn ~6h later. Backup D/L 180T08:37 S21 25 OTM-066 ~APO T15:21 Jul-10 Mon D/L start, burn ~6h later. Backup D/L 187T15:36 S21 26 Apoapse T05:18 Jul-12 Wed Per = 23.3 d, inc = 0.4 deg, r = 48.4 Rs, phase = 164 deg S22 26 S22 Begins T00:06 Jul-17 Mon S22 Sequence. Duration = 34 d S22 26 OTM TI T14:51 Jul-18 Tue D/L start, burn ~6h later. Backup D/L 192T15:21 S22 26 TOST Segment T23:51 Jul-20 Thu TOST segment begins. Duration = 2 d S TI (t) [T16] TITAN T00:25 Jul-22 Sat Inbound 950 km flyby, v = 6.0 km/s, phase = 105 deg S22 26 Ring CRX Descending T02:36 Jul-22 Sat r = Rs S22 26 RINGS Segment T23:36 Jul-22 Sat RINGS segment begins. Duration = 4 d S TE (nt) TETHYS T17:18 Jul-23 Sun Inbound km flyby, v = 9.9 km/s, phase = 29 deg S22 26 Periapse T21:48 Jul-23 Sun Per = 24.1 d, inc = 15.0 deg, r = 4.2 Rs, phase = 8 deg S22 26 Ring CRX Ascending T01:15 Jul-24 Mon r = 4.77 Rs S22 26 Mimas Dust Crxing T01:28 Jul-24 Mon End 205T01:40(00:11) No protection yet identified S TL (nt) TELESTO T01:58 Jul-24 Mon Outbound km flyby, v = 8.6 km/s, phase = 39 deg S22 26 OTM TI T14:30 Jul-24 Mon D/L start, burn ~6h later. Backup D/L 200T14:51 S22 26 XDISC Segment T23:21 Jul-26 Wed XDISC segment begins. Duration = 18 d S22 26 OTM-069 ~APO T14:05 Aug-01 Tue D/L start, burn ~6h later. Backup D/L 206T14:30 S22 26 SEP = 3.0 [deg] Conjunction T00:00 Aug-03 Thu Commanding must not be required below 3.0 deg S22 27 Apoapse T21:25 Aug-04 Fri Per = 24.0 d, inc = 14.9 deg, r = 49.0 Rs, phase = 172 deg S22 27 SEP = 2.0 [deg] Conjunction T06:47 Aug-05 Sat Plan no SSR playback below 2.0 deg S22 27 SEP = 1.0 [deg] Conjunction T18:34 Aug-06 Sun Require no DSN passes below 1.0 deg S22 27 SEP = 1.0 [deg] Conjunction T05:42 Aug-08 Tue Require no DSN passes below 1.0 deg S22 27 SEP = 2.0 [deg] Conjunction T17:27 Aug-09 Wed Plan no SSR playback below 2.0 deg S22 27 SEP = 3.0 [deg] Conjunction T00:09 Aug-11 Fri Commanding must not be required below 3.0 deg S22 27 SATURN Segment T22:12 Aug-13 Sun SATURN segment begins. Duration = 6 d S22 27 Ring CRX Descending T02:15 Aug-15 Tue r = Rs Page 8

24 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S22 27 Periapse T20:54 Aug-16 Wed Per = 24.1 d, inc = 14.9 deg, r = 4.2 Rs, phase = 8 deg S22 27 Ring CRX Ascending T00:20 Aug-17 Thu r = 4.75 Rs S _Rs Dust Crxing T00:37 Aug-17 Thu End 229T00:45(00:08) No protection yet identified S HE (nt) HELENE T03:29 Aug-17 Thu Outbound km flyby, v = 7.7 km/s, phase = 123 deg S TI (nt) TITAN T17:51 Aug-18 Fri Outbound km flyby, v = 4.8 km/s, phase = 121 deg S23 27 XDISC Segment T22:06 Aug-19 Sat XDISC segment begins. Duration = 18 d S23 27 S23 Begins T22:06 Aug-19 Sat S23 Sequence. Duration = 32 d S23 28 Apoapse T19:13 Aug-28 Mon Per = 23.9 d, inc = 14.9 deg, r = 48.8 Rs, phase = 172 deg S23 28 OTM TI T12:21 Sep-04 Mon D/L start, burn ~6h later. Backup D/L 214T14:05 S23 28 TOST Segment T21:06 Sep-06 Wed TOST segment begins. Duration = 2 d S TI (t) [T17] TITAN T20:13 Sep-07 Thu Inbound 950 km flyby, v = 6.0 km/s, phase = 45 deg S23 28 Ring CRX Descending T21:18 Sep-07 Thu r = Rs S23 28 RINGS Segment T21:06 Sep-08 Fri RINGS segment begins. Duration = 3 d S AT (nt) ATLAS T17:32 Sep-09 Sat Inbound km flyby, v = 14.8 km/s, phase = 46 deg S23 28 Periapse T17:38 Sep-09 Sat Per = 16.2 d, inc = 24.9 deg, r = 2.9 Rs, phase = 7 deg S23 28 E_ring_lg Dust Crxing T18:50 Sep-09 Sat End 252T19:01(00:10) No protection yet identified S23 28 Ring CRX Ascending T19:01 Sep-09 Sat r = 3.14 Rs S ME (nt) METHONE T19:11 Sep-09 Sat Outbound km flyby, v = 10.1 km/s, phase = 71 deg S CA (nt) CALYPSO T19:15 Sep-09 Sat Outbound km flyby, v = 9.8 km/s, phase = 162 deg S EN (nt) ENCELADUS T19:58 Sep-09 Sat Outbound km flyby, v = 10.3 km/s, phase = 118 deg S23 28 OTM TI T12:00 Sep-10 Sun D/L start, burn ~6h later. Backup D/L 248T12:06 S23 28 SATURN Segment T21:00 Sep-11 Mon SATURN segment begins. Duration = 1 d S23 28 MAG Segment T21:00 Sep-12 Tue MAG segment begins. Duration = 2 d S23 28 OTM-072 ~APO T04:07 Sep-14 Thu D/L start, burn ~6h later. Backup D/L 254T12:00 S23 28 Sun OCC RING T17:08 Sep-14 Thu Duration = 1501 min; egress = T18:09 S23 28 Sun OCC RING T17:08 Sep-14 Thu Duration = 1501 min; egress = T18:09 S23 28 RINGS Segment T19:22 Sep-14 Thu RINGS segment begins. Duration = 3 d S23 28 Sun OCC SATURN T06:58 Sep-15 Fri Duration = 964 min; egress = T23:01 S23 28 Earth OCC RING T17:54 Sep-15 Fri Duration = 1653 min; egress = T21:28 S23 28 Earth OCC RING T17:54 Sep-15 Fri Duration = 1653 min; egress = T21:28 S23 28 Earth OCC SATURN T04:54 Sep-16 Sat Duration = 1188 min; egress = T00:42 S23 28 XDISC Segment T14:07 Sep-17 Sun XDISC segment begins. Duration = 5 d S23 29 Apoapse T17:07 Sep-17 Sun Per = 15.9 d, inc = 24.7 deg, r = 37.6 Rs, phase = 173 deg S23 29 OTM TI T11:22 Sep-20 Wed D/L start, burn ~6h later. Backup D/L 257T10:22 S24 29 S24 Begins T20:22 Sep-20 Wed S24 Sequence. Duration = 32 d S24 29 TOST Segment T20:07 Sep-22 Fri TOST segment begins. Duration = 2 d S TI (t) [T18] TITAN T18:55 Sep-23 Sat Inbound 950 km flyby, v = 6.0 km/s, phase = 90 deg S24 29 Ring CRX Descending T19:51 Sep-23 Sat r = Rs S24 29 RINGS Segment T20:00 Sep-24 Sun RINGS segment begins. Duration = 4 d S24 29 Periapse T19:32 Sep-25 Mon Per = 16.0 d, inc = 37.8 deg, r = 4.0 Rs, phase = 7 deg S ME (nt) METHONE T21:40 Sep-25 Mon Outbound km flyby, v = 10.0 km/s, phase = 46 deg S24 29 E_ring_lg Dust Crxing T22:07 Sep-25 Mon End 268T22:09(00:01) No protection yet identified S24 29 Ring CRX Ascending T22:08 Sep-25 Mon r = 4.32 Rs S24 29 OTM TI T11:30 Sep-26 Tue D/L start, burn ~6h later. Backup D/L 264T11:22 S24 29 XDISC Segment T19:53 Sep-28 Thu XDISC segment begins. Duration = 10 d S24 29 OTM-075 ~APO T03:08 Oct-01 Sun D/L start, burn ~6h later. Backup D/L 270T11:30 S24 30 Apoapse T18:53 Oct-03 Tue Per = 15.9 d, inc = 37.8 deg, r = 36.5 Rs, phase = 173 deg S24 30 OTM TI T10:24 Oct-06 Fri D/L start, burn ~6h later. Backup D/L 275T10:38 S24 30 TOST Segment T19:24 Oct-08 Sun TOST segment begins. Duration = 2 d S TI (t) [T19] TITAN T17:26 Oct-09 Mon Inbound 950 km flyby, v = 6.0 km/s, phase = 81 deg S24 30 Ring CRX Descending T18:05 Oct-09 Mon r = Rs S24 30 SATURN Segment T19:00 Oct-10 Tue SATURN segment begins. Duration = 1 d S24 30 RINGS Segment T19:09 Oct-11 Wed RINGS segment begins. Duration = 4 d S24 30 Periapse T22:51 Oct-11 Wed Per = 15.9 d, inc = 46.9 deg, r = 5.5 Rs, phase = 14 deg S24 30 Ring CRX Ascending T04:04 Oct-12 Thu r = 6.17 Rs S24 30 OTM TI T10:10 Oct-12 Thu D/L start, burn ~6h later. Backup D/L 280T10:24 S24 30 XDISC Segment T18:55 Oct-15 Sun XDISC segment begins. Duration = 8 d S24 30 OTM-078 ~APO T09:40 Oct-17 Tue D/L start, burn ~6h later. Backup D/L 286T09:55 S24 31 Apoapse T22:09 Oct-19 Thu Per = 15.9 d, inc = 46.9 deg, r = 35.0 Rs, phase = 166 deg S24 31 OTM TI T09:26 Oct-22 Sun D/L start, burn ~6h later. Backup D/L 291T02:10 S25 31 S25 Begins T18:26 Oct-22 Sun S25 Sequence. Duration = 33 d S25 31 TOST Segment T10:56 Oct-23 Mon TOST segment begins. Duration = 3 d S TI (t) [T20] TITAN T15:54 Oct-25 Wed Inbound 950 km flyby, v = 6.0 km/s, phase = 25 deg S25 31 Ring CRX Descending T16:15 Oct-25 Wed r = Rs S25 31 RINGS Segment T18:11 Oct-26 Thu RINGS segment begins. Duration = 3 d S25 31 Periapse T00:17 Oct-28 Sat Per = 12.0 d, inc = 55.4 deg, r = 4.7 Rs, phase = 16 deg Page 9

25 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S25 31 Ring CRX Ascending T03:19 Oct-28 Sat r = 5.02 Rs S TL (nt) TELESTO T04:12 Oct-28 Sat Outbound km flyby, v = 12.1 km/s, phase = 111 deg S25 31 SATURN Segment T10:42 Oct-29 Sun SATURN segment begins. Duration = 2 d S25 31 XDISC Segment T17:57 Oct-31 Tue XDISC segment begins. Duration = 5 d S25 32 Apoapse T00:10 Nov-03 Fri Per = 12.0 d, inc = 55.4 deg, r = 28.8 Rs, phase = 164 deg S25 32 RINGS Segment T17:42 Nov-05 Sun RINGS segment begins. Duration = 5 d S25 32 Ring CRX Descending T15:48 Nov-06 Mon r = Rs S25 32 Periapse T00:03 Nov-09 Thu Per = 12.0 d, inc = 55.4 deg, r = 4.7 Rs, phase = 16 deg S EN (nt) ENCELADUS T01:49 Nov-09 Thu Outbound km flyby, v = 14.1 km/s, phase = 27 deg S25 32 Ring CRX Ascending T03:05 Nov-09 Thu r = 5.02 Rs S CA (nt) CALYPSO T03:52 Nov-09 Thu Outbound km flyby, v = 11.8 km/s, phase = 110 deg S25 32 OTM-080 ~PERI T08:28 Nov-09 Thu D/L start, burn ~6h later. Backup D/L 296T01:56 S25 32 SATURN Segment T09:58 Nov-10 Fri SATURN segment begins. Duration = 2 d S25 32 XDISC Segment T17:13 Nov-12 Sun XDISC segment begins. Duration = 5 d S25 33 Apoapse T23:34 Nov-14 Tue Per = 12.0 d, inc = 55.4 deg, r = 28.7 Rs, phase = 164 deg S25 33 RINGS Segment T16:59 Nov-17 Fri RINGS segment begins. Duration = 7 d S25 33 Ring CRX Descending T15:02 Nov-18 Sat r = Rs S25 33 Periapse T23:06 Nov-20 Mon Per = 12.0 d, inc = 55.4 deg, r = 4.7 Rs, phase = 16 deg S25 33 Ring CRX Ascending T02:08 Nov-21 Tue r = 5.02 Rs S DI (nt) DIONE T02:34 Nov-21 Tue Outbound km flyby, v = 12.3 km/s, phase = 144 deg S TI (nt) TITAN T13:34 Nov-21 Tue Outbound km flyby, v = 8.1 km/s, phase = 77 deg S26 33 XDISC Segment T16:30 Nov-24 Fri XDISC segment begins. Duration = 5 d S26 33 S26 Begins T16:30 Nov-24 Fri S26 Sequence. Duration = 42 d S TI (nt) TITAN T14:02 Nov-25 Sat Outbound km flyby, v = 4.5 km/s, phase = 114 deg S26 33 OTM-081 ~APO T07:15 Nov-26 Sun D/L start, burn ~6h later. Backup D/L 314T00:58 S26 34 Apoapse T22:24 Nov-26 Sun Per = 11.9 d, inc = 55.4 deg, r = 28.7 Rs, phase = 164 deg S26 34 RINGS Segment T16:16 Nov-29 Wed RINGS segment begins. Duration = 2 d S26 34 Ring CRX Descending T13:38 Nov-30 Thu r = Rs S26 34 SATURN Segment T08:31 Dec-01 Fri SATURN segment begins. Duration = 1 d S26 34 RINGS Segment T08:31 Dec-02 Sat RINGS segment begins. Duration = 4 d S26 34 Periapse T21:44 Dec-02 Sat Per = 12.0 d, inc = 55.5 deg, r = 4.7 Rs, phase = 16 deg S TI (nt) TITAN T23:27 Dec-02 Sat Outbound km flyby, v = 12.1 km/s, phase = 159 deg S26 34 Ring CRX Ascending T00:46 Dec-03 Sun r = 5.02 Rs S TL (nt) TELESTO T01:27 Dec-03 Sun Outbound km flyby, v = 12.2 km/s, phase = 109 deg S26 34 XDISC Segment T15:47 Dec-06 Wed XDISC segment begins. Duration = 5 d S26 35 Apoapse T21:07 Dec-08 Fri Per = 12.0 d, inc = 55.4 deg, r = 28.7 Rs, phase = 164 deg S26 35 OTM TI T06:32 Dec-09 Sat D/L start, burn ~6h later. Backup D/L 331T07:15 S26 35 TOST Segment T15:17 Dec-11 Mon TOST segment begins. Duration = 2 d S TI (t) [T21] TITAN T11:37 Dec-12 Tue Inbound 950 km flyby, v = 6.0 km/s, phase = 124 deg S26 35 Ring CRX Descending T12:06 Dec-12 Tue r = Rs S26 35 SATURN Segment T07:48 Dec-13 Wed SATURN segment begins. Duration = 1 d S26 35 RINGS Segment T06:48 Dec-14 Thu RINGS segment begins. Duration = 4 d S26 35 Periapse T00:18 Dec-15 Fri Per = 15.9 d, inc = 53.3 deg, r = 7.7 Rs, phase = 24 deg S26 35 OTM TI T06:03 Dec-15 Fri D/L start, burn ~6h later. Backup D/L 344T06:32 S26 35 Ring CRX Ascending T11:12 Dec-15 Fri r = 8.94 Rs S26 35 XDISC Segment T15:03 Dec-18 Mon XDISC segment begins. Duration = 9 d S26 35 OTM-084 ~APO T05:48 Dec-20 Wed D/L start, burn ~6h later. Backup D/L 350T05:45 S26 36 Apoapse T23:28 Dec-22 Fri Per = 15.9 d, inc = 53.3 deg, r = 32.8 Rs, phase = 156 deg S26 36 OTM TI T05:34 Dec-25 Mon D/L start, burn ~6h later. Backup D/L 355T05:49 S26 36 TOST Segment T14:19 Dec-27 Wed TOST segment begins. Duration = 2 d S TI (t) [T22] TITAN T10:02 Dec-28 Thu Inbound 1500 km flyby, v = 5.9 km/s, phase = 62 deg S26 36 Ring CRX Descending T10:27 Dec-28 Thu r = Rs S26 36 RINGS Segment T06:49 Dec-29 Fri RINGS segment begins. Duration = 6 d S26 36 OTM TI T05:05 Dec-31 Sun D/L start, burn ~6h later. Backup D/L 360T05:19 S26 36 Periapse T05:16 Dec-31 Sun Per = 15.9 d, inc = 56.8 deg, r = 9.8 Rs, phase = 31 deg S26 36 Ring CRX Ascending T23:58 Dec-31 Sun r = Rs S26 36 XDISC Segment T13:50 Jan-04 Thu XDISC segment begins. Duration = 8 d S26 36 OTM-087 ~APO T04:50 Jan-05 Fri D/L start, burn ~6h later. Backup D/L 001T05:05 S27 36 S27 Begins T13:50 Jan-05 Fri S27 Sequence. Duration = 43 d S27 37 Apoapse T04:38 Jan-08 Mon Per = 16.0 d, inc = 56.8 deg, r = 30.7 Rs, phase = 148 deg S27 37 OTM TI T04:20 Jan-10 Wed D/L start, burn ~6h later. Backup D/L 006T04:35 S27 37 TOST Segment T13:34 Jan-12 Fri TOST segment begins. Duration = 2 d S TI (t) [T23] TITAN T08:36 Jan-13 Sat Inbound 950 km flyby, v = 6.0 km/s, phase = 53 deg S27 37 Ring CRX Descending T08:55 Jan-13 Sat r = Rs Page 10

26 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S27 37 SATURN Segment T13:34 Jan-14 Sun SATURN segment begins. Duration = 1 d S27 37 RINGS Segment T05:36 Jan-15 Mon RINGS segment begins. Duration = 6 d S27 37 OTM TI T20:36 Jan-15 Mon D/L start, burn ~6h later. Backup D/L 011T04:21 S27 37 Periapse T13:07 Jan-16 Tue Per = 16.0 d, inc = 59.4 deg, r = 12.6 Rs, phase = 40 deg S27 37 Ring CRX Ascending T21:24 Jan-17 Wed r = Rs S27 37 OTM-090 ~APO T03:36 Jan-21 Sun D/L start, burn ~6h later. Backup D/L 017T03:51 S27 37 XDISC Segment T12:36 Jan-21 Sun XDISC segment begins. Duration = 7 d S27 38 Apoapse T12:27 Jan-24 Wed Per = 16.0 d, inc = 59.4 deg, r = 27.9 Rs, phase = 140 deg S27 38 OTM TI T03:21 Jan-26 Fri D/L start, burn ~6h later. Backup D/L 022T03:36 S27 38 TOST Segment T12:12 Jan-28 Sun TOST segment begins. Duration = 2 d S TI (t) [T24] TITAN T07:14 Jan-29 Mon Inbound 2726 km flyby, v = 5.8 km/s, phase = 72 deg S27 38 Ring CRX Descending T07:36 Jan-29 Mon r = Rs S27 38 SATURN Segment T12:12 Jan-30 Tue SATURN segment begins. Duration = 7 d S27 38 OTM TI T02:52 Feb-01 Thu D/L start, burn ~6h later. Backup D/L 027T03:21 S27 38 Periapse T09:55 Feb-01 Thu Per = 18.1 d, inc = 59.0 deg, r = 15.6 Rs, phase = 58 deg S27 38 Ring CRX Ascending T01:07 Feb-04 Sun r = Rs S TI (nt) TITAN T07:38 Feb-05 Mon Outbound km flyby, v = 5.9 km/s, phase = 114 deg S27 38 XDISC Segment T11:37 Feb-06 Tue XDISC segment begins. Duration = 8 d S27 38 OTM-093 ~APO T02:37 Feb-07 Wed D/L start, burn ~6h later. Backup D/L 033T19:22 S27 39 Apoapse T10:51 Feb-10 Sat Per = 18.1 d, inc = 59.0 deg, r = 28.5 Rs, phase = 121 deg S27 39 RINGS Segment T09:45 Feb-14 Wed RINGS segment begins. Duration = 7 d S TI (nt) TITAN T03:09 Feb-15 Thu Inbound km flyby, v = 5.5 km/s, phase = 128 deg S27 39 Ring CRX Descending T09:42 Feb-16 Fri r = Rs S28 39 S28 Begins T10:52 Feb-17 Sat S28 Sequence. Duration = 39 d S28 39 OTM TI T01:37 Feb-19 Mon D/L start, burn ~6h later. Backup D/L 039T02:22 S28 39 Periapse T11:47 Feb-19 Mon Per = 18.1 d, inc = 59.0 deg, r = 15.6 Rs, phase = 59 deg S28 39 TOST Segment T10:37 Feb-21 Wed TOST segment begins. Duration = 2 d S28 39 Sun OCC TITAN T02:59 Feb-22 Thu Duration = 16 min; egress = T03:15 S28 39 Earth OCC TITAN T03:00 Feb-22 Thu Duration = 16 min; egress = T03:15 S TI (t) [T25] TITAN T03:10 Feb-22 Thu Outbound 950 km flyby, v = 6.3 km/s, phase = 161 deg S28 39 Ring CRX Ascending T03:15 Feb-22 Thu r = Rs S28 39 XDISC Segment T10:11 Feb-23 Fri XDISC segment begins. Duration = 7 d S28 39 OTM TI T01:22 Feb-25 Sun D/L start, burn ~6h later. Backup D/L 051T01:37 S28 40 Apoapse T07:48 Feb-27 Tue Per = 16.0 d, inc = 58.8 deg, r = 28.4 Rs, phase = 97 deg S28 40 OTM-096 ~APO T00:51 Mar-02 Fri D/L start, burn ~6h later. Backup D/L 057T01:06 S28 40 SATURN Segment T09:51 Mar-02 Fri SATURN segment begins. Duration = 7 d S28 40 Ring CRX Descending T21:15 Mar-05 Mon r = Rs S28 40 OTM TI T17:06 Mar-06 Tue D/L start, burn ~6h later. Backup D/L 062T00:51 S28 40 Periapse T07:11 Mar-07 Wed Per = 15.9 d, inc = 58.8 deg, r = 12.1 Rs, phase = 83 deg S28 40 TOST Segment T09:21 Mar-09 Fri TOST segment begins. Duration = 2 d S28 40 Sun OCC TITAN T01:35 Mar-10 Sat Duration = 16 min; egress = T01:50 S28 40 Earth OCC TITAN T01:35 Mar-10 Sat Duration = 15 min; egress = T01:50 S TI (t) [T26] TITAN T01:47 Mar-10 Sat Outbound 950 km flyby, v = 6.3 km/s, phase = 149 deg S28 40 Ring CRX Ascending T01:52 Mar-10 Sat r = Rs S28 40 XDISC Segment T02:47 Mar-11 Sun XDISC segment begins. Duration = 8 d S28 40 OTM TI T00:06 Mar-13 Tue D/L start, burn ~6h later. Backup D/L 067T00:21 S28 41 Apoapse T12:41 Mar-15 Thu Per = 15.9 d, inc = 56.2 deg, r = 30.8 Rs, phase = 88 deg S28 41 OTM-099 ~APO T23:50 Mar-17 Sat D/L start, burn ~6h later. Backup D/L 073T00:06 S28 41 RINGS Segment T08:35 Mar-19 Mon RINGS segment begins. Duration = 6 d S28 41 OTM TI T14:30 Mar-22 Thu D/L start, burn ~6h later. Backup D/L 077T23:35 S28 41 Ring CRX Descending T16:02 Mar-22 Thu r = Rs S28 41 Periapse T12:02 Mar-23 Fri Per = 15.9 d, inc = 56.2 deg, r = 9.7 Rs, phase = 92 deg S28 41 TOST Segment T08:20 Mar-25 Sun TOST segment begins. Duration = 2 d S28 41 Sun OCC TITAN T00:07 Mar-26 Mon Duration = 18 min; egress = T00:24 S28 41 Earth OCC TITAN T00:07 Mar-26 Mon Duration = 16 min; egress = T00:24 S TI (t) [T27] TITAN T00:22 Mar-26 Mon Outbound 950 km flyby, v = 6.3 km/s, phase = 144 deg S28 41 Ring CRX Ascending T00:26 Mar-26 Mon r = Rs S28 41 XDISC Segment T07:22 Mar-27 Tue XDISC segment begins. Duration = 9 d S29 41 S29 Begins T08:04 Mar-28 Wed S29 Sequence. Duration = 38 d S29 41 OTM TI T14:49 Mar-28 Wed D/L start, burn ~6h later. Backup D/L 082T23:20 S29 42 Apoapse T17:09 Mar-31 Sat Per = 15.9 d, inc = 52.4 deg, r = 33.0 Rs, phase = 80 deg S29 42 OTM-102 ~APO T22:34 Apr-02 Mon D/L start, burn ~6h later. Backup D/L 088T22:49 S29 42 SATURN Segment T07:33 Apr-05 Thu SATURN segment begins. Duration = 3 d S29 42 OTM TI T14:48 Apr-07 Sat D/L start, burn ~6h later. Backup D/L 093T22:33 S29 42 RINGS Segment T23:48 Apr-07 Sat RINGS segment begins. Duration = 2 d Page 11

27 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S29 42 Ring CRX Descending T05:19 Apr-08 Sun r = 8.87 Rs S29 42 Periapse T16:30 Apr-08 Sun Per = 15.9 d, inc = 52.4 deg, r = 7.5 Rs, phase = 100 deg S29 42 TOST Segment T07:03 Apr-10 Tue TOST segment begins. Duration = 2 d S29 42 Sun OCC TITAN T22:38 Apr-10 Tue Duration = 20 min; egress = T22:58 S29 42 Earth OCC TITAN T22:39 Apr-10 Tue Duration = 18 min; egress = T22:58 S TI (t) [T28] TITAN T22:56 Apr-10 Tue Outbound 950 km flyby, v = 6.3 km/s, phase = 137 deg S29 42 Ring CRX Ascending T23:00 Apr-10 Tue r = Rs S29 42 XDISC Segment T05:57 Apr-12 Thu XDISC segment begins. Duration = 9 d S29 42 OTM TI T21:47 Apr-13 Fri D/L start, burn ~6h later. Backup D/L 098T22:18 S29 43 Apoapse T20:52 Apr-16 Mon Per = 15.9 d, inc = 46.9 deg, r = 34.8 Rs, phase = 73 deg S29 43 OTM-105 ~APO T21:32 Apr-18 Wed D/L start, burn ~6h later. Backup D/L 104T21:47 S29 43 RINGS Segment T06:16 Apr-21 Sat RINGS segment begins. Duration = 5 d S29 43 OTM TI T21:16 Apr-23 Mon D/L start, burn ~6h later. Backup D/L 109T21:32 S29 43 Earth OCC RING T09:30 Apr-24 Tue Duration = 86 min; egress = T10:56 S29 43 Sun OCC RING T10:13 Apr-24 Tue Duration = 100 min; egress = T11:52 S29 43 Ring CRX Descending T14:14 Apr-24 Tue r = 6.48 Rs S DI (nt) DIONE T15:01 Apr-24 Tue Inbound km flyby, v = 11.3 km/s, phase = 68 deg S TL (nt) TELESTO T16:05 Apr-24 Tue Inbound km flyby, v = 11.0 km/s, phase = 104 deg S29 43 Periapse T20:13 Apr-24 Tue Per = 16.0 d, inc = 46.9 deg, r = 5.7 Rs, phase = 107 deg S29 43 TOST Segment T06:01 Apr-26 Thu TOST segment begins. Duration = 2 d S29 43 Sun OCC TITAN T21:09 Apr-26 Thu Duration = 22 min; egress = T21:32 S29 43 Earth OCC TITAN T21:11 Apr-26 Thu Duration = 22 min; egress = T21:32 S TI (t) [T29] TITAN T21:31 Apr-26 Thu Outbound 950 km flyby, v = 6.3 km/s, phase = 130 deg S29 43 Ring CRX Ascending T21:34 Apr-26 Thu r = Rs S29 43 XDISC Segment T22:33 Apr-27 Fri XDISC segment begins. Duration = 9 d S29 43 OTM TI T20:45 Apr-29 Sun D/L start, burn ~6h later. Backup D/L 114T21:01 S29 44 Apoapse T23:33 May-02 Wed Per = 15.9 d, inc = 39.0 deg, r = 36.3 Rs, phase = 66 deg S29 44 OTM-108 ~APO T13:00 May-04 Fri D/L start, burn ~6h later. Backup D/L 120T20:45 S30 44 S30 Begins T22:00 May-04 Fri S30 Sequence. Duration = 37 d S30 44 RINGS Segment T05:14 May-07 Mon RINGS segment begins. Duration = 3 d S30 44 OTM TI T20:14 May-08 Tue D/L start, burn ~6h later. Backup D/L 125T20:29 S30 44 SATURN Segment T05:14 May-10 Thu SATURN segment begins. Duration = 2 d S30 44 Earth OCC SATURN T14:55 May-10 Thu Duration = 126 min; egress = T17:01 S30 44 Earth OCC RING T15:39 May-10 Thu Duration = 154 min; egress = T18:13 S30 44 Sun OCC SATURN T15:43 May-10 Thu Duration = 136 min; egress = T17:58 S30 44 Sun OCC RING T16:33 May-10 Thu Duration = 124 min; egress = T18:36 S30 44 Ring CRX Descending T19:46 May-10 Thu r = 4.68 Rs S30 44 Periapse T22:55 May-10 Thu Per = 16.0 d, inc = 39.1 deg, r = 4.2 Rs, phase = 114 deg S30 44 TOST Segment T04:59 May-12 Sat TOST segment begins. Duration = 2 d S30 44 Sun OCC TITAN T19:40 May-12 Sat Duration = 26 min; egress = T20:06 S30 44 Earth OCC TITAN T19:41 May-12 Sat Duration = 26 min; egress = T20:07 S TI (t) [T30] TITAN T20:08 May-12 Sat Outbound 950 km flyby, v = 6.3 km/s, phase = 121 deg S30 44 Ring CRX Ascending T20:09 May-12 Sat r = Rs S30 44 XDISC Segment T21:13 May-13 Sun XDISC segment begins. Duration = 10 d S30 44 OTM TI T19:43 May-15 Tue D/L start, burn ~6h later. Backup D/L 129T20:14 S30 45 Apoapse T01:10 May-19 Sat Per = 16.0 d, inc = 28.0 deg, r = 37.3 Rs, phase = 61 deg S30 45 OTM-111 ~APO T19:27 May-20 Sun D/L start, burn ~6h later. Backup D/L 136T19:43 S30 45 SATURN Segment T04:12 May-24 Thu SATURN segment begins. Duration = 2 d S30 45 OTM TI T19:12 May-25 Fri D/L start, burn ~6h later. Backup D/L 141T11:42 S30 45 SOST Segment T04:12 May-26 Sat SOST segment begins. Duration = 2 d S30 45 Earth OCC RING T18:59 May-26 Sat Duration = 186 min; egress = T22:05 S30 45 Earth OCC SATURN T19:20 May-26 Sat Duration = 144 min; egress = T21:43 S30 45 Sun OCC RING T19:51 May-26 Sat Duration = 145 min; egress = T22:17 S30 45 Sun OCC SATURN T19:56 May-26 Sat Duration = 136 min; egress = T22:11 S TE (nt) TETHYS T20:57 May-26 Sat Inbound km flyby, v = 11.7 km/s, phase = 75 deg S30 45 Ring CRX Descending T22:53 May-26 Sat r = 3.44 Rs S EP (nt) EPIMETHEUS T23:16 May-26 Sat Inbound km flyby, v = 8.6 km/s, phase = 156 deg S30 45 Periapse T00:36 May-27 Sun Per = 16.1 d, inc = 28.2 deg, r = 3.2 Rs, phase = 119 deg S30 45 TOST Segment T03:56 May-28 Mon TOST segment begins. Duration = 2 d S30 45 Sun OCC TITAN T18:07 May-28 Mon Duration = 32 min; egress = T18:39 S30 45 Earth OCC TITAN T18:08 May-28 Mon Duration = 32 min; egress = T18:41 S30 45 Ring CRX Ascending T18:33 May-28 Mon r = Rs S TI (t) [T31] TITAN T18:51 May-28 Mon Outbound 2426 km flyby, v = 6.1 km/s, phase = 114 deg S30 45 XDISC Segment T21:21 May-29 Tue XDISC segment begins. Duration = 10 d S30 45 OTM TI T18:41 May-31 Thu D/L start, burn ~6h later. Backup D/L 146T09:57 S30 46 Apoapse T01:20 Jun-04 Mon Per = 16.0 d, inc = 18.0 deg, r = 37.8 Rs, phase = 57 deg Page 12

28 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S30 46 OTM-114 ~APO T10:55 Jun-05 Tue D/L start, burn ~6h later. Backup D/L 152T18:41 S30 46 SATURN Segment T03:10 Jun-09 Sat SATURN segment begins. Duration = 2 d S30 46 OTM TI T18:10 Jun-10 Sun D/L start, burn ~6h later. Backup D/L 157T18:25 S31 46 RINGS Segment T03:10 Jun-11 Mon RINGS segment begins. Duration = 2 d S31 46 S31 Begins T03:10 Jun-11 Mon S31 Sequence. Duration = 33 d S31 46 Earth OCC RING T19:36 Jun-11 Mon Duration = 208 min; egress = T23:04 S31 46 Sun OCC RING T20:16 Jun-11 Mon Duration = 176 min; egress = T23:12 S31 46 Earth OCC SATURN T20:56 Jun-11 Mon Duration = 122 min; egress = T22:58 S31 46 Sun OCC SATURN T21:18 Jun-11 Mon Duration = 118 min; egress = T23:16 S MI (nt) MIMAS T23:07 Jun-11 Mon Inbound km flyby, v = 16.3 km/s, phase = 96 deg S _Rs Dust Hazard T23:36 Jun-11 Mon End 162T23:40(00:03) HGA to RAM & MEA cover closed S31 46 Ring CRX Descending T23:38 Jun-11 Mon r = 2.90 Rs S AT (nt) ATLAS T00:16 Jun-12 Tue Inbound km flyby, v = 7.2 km/s, phase = 128 deg S PM (nt) PROMETHEUS T00:21 Jun-12 Tue Inbound km flyby, v = 11.3 km/s, phase = 82 deg S31 46 Periapse T00:51 Jun-12 Tue Per = 16.3 d, inc = 18.4 deg, r = 2.7 Rs, phase = 123 deg S EP (nt) EPIMETHEUS T01:15 Jun-12 Tue Outbound km flyby, v = 11.5 km/s, phase = 144 deg S ME (nt) METHONE T02:40 Jun-12 Tue Outbound km flyby, v = 9.2 km/s, phase = 101 deg S31 46 TOST Segment T02:54 Jun-13 Wed TOST segment begins. Duration = 2 d S31 46 Earth OCC TITAN T17:02 Jun-13 Wed Duration = 40 min; egress = T17:42 S31 46 Sun OCC TITAN T17:03 Jun-13 Wed Duration = 38 min; egress = T17:41 S31 46 Ring CRX Ascending T17:43 Jun-13 Wed r = Rs S TI (t) [T32] TITAN T17:47 Jun-13 Wed Outbound 950 km flyby, v = 6.3 km/s, phase = 107 deg S31 46 XDISC Segment T20:47 Jun-14 Thu XDISC segment begins. Duration = 12 d S31 46 OTM TI T17:39 Jun-16 Sat D/L start, burn ~6h later. Backup D/L 162T09:10 S31 47 Apoapse T01:17 Jun-20 Wed Per = 16.0 d, inc = 2.0 deg, r = 38.1 Rs, phase = 54 deg S31 47 OTM-117 ~APO T17:23 Jun-21 Thu D/L start, burn ~6h later. Backup D/L 168T17:39 S31 47 OTM TI T17:08 Jun-26 Tue D/L start, burn ~6h later. Backup D/L 173T17:23 S31 47 SOST Segment T02:08 Jun-27 Wed SOST segment begins. Duration = 2 d S TE (nt) TETHYS T19:51 Jun-27 Wed Inbound km flyby, v = 10.2 km/s, phase = 95 deg S31 47 Earth OCC SATURN T22:16 Jun-27 Wed Duration = 80 min; egress = T23:36 S31 47 Sun OCC SATURN T22:22 Jun-27 Wed Duration = 90 min; egress = T23:52 S ME (nt) METHONE T22:33 Jun-27 Wed Inbound km flyby, v = 10.3 km/s, phase = 115 deg S31 47 E_ring_lg Dust Crxing T22:45 Jun-27 Wed End 178T23:02(00:16) No protection yet identified S MI (nt) MIMAS T22:54 Jun-27 Wed Inbound km flyby, v = 16.3 km/s, phase = 110 deg S31 47 JE_inward Dust Hazard T23:57 Jun-27 Wed End 179T00:11(00:14) MEA cover closed S31 47 Ring CRX Descending T00:12 Jun-28 Thu r = 2.54 Rs S31 47 Dione Dust Hazard T00:13 Jun-28 Thu End 179T00:28(00:14) HGA to RAM & MEA cover closed S31 47 Periapse T01:02 Jun-28 Thu Per = 16.5 d, inc = 2.2 deg, r = 2.4 Rs, phase = 126 deg S EN (nt) ENCELADUS T01:10 Jun-28 Thu Outbound km flyby, v = 9.4 km/s, phase = 55 deg S PM (nt) PROMETHEUS T01:57 Jun-28 Thu Outbound km flyby, v = 10.3 km/s, phase = 154 deg S EP (nt) EPIMETHEUS T02:18 Jun-28 Thu Outbound km flyby, v = 16.7 km/s, phase = 152 deg S RH (nt) RHEA T12:06 Jun-28 Thu Outbound km flyby, v = 10.7 km/s, phase = 105 deg S31 47 TOST Segment T02:05 Jun-29 Fri TOST segment begins. Duration = 2 d S TI (t) [T33] TITAN T17:03 Jun-29 Fri Outbound 1944 km flyby, v = 6.2 km/s, phase = 96 deg S31 47 XDISC Segment T02:35 Jul-01 Sun XDISC segment begins. Duration = 17 d S31 47 Ring CRX Ascending T17:07 Jul-02 Mon r = Rs S31 47 OTM TI T16:37 Jul-03 Tue D/L start, burn ~6h later. Backup D/L 178T08:10 S31 47 OTM-120 ~APO T16:22 Jul-08 Sun D/L start, burn ~6h later. Backup D/L 185T09:07 S31 48 Apoapse T09:52 Jul-09 Mon Per = 22.8 d, inc = 0.4 deg, r = 47.8 Rs, phase = 64 deg S32 48 S32 Begins T01:06 Jul-14 Sat S32 Sequence. Duration = 29 d S32 48 OTM TI T16:06 Jul-15 Sun D/L start, burn ~6h later. Backup D/L 190T08:52 S32 48 TOST Segment T00:51 Jul-18 Wed TOST segment begins. Duration = 2 d S TI (t) [T34] TITAN T00:38 Jul-19 Thu Inbound 1300 km flyby, v = 6.2 km/s, phase = 34 deg S32 48 SATURN Segment T00:36 Jul-20 Fri SATURN segment begins. Duration = 2 d S32 48 Dione Dust Hazard T14:00 Jul-20 Fri End 201T14:30(00:29) MEA cover closed S32 48 Ring CRX Descending T14:33 Jul-20 Fri r = 6.17 Rs S HE (nt) HELENE T15:29 Jul-20 Fri Inbound km flyby, v = 4.9 km/s, phase = 58 deg S TE (nt) TETHYS T17:22 Jul-20 Fri Inbound km flyby, v = 7.6 km/s, phase = 94 deg S32 48 Periapse T19:51 Jul-20 Fri Per = 39.9 d, inc = 0.3 deg, r = 5.3 Rs, phase = 131 deg S32 48 OTM TI T15:36 Jul-21 Sat D/L start, burn ~6h later. Backup D/L 197T15:51 S32 48 XDISC Segment T00:36 Jul-22 Sun XDISC segment begins. Duration = 37 d S32 48 Ring CRX Ascending T04:41 Jul-23 Mon r = Rs S32 48 OTM-123 ~APO T14:35 Aug-05 Sun D/L start, burn ~6h later. Backup D/L 203T15:36 S32 49 Apoapse T16:31 Aug-09 Thu Per = 39.7 d, inc = 0.3 deg, r = 69.1 Rs, phase = 49 deg S33 49 S33 Begins T23:20 Aug-11 Sat S33 Sequence. Duration = 42 d S33 49 SEP = 3.0 [deg] Conjunction T13:46 Aug-18 Sat Commanding must not be required below 3.0 deg S33 49 SEP = 2.0 [deg] Conjunction T23:19 Aug-19 Sun Plan no SSR playback below 2.0 deg Page 13

29 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S33 49 SEP = 2.0 [deg] Conjunction T17:59 Aug-23 Thu Plan no SSR playback below 2.0 deg S33 49 SEP = 3.0 [deg] Conjunction T03:40 Aug-25 Sat Commanding must not be required below 3.0 deg S33 49 OTM TI T13:20 Aug-27 Mon D/L start, burn ~6h later. Backup D/L 218T14:35 S33 49 SOST Segment T22:20 Aug-27 Mon SOST segment begins. Duration = 3 d S33 49 E_ring_lg Dust Hazard T07:19 Aug-29 Wed End 241T07:48(00:29) MEA cover closed S33 49 Ring CRX Descending T07:42 Aug-29 Wed r = 6.21 Rs S TE (nt) TETHYS T11:23 Aug-29 Wed Inbound km flyby, v = 4.6 km/s, phase = 105 deg S33 49 Periapse T13:10 Aug-29 Wed Per = 39.9 d, inc = 0.3 deg, r = 5.3 Rs, phase = 132 deg S RH (nt) RHEA T01:28 Aug-30 Thu Outbound 5126 km flyby, v = 6.7 km/s, phase = 46 deg S33 49 TOST Segment T17:34 Aug-30 Thu TOST segment begins. Duration = 2 d S TI (t) [T35] TITAN T06:35 Aug-31 Fri Outbound 3212 km flyby, v = 6.1 km/s, phase = 87 deg S33 49 XDISC Segment T16:20 Sep-01 Sat XDISC segment begins. Duration = 7 d S33 49 OTM TI T05:35 Sep-02 Sun D/L start, burn ~6h later. Backup D/L 240T13:20 S33 49 OTM IA T12:50 Sep-05 Wed D/L start, burn ~6h later. Backup D/L 246T13:05 S33 49 OTM IA T12:50 Sep-08 Sat D/L start, burn ~6h later. Backup D/L 249T05:20 S33 49 SOST Segment T21:50 Sep-08 Sat SOST segment begins. Duration = 4 d S IA (t) [I1] IAPETUS T12:34 Sep-10 Mon Outbound 1229 km flyby, v = 2.4 km/s, phase = 65 deg S33 49 XDISC Segment T21:35 Sep-12 Wed XDISC segment begins. Duration = 16 d S33 49 OTM IA T12:20 Sep-13 Thu D/L start, burn ~6h later. Backup D/L 252T12:45 S33 50 Apoapse T11:46 Sep-14 Fri Per = 32.0 d, inc = 6.2 deg, r = 59.8 Rs, phase = 42 deg S33 50 OTM IA T12:21 Sep-17 Mon D/L start, burn ~6h later. Backup D/L 257T12:21 S34 50 S34 Begins T20:51 Sep-22 Sat S34 Sequence. Duration = 39 d S34 50 OTM TI T11:36 Sep-28 Fri D/L start, burn ~6h later. Backup D/L 261T04:51 S34 50 SOST Segment T20:36 Sep-28 Fri SOST segment begins. Duration = 2 d S34 50 Ring CRX Ascending T06:38 Sep-30 Sun r = 5.66 Rs S DI (nt) DIONE T06:46 Sep-30 Sun Inbound km flyby, v = 5.5 km/s, phase = 46 deg S34 50 Earth OCC SATURN T07:36 Sep-30 Sun Duration = 100 min; egress = T09:16 S34 50 Sun OCC SATURN T07:41 Sep-30 Sun Duration = 60 min; egress = T08:41 S TE (nt) TETHYS T07:56 Sep-30 Sun Inbound km flyby, v = 9.9 km/s, phase = 112 deg S EN (nt) ENCELADUS T10:59 Sep-30 Sun Inbound km flyby, v = 5.9 km/s, phase = 100 deg S34 50 Periapse T11:49 Sep-30 Sun Per = 32.2 d, inc = 6.2 deg, r = 4.6 Rs, phase = 139 deg S TL (nt) TELESTO T15:38 Sep-30 Sun Outbound km flyby, v = 8.3 km/s, phase = 164 deg S34 50 RINGS Segment T20:36 Sep-30 Sun RINGS segment begins. Duration = 1 d S34 50 TOST Segment T12:51 Oct-01 Mon TOST segment begins. Duration = 2 d S34 50 Ring CRX Descending T23:06 Oct-01 Mon r = Rs S TI (t) [T36] TITAN T04:54 Oct-02 Tue Outbound 950 km flyby, v = 6.3 km/s, phase = 67 deg S34 50 Ring CRX Ascending T15:24 Oct-02 Tue r = Rs S34 50 XDISC Segment T14:19 Oct-03 Wed XDISC segment begins. Duration = 19 d S34 50 OTM TI T11:22 Oct-05 Fri D/L start, burn ~6h later. Backup D/L 272T04:06 S34 51 Apoapse T10:12 Oct-12 Fri Per = 23.8 d, inc = 5.0 deg, r = 49.2 Rs, phase = 35 deg S HY (nt) HYPERION T15:00 Oct-21 Sun Inbound km flyby, v = 4.8 km/s, phase = 107 deg S TI (nt) TITAN T00:44 Oct-22 Mon Inbound km flyby, v = 4.1 km/s, phase = 29 deg S34 51 RINGS Segment T19:23 Oct-22 Mon RINGS segment begins. Duration = 3 d S HE (nt) HELENE T01:02 Oct-24 Wed Inbound km flyby, v = 7.3 km/s, phase = 52 deg S34 51 Sun OCC SATURN T05:31 Oct-24 Wed Duration = 74 min; egress = T06:46 S34 51 Earth OCC SATURN T05:40 Oct-24 Wed Duration = 94 min; egress = T07:14 S34 51 E_ring_lg Dust Hazard T05:51 Oct-24 Wed End 297T05:59(00:08) MEA cover closed S34 51 Ring CRX Descending T05:55 Oct-24 Wed r = 4.11 Rs S PM (nt) PROMETHEUS T06:18 Oct-24 Wed Inbound km flyby, v = 1.5 km/s, phase = 159 deg S PL (nt) PALLENE T06:34 Oct-24 Wed Inbound km flyby, v = 10.7 km/s, phase = 110 deg S34 51 Periapse T08:18 Oct-24 Wed Per = 24.3 d, inc = 5.0 deg, r = 3.7 Rs, phase = 145 deg S34 51 XDISC Segment T19:09 Oct-25 Thu XDISC segment begins. Duration = 20 d S34 51 Ring CRX Ascending T10:35 Oct-26 Fri r = Rs S35 51 S35 Begins T18:40 Oct-31 Wed S35 Sequence. Duration = 44 d S35 51 OTM-132 ~APO T09:40 Nov-01 Thu D/L start, burn ~6h later. Backup D/L 279T11:07 S35 52 Apoapse T08:14 Nov-05 Mon Per = 24.0 d, inc = 4.9 deg, r = 49.5 Rs, phase = 35 deg S35 52 SOST Segment T17:56 Nov-14 Wed SOST segment begins. Duration = 2 d S35 52 OTM TI T08:56 Nov-15 Thu D/L start, burn ~6h later. Backup D/L 306T09:40 S35 52 RINGS Segment T17:41 Nov-16 Fri RINGS segment begins. Duration = 2 d S RH (nt) RHEA T19:58 Nov-16 Fri Inbound km flyby, v = 9.0 km/s, phase = 147 deg S35 52 Sun OCC SATURN T05:25 Nov-17 Sat Duration = 78 min; egress = T06:43 S EN (nt) ENCELADUS T05:27 Nov-17 Sat Inbound km flyby, v = 11.8 km/s, phase = 120 deg S35 52 Earth OCC SATURN T05:38 Nov-17 Sat Duration = 98 min; egress = T07:15 S35 52 E_ring_lg Dust Hazard T05:42 Nov-17 Sat End 321T05:50(00:08) MEA cover closed S35 52 Ring CRX Descending T05:46 Nov-17 Sat r = 4.11 Rs S PA (nt) PANDORA T06:49 Nov-17 Sat Inbound km flyby, v = 1.7 km/s, phase = 166 deg S PN (nt) PAN T07:57 Nov-17 Sat Inbound km flyby, v = 1.5 km/s, phase = 150 deg Page 14

30 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S35 52 Periapse T08:12 Nov-17 Sat Per = 24.3 d, inc = 4.9 deg, r = 3.7 Rs, phase = 146 deg S EP (nt) EPIMETHEUS T09:09 Nov-17 Sat Outbound km flyby, v = 2.1 km/s, phase = 112 deg S CA (nt) CALYPSO T12:56 Nov-17 Sat Outbound km flyby, v = 11.0 km/s, phase = 148 deg S35 52 TOST Segment T10:12 Nov-18 Sun TOST segment begins. Duration = 2 d S TI (t) [T37] TITAN T00:58 Nov-19 Mon Outbound 950 km flyby, v = 6.3 km/s, phase = 51 deg S35 52 Ring CRX Ascending T04:44 Nov-19 Mon r = Rs S35 52 XDISC Segment T09:57 Nov-20 Tue XDISC segment begins. Duration = 5 d S35 52 OTM TI T00:57 Nov-22 Thu D/L start, burn ~6h later. Backup D/L 321T08:42 S35 53 Apoapse T08:00 Nov-25 Sun Per = 16.0 d, inc = 12.3 deg, r = 38.0 Rs, phase = 25 deg S35 53 MAG Segment T17:13 Nov-25 Sun MAG segment begins. Duration = 3 d S35 53 OTM-135 ~APO T00:43 Nov-27 Tue D/L start, burn ~6h later. Backup D/L 327T08:28 S35 53 RINGS Segment T16:58 Nov-28 Wed RINGS segment begins. Duration = 4 d S35 53 OTM TI T07:44 Dec-02 Sun D/L start, burn ~6h later. Backup D/L 332T07:58 S35 53 MAG Segment T16:44 Dec-02 Sun MAG segment begins. Duration = 2 d S35 53 Sun OCC RING T05:01 Dec-03 Mon Duration = 90 min; egress = T06:31 S35 53 Earth OCC RING T05:21 Dec-03 Mon Duration = 74 min; egress = T06:36 S MI (nt) MIMAS T05:28 Dec-03 Mon Inbound km flyby, v = 14.8 km/s, phase = 138 deg S TL (nt) TELESTO T05:34 Dec-03 Mon Inbound km flyby, v = 9.1 km/s, phase = 19 deg S35 53 Sun OCC SATURN T06:14 Dec-03 Mon Duration = 83 min; egress = T07:37 S35 53 Earth OCC SATURN T06:25 Dec-03 Mon Duration = 86 min; egress = T07:51 S35 53 E_ring_lg Dust Crxing T06:43 Dec-03 Mon End 337T06:49(00:05) No protection yet identified S35 53 Ring CRX Descending T06:46 Dec-03 Mon r = 2.65 Rs S EP (nt) EPIMETHEUS T06:58 Dec-03 Mon Inbound 6364 km flyby, v = 7.5 km/s, phase = 139 deg S35 53 Periapse T07:43 Dec-03 Mon Per = 16.5 d, inc = 12.7 deg, r = 2.5 Rs, phase = 155 deg S35 53 TOST Segment T09:14 Dec-04 Tue TOST segment begins. Duration = 2 d S TI (t) [T38] TITAN T00:06 Dec-05 Wed Outbound 1300 km flyby, v = 6.3 km/s, phase = 70 deg S35 53 Ring CRX Ascending T02:16 Dec-05 Wed r = Rs S35 53 RINGS Segment T09:29 Dec-06 Thu RINGS segment begins. Duration = 2 d S35 53 OTM TI T00:00 Dec-08 Sat D/L start, burn ~6h later. Backup D/L 337T09:10 S35 53 MAG Segment T09:00 Dec-08 Sat MAG segment begins. Duration = 6 d S35 54 Apoapse T05:33 Dec-11 Tue Per = 15.9 d, inc = 26.3 deg, r = 37.5 Rs, phase = 30 deg S35 54 OTM-138 ~APO T01:10 Dec-13 Thu D/L start, burn ~6h later. Backup D/L 343T07:30 S36 54 SATURN Segment T16:00 Dec-14 Fri SATURN segment begins. Duration = 6 d S36 54 S36 Begins T16:00 Dec-14 Fri S36 Sequence. Duration = 39 d S36 54 OTM TI T23:16 Dec-17 Mon D/L start, burn ~6h later. Backup D/L 348T07:00 S36 54 Sun OCC RING T02:02 Dec-19 Wed Duration = 70 min; egress = T03:12 S36 54 Earth OCC RING T02:28 Dec-19 Wed Duration = 50 min; egress = T03:18 S36 54 Sun OCC SATURN T03:05 Dec-19 Wed Duration = 75 min; egress = T04:20 S36 54 Earth OCC SATURN T03:22 Dec-19 Wed Duration = 75 min; egress = T04:37 S36 54 Ring CRX Descending T03:33 Dec-19 Wed r = 3.23 Rs S36 54 Periapse T05:01 Dec-19 Wed Per = 16.2 d, inc = 26.5 deg, r = 3.0 Rs, phase = 150 deg S36 54 TOST Segment T08:16 Dec-20 Thu TOST segment begins. Duration = 2 d S TI (t) [T39] TITAN T22:53 Dec-20 Thu Outbound 950 km flyby, v = 6.3 km/s, phase = 61 deg S36 54 Ring CRX Ascending T00:10 Dec-21 Fri r = Rs S36 54 MAG Segment T08:57 Dec-22 Sat MAG segment begins. Duration = 10 d S36 54 OTM TI T23:02 Dec-23 Sun D/L start, burn ~6h later. Backup D/L 353T06:46 S36 55 Apoapse T01:24 Dec-27 Thu Per = 15.9 d, inc = 37.9 deg, r = 36.5 Rs, phase = 37 deg S36 55 OTM-141 ~APO T06:02 Dec-29 Sat D/L start, burn ~6h later. Backup D/L 359T06:17 S36 55 SATURN Segment T15:03 Jan-01 Tue SATURN segment begins. Duration = 4 d S36 55 OTM TI T22:18 Jan-02 Wed D/L start, burn ~6h later. Backup D/L 364T06:02 S DI (nt) DIONE T20:09 Jan-03 Thu Inbound km flyby, v = 11.2 km/s, phase = 77 deg S36 55 Sun OCC RING T20:24 Jan-03 Thu Duration = 57 min; egress = T21:21 S36 55 Earth OCC RING T20:51 Jan-03 Thu Duration = 40 min; egress = T21:30 S PL (nt) PALLENE T21:49 Jan-03 Thu Inbound km flyby, v = 9.5 km/s, phase = 120 deg S36 55 E_ring_lg Dust Crxing T22:00 Jan-03 Thu End 003T22:02(00:01) No protection yet identified S36 55 Ring CRX Descending T22:01 Jan-03 Thu r = 4.36 Rs S JA (nt) JANUS T22:11 Jan-03 Thu Inbound km flyby, v = 10.1 km/s, phase = 155 deg S PM (nt) PROMETHEUS T23:11 Jan-03 Thu Inbound km flyby, v = 10.6 km/s, phase = 150 deg S PA (nt) PANDORA T00:32 Jan-04 Fri Inbound km flyby, v = 11.4 km/s, phase = 117 deg S36 55 Periapse T00:43 Jan-04 Fri Per = 16.0 d, inc = 38.0 deg, r = 4.0 Rs, phase = 143 deg S36 55 TOST Segment T05:48 Jan-05 Sat TOST segment begins. Duration = 2 d S TI (t) [T40] TITAN T21:25 Jan-05 Sat Outbound 950 km flyby, v = 6.3 km/s, phase = 37 deg S36 55 Ring CRX Ascending T22:15 Jan-05 Sat r = Rs S36 55 MAG Segment T07:26 Jan-07 Mon MAG segment begins. Duration = 6 d S36 56 Apoapse T22:29 Jan-09 Wed Per = 12.0 d, inc = 47.0 deg, r = 30.1 Rs, phase = 31 deg S36 56 RINGS Segment T14:04 Jan-13 Sun RINGS segment begins. Duration = 6 d Page 15

31 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S36 56 Sun OCC RING T19:17 Jan-15 Tue Duration = 50 min; egress = T20:06 S36 56 Earth OCC RING T19:31 Jan-15 Tue Duration = 38 min; egress = T20:09 S36 56 Sun OCC SATURN T19:51 Jan-15 Tue Duration = 59 min; egress = T20:50 S36 56 Earth OCC SATURN T20:14 Jan-15 Tue Duration = 40 min; egress = T20:54 S36 56 Ring CRX Descending T20:21 Jan-15 Tue r = 3.46 Rs S ME (nt) METHONE T20:38 Jan-15 Tue Inbound km flyby, v = 14.8 km/s, phase = 113 deg S36 56 Periapse T21:54 Jan-15 Tue Per = 12.0 d, inc = 47.0 deg, r = 3.3 Rs, phase = 149 deg S36 56 OTM TI+P T22:15 Jan-15 Tue D/L start, burn ~6h later. Backup D/L 004T07:18 S36 56 Ring CRX Ascending T20:39 Jan-17 Thu r = Rs S36 56 MAG Segment T13:49 Jan-19 Sat MAG segment begins. Duration = 5 d S36 57 Apoapse T21:12 Jan-21 Mon Per = 11.9 d, inc = 47.0 deg, r = 30.1 Rs, phase = 31 deg S37 57 S37 Begins T13:35 Jan-22 Tue S37 Sequence. Duration = 25 d S TI (nt) TITAN T21:09 Jan-22 Tue Inbound km flyby, v = 4.5 km/s, phase = 70 deg S37 57 RINGS Segment T13:20 Jan-24 Thu RINGS segment begins. Duration = 7 d S TI (nt) TITAN T12:13 Jan-27 Sun Inbound km flyby, v = 9.4 km/s, phase = 61 deg S37 57 Sun OCC RING T17:51 Jan-27 Sun Duration = 48 min; egress = T18:40 S37 57 Earth OCC RING T18:02 Jan-27 Sun Duration = 40 min; egress = T18:42 S37 57 Sun OCC SATURN T18:28 Jan-27 Sun Duration = 56 min; egress = T19:24 S37 57 Earth OCC SATURN T18:45 Jan-27 Sun Duration = 41 min; egress = T19:26 S37 57 Ring CRX Descending T18:54 Jan-27 Sun r = 3.47 Rs S AT (nt) ATLAS T19:11 Jan-27 Sun Inbound km flyby, v = 13.9 km/s, phase = 155 deg S EP (nt) EPIMETHEUS T20:07 Jan-27 Sun Inbound km flyby, v = 17.1 km/s, phase = 112 deg S PM (nt) PROMETHEUS T20:10 Jan-27 Sun Inbound km flyby, v = 16.1 km/s, phase = 117 deg S37 57 Periapse T20:28 Jan-27 Sun Per = 12.0 d, inc = 47.0 deg, r = 3.3 Rs, phase = 149 deg S37 57 Ring CRX Ascending T18:57 Jan-29 Tue r = Rs S37 57 MAG Segment T12:50 Jan-31 Thu MAG segment begins. Duration = 6 d S37 58 Apoapse T20:00 Feb-02 Sat Per = 12.0 d, inc = 47.0 deg, r = 30.2 Rs, phase = 31 deg S37 58 OTM-144 ~APO T20:06 Feb-05 Tue D/L start, burn ~6h later. Backup D/L 016T21:19 S37 58 SATURN Segment T05:06 Feb-06 Wed SATURN segment begins. Duration = 6 d S37 58 Sun OCC RING T16:48 Feb-08 Fri Duration = 47 min; egress = T17:36 S37 58 Earth OCC RING T16:54 Feb-08 Fri Duration = 42 min; egress = T17:37 S EP (nt) EPIMETHEUS T17:00 Feb-08 Fri Inbound km flyby, v = 13.5 km/s, phase = 121 deg S37 58 Sun OCC SATURN T17:19 Feb-08 Fri Duration = 61 min; egress = T18:20 S37 58 Earth OCC SATURN T17:29 Feb-08 Fri Duration = 52 min; egress = T18:22 S37 58 Ring CRX Descending T17:50 Feb-08 Fri r = 3.45 Rs S PA (nt) PANDORA T19:20 Feb-08 Fri Inbound km flyby, v = 17.6 km/s, phase = 109 deg S37 58 Periapse T19:21 Feb-08 Fri Per = 12.1 d, inc = 47.6 deg, r = 3.3 Rs, phase = 149 deg S AT (nt) ATLAS T19:24 Feb-08 Fri Outbound km flyby, v = 17.5 km/s, phase = 109 deg S37 58 Ring CRX Ascending T18:54 Feb-10 Sun r = Rs S37 58 MAG Segment T12:06 Feb-12 Tue MAG segment begins. Duration = 6 d S37 59 Apoapse T19:27 Feb-14 Thu Per = 12.0 d, inc = 47.6 deg, r = 30.3 Rs, phase = 31 deg S38 59 S38 Begins T11:51 Feb-16 Sat S38 Sequence. Duration = 36 d S38 59 SATURN Segment T11:36 Feb-18 Mon SATURN segment begins. Duration = 4 d S38 59 OTM TI T02:36 Feb-19 Tue D/L start, burn ~6h later. Backup D/L 038T03:36 S38 59 Sun OCC RING T17:03 Feb-20 Wed Duration = 46 min; egress = T17:49 S38 59 Earth OCC RING T17:03 Feb-20 Wed Duration = 46 min; egress = T17:49 S38 59 Sun OCC SATURN T17:36 Feb-20 Wed Duration = 58 min; egress = T18:33 S38 59 Earth OCC SATURN T17:38 Feb-20 Wed Duration = 54 min; egress = T18:33 S PN (nt) PAN T17:53 Feb-20 Wed Inbound km flyby, v = 13.9 km/s, phase = 148 deg S38 59 Ring CRX Descending T18:02 Feb-20 Wed r = 3.45 Rs S PM (nt) PROMETHEUS T18:22 Feb-20 Wed Inbound km flyby, v = 14.1 km/s, phase = 155 deg S PA (nt) PANDORA T18:32 Feb-20 Wed Inbound km flyby, v = 14.4 km/s, phase = 151 deg S JA (nt) JANUS T19:13 Feb-20 Wed Inbound km flyby, v = 17.0 km/s, phase = 113 deg S38 59 Periapse T19:34 Feb-20 Wed Per = 12.1 d, inc = 47.6 deg, r = 3.3 Rs, phase = 149 deg S38 59 TOST Segment T03:51 Feb-22 Fri TOST segment begins. Duration = 2 d S TI (t) [T41] TITAN T17:39 Feb-22 Fri Outbound 950 km flyby, v = 6.4 km/s, phase = 30 deg S38 59 Ring CRX Ascending T18:29 Feb-22 Fri r = Rs S38 59 SATURN Segment T11:21 Feb-24 Sun SATURN segment begins. Duration = 4 d S38 60 Apoapse T22:10 Feb-25 Mon Per = 10.6 d, inc = 56.7 deg, r = 27.1 Rs, phase = 31 deg S38 60 RINGS Segment T10:51 Feb-28 Thu RINGS segment begins. Duration = 2 d S38 60 MAG Segment T10:51 Mar-01 Sat MAG segment begins. Duration = 5 d S38 60 OTM TI+P T16:56 Mar-01 Sat D/L start, burn ~6h later. Backup D/L 052T02:36 S38 60 Earth OCC RING T02:14 Mar-02 Sun Duration = 46 min; egress = T03:00 S38 60 Sun OCC RING T02:19 Mar-02 Sun Duration = 42 min; egress = T03:01 S38 60 Earth OCC SATURN T03:02 Mar-02 Sun Duration = 20 min; egress = T03:22 S38 60 Sun OCC SATURN T03:12 Mar-02 Sun Duration = 7 min; egress = T03:19 Page 16

32 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S38 60 E_ring_lg Dust Hazard T03:19 Mar-02 Sun End 062T03:20(00:00) MEA cover closed S38 60 Ring CRX Descending T03:19 Mar-02 Sun r = 3.94 Rs S PM (nt) PROMETHEUS T04:17 Mar-02 Sun Inbound km flyby, v = 16.3 km/s, phase = 143 deg S38 60 Periapse T05:10 Mar-02 Sun Per = 10.7 d, inc = 56.7 deg, r = 3.7 Rs, phase = 149 deg S38 60 Ring CRX Ascending T08:37 Mar-04 Tue r = Rs S38 60 RINGS Segment T10:21 Mar-06 Thu RINGS segment begins. Duration = 6 d S38 60 OTM-147 ~APO T01:21 Mar-07 Fri D/L start, burn ~6h later. Backup D/L 063T01:36 S38 61 Apoapse T13:04 Mar-07 Fri Per = 10.7 d, inc = 56.7 deg, r = 27.2 Rs, phase = 31 deg S38 61 OTM EN T01:06 Mar-10 Mon D/L start, burn ~6h later. Backup D/L 068T01:21 S TI (nt) TITAN T19:24 Mar-10 Mon Inbound km flyby, v = 6.3 km/s, phase = 124 deg S38 61 SOST Segment T02:36 Mar-12 Wed SOST segment begins. Duration = 1 d S38 61 Earth OCC RING T17:58 Mar-12 Wed Duration = 48 min; egress = T18:46 S38 61 Sun OCC RING T18:07 Mar-12 Wed Duration = 41 min; egress = T18:48 S38 61 Earth OCC SATURN T18:42 Mar-12 Wed Duration = 30 min; egress = T19:11 S38 61 E_ring_lg Dust Hazard T19:06 Mar-12 Wed End 072T19:07(00:00) MEA cover closed S38 61 Ring CRX Descending T19:07 Mar-12 Wed r = 3.95 Rs S EN (t) [E3] ENCELADUS T19:07 Mar-12 Wed Inbound 97 km flyby, v = 14.5 km/s, phase = 100 deg S38 61 Periapse T20:57 Mar-12 Wed Per = 10.7 d, inc = 56.7 deg, r = 3.7 Rs, phase = 149 deg S38 61 RINGS Segment T09:51 Mar-13 Thu RINGS segment begins. Duration = 12 d S38 61 OTM EN T17:21 Mar-13 Thu D/L start, burn ~6h later. Backup D/L 071T01:06 S38 61 Ring CRX Ascending T00:14 Mar-15 Sat r = Rs S38 61 OTM-150 ~APO T00:35 Mar-18 Tue D/L start, burn ~6h later. Backup D/L 075T00:51 S38 62 Apoapse T04:38 Mar-18 Tue Per = 10.6 d, inc = 56.7 deg, r = 27.2 Rs, phase = 31 deg S38 62 OTM TI T16:50 Mar-22 Sat D/L start, burn ~6h later. Backup D/L 079T00:35 S39 62 S39 Begins T01:50 Mar-23 Sun S39 Sequence. Duration = 27 d S39 62 Earth OCC RING T09:17 Mar-23 Sun Duration = 50 min; egress = T10:07 S39 62 Sun OCC RING T09:31 Mar-23 Sun Duration = 40 min; egress = T10:11 S39 62 Earth OCC SATURN T09:58 Mar-23 Sun Duration = 36 min; egress = T10:34 S _Rs Dust Hazard T10:28 Mar-23 Sun End 083T10:29(00:00) MEA cover closed S39 62 Ring CRX Descending T10:29 Mar-23 Sun r = 3.94 Rs S PL (nt) PALLENE T10:42 Mar-23 Sun Inbound km flyby, v = 15.0 km/s, phase = 142 deg S EP (nt) EPIMETHEUS T10:57 Mar-23 Sun Inbound km flyby, v = 15.6 km/s, phase = 155 deg S ME (nt) METHONE T11:29 Mar-23 Sun Inbound km flyby, v = 16.9 km/s, phase = 115 deg S39 62 Periapse T12:19 Mar-23 Sun Per = 10.7 d, inc = 56.7 deg, r = 3.7 Rs, phase = 149 deg S39 62 TOST Segment T01:35 Mar-25 Tue TOST segment begins. Duration = 2 d S TI (t) [T42] TITAN T14:35 Mar-25 Tue Outbound 950 km flyby, v = 6.4 km/s, phase = 21 deg S39 62 Ring CRX Ascending T15:16 Mar-25 Tue r = Rs S39 62 SATURN Segment T01:20 Mar-27 Thu SATURN segment begins. Duration = 4 d S39 63 Apoapse T01:28 Mar-28 Fri Per = 9.6 d, inc = 63.6 deg, r = 24.5 Rs, phase = 31 deg S39 63 RINGS Segment T08:34 Mar-31 Mon RINGS segment begins. Duration = 13 d S TI (nt) TITAN T16:01 Apr-01 Tue Inbound km flyby, v = 12.9 km/s, phase = 36 deg S39 63 Earth OCC RING T16:55 Apr-01 Tue Duration = 51 min; egress = T17:46 S39 63 Sun OCC RING T17:14 Apr-01 Tue Duration = 38 min; egress = T17:52 S PL (nt) PALLENE T17:23 Apr-01 Tue Inbound km flyby, v = 14.9 km/s, phase = 122 deg S39 63 Ring CRX Descending T18:16 Apr-01 Tue r = 4.51 Rs S JA (nt) JANUS T19:11 Apr-01 Tue Inbound km flyby, v = 16.7 km/s, phase = 150 deg S39 63 Periapse T20:24 Apr-01 Tue Per = 9.6 d, inc = 63.7 deg, r = 4.3 Rs, phase = 149 deg S39 63 Ring CRX Ascending T05:08 Apr-04 Fri r = Rs S39 64 Apoapse T15:25 Apr-06 Sun Per = 9.6 d, inc = 63.6 deg, r = 24.5 Rs, phase = 31 deg S39 64 OTM TI+P T19:04 Apr-10 Thu D/L start, burn ~6h later. Backup D/L 084T00:20 S39 64 Earth OCC RING T06:53 Apr-11 Fri Duration = 52 min; egress = T07:46 S39 64 Sun OCC RING T07:15 Apr-11 Fri Duration = 37 min; egress = T07:52 S39 64 Ring CRX Descending T08:16 Apr-11 Fri r = 4.51 Rs S MI (nt) MIMAS T09:33 Apr-11 Fri Inbound km flyby, v = 17.0 km/s, phase = 133 deg S39 64 Periapse T10:25 Apr-11 Fri Per = 9.6 d, inc = 63.6 deg, r = 4.3 Rs, phase = 149 deg S39 64 SATURN Segment T07:48 Apr-13 Sun SATURN segment begins. Duration = 6 d S39 64 Ring CRX Ascending T19:00 Apr-13 Sun r = Rs S39 65 Apoapse T05:06 Apr-16 Wed Per = 9.6 d, inc = 63.6 deg, r = 24.5 Rs, phase = 31 deg S40 65 RINGS Segment T07:18 Apr-19 Sat RINGS segment begins. Duration = 14 d S40 65 S40 Begins T07:18 Apr-19 Sat S40 Sequence. Duration = 42 d S40 65 Earth OCC RING T20:15 Apr-20 Sun Duration = 54 min; egress = T21:08 S40 65 Sun OCC RING T20:39 Apr-20 Sun Duration = 36 min; egress = T21:15 S MI (nt) MIMAS T20:46 Apr-20 Sun Inbound km flyby, v = 15.7 km/s, phase = 134 deg S40 65 Ring CRX Descending T21:38 Apr-20 Sun r = 4.50 Rs S TL (nt) TELESTO T21:54 Apr-20 Sun Inbound km flyby, v = 15.5 km/s, phase = 87 deg Page 17

33 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S EP (nt) EPIMETHEUS T22:35 Apr-20 Sun Inbound km flyby, v = 16.8 km/s, phase = 150 deg S40 65 Periapse T23:47 Apr-20 Sun Per = 9.6 d, inc = 63.6 deg, r = 4.3 Rs, phase = 149 deg S40 65 Ring CRX Ascending T08:17 Apr-23 Wed r = Rs S40 66 Apoapse T18:22 Apr-25 Fri Per = 9.6 d, inc = 63.6 deg, r = 24.5 Rs, phase = 30 deg S40 66 OTM-153 ~APO T21:47 Apr-25 Fri D/L start, burn ~6h later. Backup D/L 102T22:48 S TI (nt) TITAN T18:28 Apr-26 Sat Inbound km flyby, v = 5.5 km/s, phase = 94 deg S40 66 Earth OCC RING T09:23 Apr-30 Wed Duration = 54 min; egress = T10:17 S40 66 Sun OCC RING T09:50 Apr-30 Wed Duration = 35 min; egress = T10:25 S TL (nt) TELESTO T10:29 Apr-30 Wed Inbound km flyby, v = 14.5 km/s, phase = 48 deg S40 66 Ring CRX Descending T10:48 Apr-30 Wed r = 4.50 Rs S PL (nt) PALLENE T11:53 Apr-30 Wed Inbound km flyby, v = 16.4 km/s, phase = 124 deg S40 66 Periapse T12:56 Apr-30 Wed Per = 9.6 d, inc = 63.6 deg, r = 4.3 Rs, phase = 150 deg S40 66 Ring CRX Ascending T21:26 May-02 Fri r = Rs S40 66 SATURN Segment T06:16 May-03 Sat SATURN segment begins. Duration = 6 d S40 67 Apoapse T07:35 May-05 Mon Per = 9.6 d, inc = 63.6 deg, r = 24.5 Rs, phase = 30 deg S40 67 OTM TI T21:00 May-08 Thu D/L start, burn ~6h later. Backup D/L 117T21:47 S40 67 RINGS Segment T06:00 May-09 Fri RINGS segment begins. Duration = 3 d S40 67 Earth OCC RING T22:42 May-09 Fri Duration = 53 min; egress = T23:35 S40 67 Sun OCC RING T23:10 May-09 Fri Duration = 34 min; egress = T23:44 S ME (nt) METHONE T23:35 May-09 Fri Inbound km flyby, v = 15.3 km/s, phase = 138 deg S40 67 Ring CRX Descending T00:06 May-10 Sat r = 4.50 Rs S JA (nt) JANUS T00:06 May-10 Sat Inbound km flyby, v = 16.4 km/s, phase = 157 deg S40 67 Periapse T02:14 May-10 Sat Per = 9.6 d, inc = 63.6 deg, r = 4.3 Rs, phase = 150 deg S40 67 TOST Segment T22:30 May-11 Sun TOST segment begins. Duration = 2 d S TI (t) [T43] TITAN T10:10 May-12 Mon Outbound 950 km flyby, v = 6.4 km/s, phase = 35 deg S40 67 Ring CRX Ascending T10:39 May-12 Mon r = Rs S40 67 RINGS Segment T22:14 May-13 Tue RINGS segment begins. Duration = 3 d S40 68 Apoapse T00:10 May-14 Wed Per = 8.0 d, inc = 70.0 deg, r = 22.2 Rs, phase = 24 deg S40 68 OTM TI+P T19:20 May-16 Fri D/L start, burn ~6h later. Backup D/L 130T12:00 S40 68 SATURN Segment T04:20 May-17 Sat SATURN segment begins. Duration = 10 d S40 68 Earth OCC SATURN T21:56 May-17 Sat Duration = 72 min; egress = T23:08 S40 68 Earth OCC RING T21:57 May-17 Sat Duration = 45 min; egress = T22:43 S40 68 Sun OCC RING T22:15 May-17 Sat Duration = 30 min; egress = T22:46 S40 68 Sun OCC SATURN T22:34 May-17 Sat Duration = 28 min; egress = T23:01 S40 68 Ring CRX Descending T22:53 May-17 Sat r = 3.32 Rs S CA (nt) CALYPSO T22:55 May-17 Sat Inbound km flyby, v = 18.4 km/s, phase = 56 deg S ME (nt) METHONE T23:30 May-17 Sat Inbound km flyby, v = 20.3 km/s, phase = 106 deg S40 68 Periapse T23:46 May-17 Sat Per = 8.0 d, inc = 70.0 deg, r = 3.3 Rs, phase = 156 deg S EP (nt) EPIMETHEUS T00:02 May-18 Sun Outbound km flyby, v = 21.7 km/s, phase = 117 deg S40 68 Ring CRX Ascending T09:52 May-20 Tue r = Rs S40 68 OTM-156 ~APO T20:13 May-21 Wed D/L start, burn ~6h later. Backup D/L 139T13:44 S40 69 Apoapse T23:21 May-21 Wed Per = 8.0 d, inc = 70.0 deg, r = 22.2 Rs, phase = 24 deg S40 69 OTM TI T11:28 May-25 Sun D/L start, burn ~6h later. Backup D/L 143T19:58 S40 69 Earth OCC SATURN T21:09 May-25 Sun Duration = 70 min; egress = T22:19 S40 69 Earth OCC RING T21:09 May-25 Sun Duration = 44 min; egress = T21:54 S40 69 Sun OCC RING T21:27 May-25 Sun Duration = 30 min; egress = T21:57 S40 69 Sun OCC SATURN T21:49 May-25 Sun Duration = 20 min; egress = T22:09 S PL (nt) PALLENE T21:57 May-25 Sun Inbound km flyby, v = 18.4 km/s, phase = 44 deg S40 69 Ring CRX Descending T22:04 May-25 Sun r = 3.32 Rs S AT (nt) ATLAS T22:11 May-25 Sun Inbound km flyby, v = 20.0 km/s, phase = 158 deg S JA (nt) JANUS T22:45 May-25 Sun Inbound km flyby, v = 20.7 km/s, phase = 130 deg S40 69 Periapse T22:57 May-25 Sun Per = 8.0 d, inc = 70.0 deg, r = 3.3 Rs, phase = 156 deg S40 69 TOST Segment T04:43 May-27 Tue TOST segment begins. Duration = 3 d S TI (t) [T44] TITAN T08:33 May-28 Wed Outbound 1348 km flyby, v = 6.3 km/s, phase = 23 deg S40 69 Ring CRX Ascending T09:05 May-28 Wed r = Rs S40 70 Apoapse T09:02 May-29 Thu Per = 7.1 d, inc = 75.4 deg, r = 20.9 Rs, phase = 22 deg S40 70 RINGS Segment T21:12 May-29 Thu RINGS segment begins. Duration = 2 d S41 70 S41 Begins T04:27 May-31 Sat S41 Sequence. Duration = 31 d S41 70 MAG Segment T03:27 Jun-01 Sun MAG segment begins. Duration = 3 d S41 70 Earth OCC SATURN T21:04 Jun-01 Sun Duration = 75 min; egress = T22:19 S41 70 Earth OCC RING T21:16 Jun-01 Sun Duration = 39 min; egress = T21:54 S41 70 Sun OCC SATURN T21:24 Jun-01 Sun Duration = 54 min; egress = T22:18 S41 70 Sun OCC RING T21:29 Jun-01 Sun Duration = 26 min; egress = T21:55 S PL (nt) PALLENE T21:36 Jun-01 Sun Inbound km flyby, v = 21.3 km/s, phase = 59 deg S JA (nt) JANUS T21:56 Jun-01 Sun Inbound km flyby, v = 22.4 km/s, phase = 148 deg Page 18

34 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment S _Rs Dust Hazard T21:57 Jun-01 Sun End 153T21:58(00:01) MEA cover closed S41 70 Ring CRX Descending T21:58 Jun-01 Sun r = 2.72 Rs S41 70 Periapse T22:22 Jun-01 Sun Per = 7.2 d, inc = 75.4 deg, r = 2.7 Rs, phase = 158 deg S41 70 RINGS Segment T04:11 Jun-04 Wed RINGS segment begins. Duration = 4 d S41 70 Ring CRX Ascending T12:03 Jun-04 Wed r = Rs S41 71 Apoapse T11:46 Jun-05 Thu Per = 7.1 d, inc = 75.4 deg, r = 21.0 Rs, phase = 22 deg S41 71 MAG Segment T02:45 Jun-08 Sun MAG segment begins. Duration = 2 d S41 71 Earth OCC SATURN T23:53 Jun-08 Sun Duration = 74 min; egress = T01:06 S41 71 Earth OCC RING T00:04 Jun-09 Mon Duration = 38 min; egress = T00:42 S41 71 Sun OCC SATURN T00:13 Jun-09 Mon Duration = 53 min; egress = T01:05 S PN (nt) PAN T00:14 Jun-09 Mon Inbound km flyby, v = 23.0 km/s, phase = 112 deg S41 71 Sun OCC RING T00:17 Jun-09 Mon Duration = 26 min; egress = T00:43 S _Rs Dust Hazard T00:45 Jun-09 Mon End 161T00:46(00:01) MEA cover closed S41 71 Ring CRX Descending T00:45 Jun-09 Mon r = 2.72 Rs S41 71 Periapse T01:10 Jun-09 Mon Per = 7.2 d, inc = 75.4 deg, r = 2.7 Rs, phase = 158 deg S PA (nt) PANDORA T01:41 Jun-09 Mon Outbound km flyby, v = 25.3 km/s, phase = 113 deg S41 71 RINGS Segment T02:50 Jun-10 Tue RINGS segment begins. Duration = 5 d S41 71 Ring CRX Ascending T15:05 Jun-11 Wed r = Rs S41 72 Apoapse T14:30 Jun-12 Thu Per = 7.1 d, inc = 75.5 deg, r = 20.9 Rs, phase = 22 deg S TI (nt) TITAN T04:20 Jun-13 Fri Inbound km flyby, v = 5.9 km/s, phase = 89 deg S41 72 SATURN Segment T03:40 Jun-15 Sun SATURN segment begins. Duration = 7 d S41 72 Earth OCC SATURN T02:31 Jun-16 Mon Duration = 72 min; egress = T03:43 S41 72 Earth OCC RING T02:42 Jun-16 Mon Duration = 37 min; egress = T03:18 S41 72 Sun OCC SATURN T02:50 Jun-16 Mon Duration = 52 min; egress = T03:41 S41 72 Sun OCC RING T02:54 Jun-16 Mon Duration = 25 min; egress = T03:19 S _Rs Dust Hazard T03:21 Jun-16 Mon End 168T03:22(00:01) MEA cover closed S41 72 Ring CRX Descending T03:21 Jun-16 Mon r = 2.70 Rs S41 72 Periapse T03:45 Jun-16 Mon Per = 7.2 d, inc = 75.5 deg, r = 2.7 Rs, phase = 158 deg S EP (nt) EPIMETHEUS T04:03 Jun-16 Mon Outbound km flyby, v = 24.4 km/s, phase = 111 deg S PM (nt) PROMETHEUS T04:12 Jun-16 Mon Outbound km flyby, v = 25.0 km/s, phase = 114 deg S41 72 Ring CRX Ascending T17:49 Jun-18 Wed r = Rs S41 73 Apoapse T17:03 Jun-19 Thu Per = 7.1 d, inc = 75.5 deg, r = 21.0 Rs, phase = 22 deg S41 73 MAG Segment T03:09 Jun-22 Sun MAG segment begins. Duration = 2 d S41 73 Earth OCC SATURN T05:07 Jun-23 Mon Duration = 70 min; egress = T06:18 S EP (nt) EPIMETHEUS T05:13 Jun-23 Mon Inbound km flyby, v = 23.0 km/s, phase = 94 deg S41 73 Earth OCC RING T05:18 Jun-23 Mon Duration = 36 min; egress = T05:53 S41 73 Sun OCC SATURN T05:26 Jun-23 Mon Duration = 50 min; egress = T06:16 S AT (nt) ATLAS T05:27 Jun-23 Mon Inbound km flyby, v = 22.9 km/s, phase = 108 deg S41 73 Sun OCC RING T05:30 Jun-23 Mon Duration = 25 min; egress = T05:54 S _Rs Dust Hazard T05:56 Jun-23 Mon End 175T05:57(00:01) MEA cover closed S41 73 Ring CRX Descending T05:56 Jun-23 Mon r = 2.70 Rs S41 73 Periapse T06:20 Jun-23 Mon Per = 7.2 d, inc = 75.5 deg, r = 2.7 Rs, phase = 158 deg S41 73 SATURN Segment T03:09 Jun-24 Tue SATURN segment begins. Duration = 6 d S41 73 Ring CRX Ascending T20:38 Jun-25 Wed r = Rs S41 74 Apoapse T19:35 Jun-26 Thu Per = 7.1 d, inc = 75.5 deg, r = 20.9 Rs, phase = 22 deg S TI (nt) TITAN T15:54 Jun-28 Sat Inbound km flyby, v = 7.9 km/s, phase = 107 deg S41 74 MAG Segment T19:08 Jun-29 Sun MAG segment begins. S PN (nt) PAN T07:25 Jun-30 Mon Inbound km flyby, v = 24.0 km/s, phase = 101 deg S41 74 Earth OCC SATURN T07:39 Jun-30 Mon Duration = 68 min; egress = T08:48 S41 74 Earth OCC RING T07:49 Jun-30 Mon Duration = 34 min; egress = T08:23 S41 74 Sun OCC SATURN T07:57 Jun-30 Mon Duration = 48 min; egress = T08:45 S41 74 Sun OCC RING T08:00 Jun-30 Mon Duration = 24 min; egress = T08:24 S PM (nt) PROMETHEUS T08:06 Jun-30 Mon Inbound km flyby, v = 22.7 km/s, phase = 111 deg S41 74 Tethys Dust Crxing T08:26 Jun-30 Mon End 182T08:27(00:01) MEA cover closed S41 74 Ring CRX Descending T08:26 Jun-30 Mon r = 2.70 Rs S EN (nt) ENCELADUS T08:30 Jun-30 Mon Inbound km flyby, v = 21.4 km/s, phase = 57 deg S JA (nt) JANUS T08:46 Jun-30 Mon Inbound km flyby, v = 23.1 km/s, phase = 116 deg S41 74 Periapse T08:50 Jun-30 Mon Per = 7.2 d, inc = 75.5 deg, r = 2.7 Rs, phase = 158 deg S ME (nt) METHONE T08:50 Jun-30 Mon Outbound km flyby, v = 23.0 km/s, phase = 96 deg S AT (nt) ATLAS T09:12 Jun-30 Mon Outbound km flyby, v = 24.7 km/s, phase = 116 deg EM 74 EOM T00:00 Jul-01 Tue End of nominal tour sequences EM 74 Ring CRX Ascending T23:23 Jul-02 Wed r = Rs EM 75 Apoapse T22:04 Jul-03 Thu Per = 7.1 d, inc = 75.5 deg, r = 20.9 Rs, phase = 22 deg EM 75 Earth OCC SATURN T10:10 Jul-07 Mon Duration = 66 min; egress = T11:16 EM 75 Earth OCC RING T10:20 Jul-07 Mon Duration = 33 min; egress = T10:52 Page 19

35 CASSINI TOUR EVENT SUMMARY ( Reference SPK, Version 7/27/05) DST / DTT = days since / until Titan, DSM = days since OTM Seq Rev Name Event Epoch (SCET) Date DOW DST DTT DSM Comment EM 75 75PA (nt) PANDORA T10:24 Jul-07 Mon Inbound km flyby, v = 22.9 km/s, phase = 103 deg EM 75 Sun OCC SATURN T10:27 Jul-07 Mon Duration = 46 min; egress = T11:14 EM 75 Sun OCC RING T10:29 Jul-07 Mon Duration = 24 min; egress = T10:53 EM 75 Ring CRX Descending T10:55 Jul-07 Mon r = 2.70 Rs EM 75 OTM TI+P T11:07 Jul-07 Mon D/L start, burn ~6h later. Backup D/L 147T19:43 EM 75 75ME (nt) METHONE T11:09 Jul-07 Mon Inbound km flyby, v = 22.3 km/s, phase = 81 deg EM 75 Periapse T11:18 Jul-07 Mon Per = 7.2 d, inc = 75.5 deg, r = 2.7 Rs, phase = 158 deg EM 75 Ring CRX Ascending T01:42 Jul-10 Thu r = Rs EM 76 Apoapse T23:20 Jul-10 Thu Per = 7.0 d, inc = 75.5 deg, r = 20.7 Rs, phase = 22 deg EM 76 Earth OCC SATURN T10:19 Jul-14 Mon Duration = 63 min; egress = T11:22 EM 76 Earth OCC RING T10:27 Jul-14 Mon Duration = 32 min; egress = T10:58 EM 76 76PM (nt) PROMETHEUS T10:35 Jul-14 Mon Inbound km flyby, v = 22.8 km/s, phase = 106 deg EM 76 Sun OCC SATURN T10:35 Jul-14 Mon Duration = 44 min; egress = T11:19 EM 76 Sun OCC RING T10:36 Jul-14 Mon Duration = 23 min; egress = T10:59 EM 76 Ring CRX Descending T11:01 Jul-14 Mon r = 2.69 Rs EM 76 76PL (nt) PALLENE T11:10 Jul-14 Mon Inbound km flyby, v = 21.9 km/s, phase = 70 deg EM 76 Periapse T11:23 Jul-14 Mon Per = 7.1 d, inc = 75.5 deg, r = 2.7 Rs, phase = 158 deg EM 76 76ME (nt) METHONE T11:33 Jul-14 Mon Outbound km flyby, v = 23.7 km/s, phase = 103 deg EM 76 76TI (nt) TITAN T21:55 Jul-15 Tue Outbound km flyby, v = 8.4 km/s, phase = 127 deg EM 76 Ring CRX Ascending T02:05 Jul-17 Thu r = Rs EM 76 OTM-159 ~APO T16:36 Jul-17 Thu D/L start, burn ~6h later. Backup D/L 190T17:07 EM 77 Apoapse T23:28 Jul-17 Thu Per = 7.0 d, inc = 75.4 deg, r = 20.7 Rs, phase = 22 deg EM 77 Earth OCC SATURN T10:31 Jul-21 Mon Duration = 60 min; egress = T11:32 EM 77 Earth OCC RING T10:39 Jul-21 Mon Duration = 30 min; egress = T11:09 EM 77 Sun OCC SATURN T10:46 Jul-21 Mon Duration = 42 min; egress = T11:28 EM 77 Sun OCC RING T10:46 Jul-21 Mon Duration = 23 min; egress = T11:09 EM 77 77PL (nt) PALLENE T11:02 Jul-21 Mon Inbound km flyby, v = 21.2 km/s, phase = 23 deg EM 77 Ring CRX Descending T11:11 Jul-21 Mon r = 2.69 Rs EM 77 77AT (nt) ATLAS T11:22 Jul-21 Mon Inbound km flyby, v = 23.0 km/s, phase = 148 deg EM 77 Periapse T11:33 Jul-21 Mon Per = 7.1 d, inc = 75.5 deg, r = 2.7 Rs, phase = 158 deg EM 77 77PN (nt) PAN T12:01 Jul-21 Mon Outbound km flyby, v = 25.0 km/s, phase = 117 deg EM 77 Ring CRX Ascending T02:33 Jul-24 Thu r = Rs EM 78 Apoapse T23:40 Jul-24 Thu Per = 7.0 d, inc = 75.4 deg, r = 20.7 Rs, phase = 22 deg EM 78 OTM TI-P T16:05 Jul-27 Sun D/L start, burn ~6h later. Backup D/L 200T16:36 EM 78 Earth OCC SATURN T10:49 Jul-28 Mon Duration = 57 min; egress = T11:46 EM 78 Earth OCC RING T10:55 Jul-28 Mon Duration = 28 min; egress = T11:23 EM 78 78PL (nt) PALLENE T10:59 Jul-28 Mon Inbound km flyby, v = 21.8 km/s, phase = 65 deg EM 78 78PN (nt) PAN T11:01 Jul-28 Mon Inbound km flyby, v = 23.0 km/s, phase = 113 deg EM 78 Sun OCC RING T11:02 Jul-28 Mon Duration = 22 min; egress = T11:24 EM 78 Sun OCC SATURN T11:03 Jul-28 Mon Duration = 40 min; egress = T11:42 EM 78 Ring CRX Descending T11:26 Jul-28 Mon r = 2.69 Rs EM 78 Periapse T11:48 Jul-28 Mon Per = 7.1 d, inc = 75.4 deg, r = 2.7 Rs, phase = 158 deg EM 78 78PM (nt) PROMETHEUS T11:51 Jul-28 Mon Outbound km flyby, v = 23.5 km/s, phase = 125 deg EM 78 78TI (t) [T45] TITAN T02:20 Jul-31 Thu Outbound 3980 km flyby, v = 6.1 km/s, phase = 7 deg Page 20

36 Day of Year, Week of Year, and OWLT Calendar for Cassini: 2005 January 2005 February 2005 March 2005 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :07 1:07 1:08 1:08 1:08 1:08 1:08 1:08 1:10 1:10 1:10 1:10 1:10 1: :07 1:07 1:07 1:07 1:07 1:07 1:07 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:10 1:11 1:11 1:11 1:11 1:11 1: :07 1:07 1:07 1:07 1:07 1:07 1:07 1:08 1:08 1:09 1:09 1:09 1:09 1:09 1:11 1:11 1:11 1:12 1:12 1:12 1: :07 1:07 1:07 1:07 1:07 1:07 1:07 1:09 1:09 1:09 1:09 1:09 1:09 1:10 1:12 1:12 1:12 1:12 1:13 1:13 1: :07 1:07 1:07 1:07 1:07 1:07 1:07 1:10 1:13 1:13 1:13 1: :07 April 2005 May 2005 June 2005 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :14 1:14 1:14 1:18 1:21 1:21 1:21 1:22 1: :14 1:14 1:14 1:14 1:15 1:15 1:15 1:18 1:18 1:18 1:18 1:18 1:18 1:19 1:22 1:22 1:22 1:22 1:22 1:22 1: :15 1:15 1:15 1:15 1:16 1:16 1:16 1:19 1:19 1:19 1:19 1:19 1:19 1:19 1:22 1:22 1:22 1:23 1:23 1:23 1: :16 1:16 1:16 1:16 1:16 1:17 1:17 1:20 1:20 1:20 1:20 1:20 1:20 1:20 1:23 1:23 1:23 1:23 1:23 1:23 1: :17 1:17 1:17 1:17 1:17 1:18 1:20 1:21 1:21 1:21 1:21 1:21 1:21 1:23 1:23 1:23 1: :21 1:21 July 2005 August 2005 September 2005 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :23 1:23 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:22 1:22 1:22 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:23 1:22 1:22 1:22 1:22 1:22 1:22 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:23 1:23 1:23 1:23 1:23 1:23 1:23 1:22 1:21 1:21 1:21 1:21 1:21 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:23 1:23 1:23 1:23 1:23 1:23 1:23 1:21 1:21 1:21 1:21 1:20 1:20 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:23 1:23 1:23 1:20 1:20 1:20 1:20 1:20 October 2005 November 2005 December 2005 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :20 1:19 1:16 1:15 1:15 1:15 1:15 1:15 1:12 1:11 1:11 1: :19 1:19 1:19 1:19 1:19 1:19 1:19 1:15 1:15 1:14 1:14 1:14 1:14 1:14 1:11 1:11 1:11 1:11 1:11 1:11 1: :18 1:18 1:18 1:18 1:18 1:18 1:18 1:14 1:14 1:13 1:13 1:13 1:13 1:13 1:10 1:10 1:10 1:10 1:10 1:10 1: :18 1:17 1:17 1:17 1:17 1:17 1:17 1:13 1:13 1:13 1:12 1:12 1:12 1:12 1:10 1:09 1:09 1:09 1:09 1:09 1: :17 1:16 1:16 1:16 1:16 1:16 1:16 1:12 1:12 1:12 1:09 1:09 1:09 1:09 1:09 1:

37 Day of Year, Week of Year, and OWLT Calendar for Cassini: 2006 January 2006 February 2006 March 2006 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :09 1:08 1:08 1:08 1:08 1:08 1:09 1:09 1:09 1:09 1: :08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:09 1:10 1:10 1:10 1:10 1:10 1: :08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:10 1:10 1:10 1:10 1:10 1:11 1: :08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:09 1:09 1:09 1:11 1:11 1:11 1:11 1:11 1:11 1: :08 1:08 1:08 1:08 1:08 1:08 1:08 1:09 1:09 1:12 1:12 1:12 1:12 1: :08 1:08 April 2006 May 2006 June 2006 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :12 1:12 1:16 1:16 1:17 1:17 1:17 1:17 1:17 1:20 1:21 1:21 1: :13 1:13 1:13 1:13 1:13 1:13 1:13 1:17 1:17 1:18 1:18 1:18 1:18 1:18 1:21 1:21 1:21 1:21 1:21 1:21 1: :14 1:14 1:14 1:14 1:14 1:14 1:14 1:18 1:18 1:18 1:19 1:19 1:19 1:19 1:22 1:22 1:22 1:22 1:22 1:22 1: :14 1:15 1:15 1:15 1:15 1:15 1:15 1:19 1:19 1:19 1:20 1:20 1:20 1:20 1:22 1:22 1:22 1:23 1:23 1:23 1: :15 1:15 1:16 1:16 1:16 1:16 1:16 1:20 1:20 1:20 1:23 1:23 1:23 1:23 1:23 July 2006 August 2006 September 2006 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :23 1:23 1:25 1:25 1:25 1:25 1:25 1:25 1:24 1:24 1: :23 1:23 1:24 1:24 1:24 1:24 1:24 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:24 1:24 1:24 1:24 1:24 1:23 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:25 1:25 1:24 1:24 1:24 1:24 1:24 1:23 1:23 1:23 1:23 1:23 1:23 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:24 1:23 1:23 1:23 1:23 1:23 1:23 1: :24 1:24 1:24 1:24 1:24 1:25 1:25 1:24 1:24 1:24 1:24 1:22 1:22 1:22 1:22 1:22 1: :25 October 2006 November 2006 December 2006 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :22 1:18 1:18 1:18 1:18 1:18 1:14 1:14 1: :22 1:22 1:21 1:21 1:21 1:21 1:21 1:17 1:17 1:17 1:17 1:17 1:17 1:17 1:14 1:13 1:13 1:13 1:13 1:13 1: :21 1:21 1:21 1:20 1:20 1:20 1:20 1:16 1:16 1:16 1:16 1:16 1:16 1:16 1:13 1:13 1:12 1:12 1:12 1:12 1: :20 1:20 1:20 1:20 1:20 1:20 1:19 1:15 1:15 1:15 1:15 1:15 1:15 1:15 1:12 1:12 1:12 1:12 1:11 1:11 1: :19 1:19 1:19 1:19 1:19 1:19 1:18 1:15 1:14 1:14 1:14 1:11 1:11 1:11 1:11 1:11 1:10 1:

38 Day of Year, Week of Year, and OWLT Calendar for Cassini: 2007 January 2007 February 2007 March 2007 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :10 1:10 1:10 1:10 1:10 1:10 1:10 1:08 1:08 1:08 1:08 1:09 1:09 1:09 1: :10 1:10 1:10 1:09 1:09 1:09 1:09 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:09 1:09 1:09 1:09 1:09 1:09 1: :09 1:09 1:09 1:09 1:09 1:09 1:09 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:09 1:09 1:09 1:10 1:10 1:10 1: :09 1:09 1:09 1:09 1:09 1:09 1:09 1:08 1:08 1:08 1:08 1:08 1:08 1:08 1:10 1:10 1:10 1:10 1:10 1:10 1: :08 1:08 1:08 1:09 1:09 1:09 1:10 1:11 1:11 1:11 1:11 1:11 April 2007 May 2007 June 2007 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :11 1:15 1:15 1:15 1:15 1:15 1:16 1:19 1:19 1: :11 1:11 1:12 1:12 1:12 1:12 1:12 1:16 1:16 1:16 1:16 1:16 1:16 1:17 1:19 1:20 1:20 1:20 1:20 1:20 1: :12 1:12 1:12 1:12 1:13 1:13 1:13 1:17 1:17 1:17 1:17 1:17 1:17 1:18 1:20 1:21 1:21 1:21 1:21 1:21 1: :13 1:13 1:13 1:13 1:13 1:14 1:14 1:18 1:18 1:18 1:18 1:18 1:18 1:19 1:21 1:21 1:21 1:22 1:22 1:22 1: :14 1:14 1:14 1:14 1:14 1:14 1:15 1:19 1:19 1:19 1:19 1:22 1:22 1:22 1:22 1:22 1: :15 July 2007 August 2007 September 2007 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :23 1:25 1:25 1:25 1:25 1:25 1:25 1: :23 1:23 1:23 1:23 1:23 1:23 1:23 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1: :23 1:23 1:23 1:23 1:24 1:24 1:24 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:24 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:24 1:24 1:24 1:24 1:24 1:24 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:25 1:25 1:25 1:25 1:25 1:24 1:24 1:24 1:24 1:24 1:24 1: :25 1:25 October 2007 November 2007 December 2007 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :24 1:23 1:23 1:23 1:23 1:23 1:23 1:20 1:20 1:20 1:20 1:16 1: :23 1:23 1:23 1:23 1:23 1:22 1:22 1:20 1:20 1:20 1:19 1:19 1:19 1:19 1:16 1:16 1:16 1:16 1:16 1:15 1: :22 1:22 1:22 1:22 1:22 1:22 1:22 1:19 1:19 1:19 1:19 1:19 1:18 1:18 1:15 1:15 1:15 1:15 1:15 1:15 1: :22 1:22 1:21 1:21 1:21 1:21 1:21 1:18 1:18 1:18 1:18 1:18 1:17 1:17 1:14 1:14 1:14 1:14 1:14 1:14 1: :21 1:21 1:20 1:17 1:17 1:17 1:17 1:17 1:13 1:13 1:13 1:13 1:13 1:13 1:

39 Day of Year, Week of Year, and OWLT Calendar for Cassini: 2008 January 2008 February 2008 March 2008 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :12 1:12 1:12 1:12 1:12 1:12 1:10 1:10 1:09 1:09 1: :12 1:12 1:11 1:11 1:11 1:11 1:11 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1: :11 1:11 1:11 1:11 1:11 1:11 1:10 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1: :10 1:10 1:10 1:10 1:10 1:10 1:10 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:09 1:10 1:10 1:10 1:10 1:10 1: :10 1:10 1:10 1:10 1:09 1:09 1:09 1:09 1:09 1:10 1:10 1:10 1:10 1:10 1:10 1: :11 April 2008 May 2008 June 2008 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :11 1:11 1:11 1:11 1:11 1:11 1:14 1:14 1:14 1:14 1: :11 1:11 1:11 1:11 1:12 1:12 1:12 1:14 1:15 1:15 1:15 1:15 1:15 1:15 1:18 1:18 1:19 1:19 1:19 1:19 1: :12 1:12 1:12 1:12 1:12 1:12 1:13 1:15 1:16 1:16 1:16 1:16 1:16 1:16 1:19 1:19 1:19 1:20 1:20 1:20 1: :13 1:13 1:13 1:13 1:13 1:13 1:13 1:16 1:16 1:17 1:17 1:17 1:17 1:17 1:20 1:20 1:20 1:21 1:21 1:21 1: :14 1:14 1:14 1:17 1:17 1:18 1:18 1:18 1:18 1:21 1:21 1:21 1:21 1:21 1:22 1: :22 July 2008 August 2008 September 2008 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :22 1:22 1:22 1:22 1:22 1:23 1:25 1:25 1:25 1:26 1:26 1:26 1:26 1:26 1:26 1: :23 1:23 1:23 1:23 1:23 1:23 1:23 1:25 1:25 1:25 1:25 1:25 1:25 1:25 1:26 1:26 1:26 1:26 1:26 1:26 1: :23 1:23 1:24 1:24 1:24 1:24 1:24 1:25 1:25 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1: :24 1:24 1:24 1:24 1:24 1:24 1:24 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:25 1: :25 1:25 1:25 1:25 1:26 1:26 1:26 1:26 1:26 1:26 1:26 1:25 1:25 October 2008 November 2008 December 2008 Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su Mo Tu We Th Fr Sa Su :25 1:25 1:25 1:25 1:25 1:23 1:23 1:19 1:19 1:19 1:19 1:19 1:18 1: :25 1:25 1:25 1:25 1:25 1:25 1:25 1:23 1:22 1:22 1:22 1:22 1:22 1:22 1:18 1:18 1:18 1:18 1:18 1:17 1: :25 1:24 1:24 1:24 1:24 1:24 1:24 1:22 1:22 1:22 1:21 1:21 1:21 1:21 1:17 1:17 1:17 1:17 1:17 1:16 1: :24 1:24 1:24 1:24 1:24 1:23 1:23 1:21 1:21 1:21 1:21 1:20 1:20 1:20 1:16 1:16 1:16 1:16 1:16 1:16 1: :23 1:23 1:23 1:23 1:23 1:20 1:20 1:20 1:20 1:19 1:19 1:19 1:15 1:15 1:15

40

41 Table B.1: Saturn Geometric Quantities Quantity Value Units Solar distance, mean 1430 million km 9.56 AU Solar distance, min 1350 million km 9.02 AU Orbital Solar distance, max 1510 million km Quantities AU Siderial orbit period days years Mean orbital velocity 9.64 km/s Orbital eccentricity Inclination to ecliptic 2.49 degrees Equatorial radius at 100 mbar =Rs km Polar radius at 100 mbar km Equatorial radius at 1 bar km Polar radius at 1 bar km J2 (unnormalized) Mass 5.69E+26 kg 95.2 Earth masses GM (planet centered) km^3/s^2 Volume 8.25E+23 cubic meters Planetary 764 Earth volumes Quantities Rotation period, kilometric hours Rotation period, equatorial hours Axial tilt degrees Atmospheric temp. at 1 bar 134 degrees Kelvin Effective temperature 95 degrees Kelvin Visual geometric albedo 0.47 Bolometric Bond albedo 0.34 Mean density g/cm3 Mean gravity at 1 bar m/s Earth gravities Constituent gases H2, He, CH4, NH3 Magnetic dipole moment gauss Rs3 Field 4.70E+28 gauss cm3 Quantities Magnetic dipole tilt < 1 degrees Magnetic dipole offset 0.04 Rs

42 Distance Distance Orbital Mean Orbital Orbital Orbital Satellite or Ring from Saturn from Saturn Period Velocity Inclination Eccentricity Name (km x 1000) (Saturn radii of km) (days) (km/sec) (degrees) D RING (inner edge) C RING (inner edge) (D ring outer edge) Maxwell Gap B RING (inner edge) (C ring outer edge) CASSINI div. (inner edge) B ring (outer edge) A RING (inner edge) (Cassini div. outer edge) Table B.2A: Saturnian Satellites - Orbital Geometry Encke Division (inner edge) Pan Encke Division (outer edge) Keeler Gap (A ring outer edge) Atlas Prometheus F RING (inner edge) F RING (outer edge) Pandora Epimetheus (var.) Janus (var.) G RING (inner edge) G RING (outer edge) Mimas E RING (approximate inner edge) Enceladus Tethys Telesto Calypso Dione Helene (E ring approx. outer edge) Rhea Titan Hyperion Iapetus Phoebe

43 Table B.2B: Saturnian Satellites - Body Characteristics Mean Alternate Satellite or Ring Radius* GM Density Observed Features Names Discovery Name (km) (km^3/s^2) (g/cm3) D RING (inner edge) C RING (inner edge) (D ring outer edge) D: very thin, not well defined; seen best in forwardscattered light C: very complicated grooved region; many ringlets of regular ordering Crepe ring Pioneer C ring: W.C. & G.P Bond & C. W. Tuttle 1850 Maxwell Gap B RING (inner edge) (C ring outer edge) CASSINI div. (inner edge) B ring (outer edge) A RING (inner edge) (Cassini div. outer edge) B: brightest ring; highly complex; thousands of ringlets; ring spokes; redder particles Cassini division: most prominent gap; caused by half-period resonance with Mimas; faint ringlets A: many ringlets & minor gaps; darker & more transparent than B B ring: C. Huygens 1659* division: G. D. Cassini 1675 A ring: C. Huygens 1659* Encke Division (inner edge) has faint ringlets J. F. Encke 1837 Pan S13 S18 Voyager (Showalter) Encke Division (outer edge) Keeler Gap (A ring outer edge) Atlas 18.5 x 17.2 x elongated; may control A ring outer edge Prometheus 74 x 50 x ~0.70 shepherd satellite to F ring with Pandora F RING (inner edge) F RING (outer edge) "braided" ring with separate strands; shepherded by Prometheus and Pandora Pandora 55 x 44 x ~0.70 shepherd satellite to F ring with Prometheus Epimetheus 69 x 55 x ~0.70 irregular; may have been joined with Janus Janus 97 x 95 x ~0.67 irregular; trades orbits with Epimetheus G RING (inner edge) G RING (outer edge) Mimas E RING (approximate inner edge) Enceladus Tethys 209 x 196 x x 247 x x 528 x extremely tenuous & optically thin; seen best with forward-scattered light; has denser core extremely tenuous & optically thin; seen best with forward-scattered light; has denser core giant crater Herschel on leading hemisphere; icy surface; may be covered with water frost E: thought to be sustained by Enceladus; density peaks at Enceladus' orbit complex & varied geological evolution; craters; plains; crustal movements; may be E ring source almost pure ice; large trench Ithaca Chasma (4-5km deep); large 400km crater Odysseus Telesto 15 x 12.5 x co-orbital with Tethys, 60 ahead (L4) Calypso 15 x 8 x co-orbital with Tethys, 60 behind (L5) Dione cratered leading hemisphere; wispy features on trailing hemisphere Helene co-orbital with Dione 60 ahead (L4) 1980 S28 S S27 S S26 S S3 S S1 S10 Voyager (Terrile) Voyager (Collins & Carlson) Pioneer Voyager (Collins & Carlson) Fountain & Larson 1978 Fountain & Larson 1978 detected Pioneer confirmed Voyager detected Pioneer confirmed Voyager S1 Herschel 1789 Voyager S2 Herschel 1789 S3 G. D. Cassini S13 S S25 S14 Smith et al 1980 Smith et al 1980 S4 G. D. Cassini 1684 Dione B 1980S6 S12 Lacques & Lecacheaux 1980 (E ring approx. outer edge) Rhea Titan Hyperion 180 x 140 x Iapetus Phoebe 115 x 110 x largest icy satellite; dark trailing hemisphere; densely cratered equator largest of the satellites; N2, He atmosphere; aerosols, hydrocarbons; surface temp. = 92 K; orangish disk; darker n. hemisphere; H2 torus irregular shape; long axis not pointed at Saturn (perhaps due to recent collision); dark surface; chaotic orbit MUCH darker leading hemisphere; ring of dark material near division retrograde orbit; only satellite not tidally locked; ~9hr rotation; dark surface; roughly spherical; may be captured body *Some bodies list 3-axis radii when available corresponding to sub-saturn equatorial radius, along orbit eq. radius, and polar radius. Ring values indicate width ( R) of ring. S5 Cassini 1672 S6 Huygens 1655 S7 Bond 1848 S8 G. D. Cassini 1671 S9 Pickering 1898

44

45 2.0 OPERATIONS OVERVIEW The mission design has a long (almost 7 year) cruise to get the spacecraft to Saturn and a 4 year tour in orbit around Saturn. During the cruise phase, the priority is placed on essential engineering, navigation, and science instrument maintenance, calibrations, and checkout. Some limited science collection is conducted, but is generally constrained to those activities required for tour readiness, or unique science opportunities that are in line with the program science objectives. A typical week in cruise would contain two downlink passes and have a handful of engineering activities as well as a low level of science observations. During early cruise, the spacecraft stayed on Earth-point most of the time due to thermal constraints; in later cruise, the spacecraft occasionally articlates to collect data from a particular target. During approach science, beginning in January 2004, intensive tour-like science observations begin. On a typical day in the Cassini tour, the spacecraft collects science data for 15 hours by orienting the spacecraft at a variety of targets. One instrument at a time controls the pointing of the spacecraft, and other instruments may ride along and collect data at the same time. Ride-alongs or collaborative data collection is often negotiated between the science teams. The remaining 9 hours is spent in one block on Earth-point, downlinking (or playing back) the data. During downlink since one axis of the spacecraft must be fixed to Earth - the spacecraft can only spin about the Z axis and collect fields, particles & waves data. This sweeping during playback allows three dimensional and temporal variations in the fields and particles environment to be measured. Control of the spacecraft is done, for the most part, from autonomous sequences stored onboard the spacecraft. Spacecraft sequencing uses a combination of centralized commands (for control of the system level resources) and instrument commands issued by the Command and Data Subsystem (CDS) and the instrument microprocessors to conduct activities and maintain the health and safety of the spacraft. Instrument data is formatted (including editing or compression) within the instrument microprocessor, and then collected on the spacecraft bus by the CDS on a schedule determined by the active telemetry mode. Packets from the engineering subsystems and instruments are assembled into frames and stored on the Solid State Recorder or inserted directly into the downlink telemetry stream. The spacecraft provides system level services for each of the twelve science investigations. These services include instrument command delivery, telemetry collection and transmission, spacecraft pointing and attitude stability, power, and thermal control. The spacecraft is flown with sufficient margins to allow the instruments to operate fairly independently from each other, and with a minimum of real-time ground intervention, but still allow for collaborative, synergistic collection of data. The Cassini spacecraft operates in a series of standard well-characterized configurations, referred to as "operational modes," and transitions between them use "fixed sequences." Since there is insufficient power to operate all instruments simultaneously, operational modes have been defined to balance the science return with the need to constrain operational complexity and cost in the planning and sequencing of science observations. Within an operational mode, any science and spacecraft activities are allowed that do not violate either the mode definition or other applicable constraints. The definition of each mode mirrors a common category of activities (such as maneuvers, or downlink to Earth) that are expected to be done often during the mission. Certain non-repetitive activities will be done with unique sequences of commands rather than operational modes. Non-variable but repetitive activities that are not done within an operational mode are called fixed sequences. These sequences are developed and validated once for use multiple times. 2.1 Ground Planning & Coordination Spacecraft operations will be centralized at JPL. The science teams are led using a distributed operations structure to allow scientists to operate their instruments from their home 2-1

46 institutions with the minimum interaction necessary to collect their data. Specific functions provided centrally by JPL for the scientists include mission planning, sequence integration, sequence and command radiation, spacecraft telemetry data collection/processing (packet extraction)/storage, spacecraft monitoring and performance maintenance, Facility Instrument health and safety monitoring, and spacecraft navigation. The sequencing process is a hierarchical step-wise refinement process, starting with general goals, to high-level sequence components, and ends with low-level commanding. Sequence planning begins with long-range plans generated by the mission planners. Consumable allocations, margin policy, long-range DSN agreements, guidelines & constraints, and the operational strategies documented in this section guide the initial sequence design. The science planning team works with the mission planning, spacecraft and other offices to generate a conflict-free activity plan of integrated science and engineering activities. Both the distributed science teams and engineering subsystem representatives submit activity requests which are integrated by the science planning team. Conflicts between science activities are resolved within the science planning team, and conflicts between engineering activities are resolved within the spacecraft office, with help from the science planning team. Conflicts between science and engineering activities are resolved with participation from all element representatives, with the mission planning office as the liaison when necessary. Once the conflict-free activity plan is completed, with scheduled activities, DSN passes, instrument pointing, and data allocations, the sequence virtual team integrates the plan into a conflict-free sequence and generates, verifies and validates all related commands to be sent to the spacecraft, except for instrument internal commands. The sequence virtual team is also responsible for all system-level real-time commands associated with the sequence, and monitors the progress of the activities until the sequence is complete. During cruise, sequences largely make use of commands and scripts inherited from spacecraft testing during the Assembly, Test, and Launch Operations (ATLO) phase. Repeatable sequence components (i.e. modules) are developed slowly as experience is gained in operating the spacecraft. Some science is collected during cruise in order to gain experience with instrument operations and prepare the instrument and instrument teams for tour. During the later portions of cruise, the Science Operations Plan (SOP) is developed as the detailed plan of tour activities. The SOP is a conflict-free listing of all observations and engineering activities, a constraint-checked pointing profile, and data volume allocations that would provide an acceptable level of science required to meet the primary mission objectives. As tour approaches, any high-level trade studies and changes in operations strategy are incorporated via an SOP aftermarket process, which is also used for further science optimization. In the few months before execution, the SOP sequences are refined as necessary via a short-term update process and final constraint checking, integration, validation, and command generation are performed. Figure 2-1 illustrates the processes for sequence generation for tour. The flight team is sized for nominal operations, and anomaly staffing is done by augmentation with personnel (with spacecraft expertise) from the JPL technical divisions. Only a few specific contingency plans are developed (mostly dealing with launch and Earth flyby events). Identification and prioritization of these plans has been done as needed to reduce the risk to the mission within the cost constraints. This effort is documented in the Risk Management Plan. Updates to a sequence after it has been validated are limited. Changes to an instrument s internal commands or instrument memory may be accomplished via the instrument-internal real-time command process and can range from the replacement of an entire block of instructions to the update of a few words in instrument memory. Updates to the tables which store the locations of various mission targets may also be uplinked if the spacecraft or target ephemeris has changed to refine pointing for planned observations. Tweaks to the stored sequence for other observation timing changes are also possible. These changes should be 2-2

47 limited as much as possible, and must be approved by the sequence teams and/or the project manager. 2.2 Spacecraft Description Figure 2-1 Planning Processes for Tour The Cassini spacecraft is a three-axis-stabilized spacecraft, depicted in figure 2-2. The origin of the Orbiter coordinate system lies at the center of the field joint between the Bus and the Upper Equipment Module Upper Shell Structure Assembly. The Z-axis emanates from the origin and is perpendicular to a plane generated by the mating surfaces of the Bus. The +Z-axis is on the propulsion module side of the interface. The Z axis is aligned with the mechanical boresight fo the high gain antenna. The X-axis emanates from the origin The -X-axis points toward the Huygens Probe. The Y-axis is mutually perpendicular to the X and Z axes, with the +Y axis oriented along the magnetometer boom. The remote sensing pallet is mounted on the +X side of the spacecraft, the mag boom extends in the +Y direction, and the +Z axis completes the orthogonal body axes in the direction of the main engine. The primary remote sensing boresights view in the -Y direction, the probe will be ejected in the -X direction, the HGA boresight is in the -Z direction, the main engine exhaust is in the +Z direction with the thrust in the -Z direction. Two important directions to bear in mind are the HGA placement in the minus Z direction and the remote sensing instrument boresights along the minus Y direction. The rotational motion of the spacecraft about the coordinate system axes is commonly called simply a turn. The terms roll, pitch and yaw are generally discouraged because of possible ambiguity of the axis specified. However, roll, pitch and yaw are defined about the +Z, +Y, and +X directions respectively. The right-hand rule is used as to directions, e.g. during a positive roll while on Earth-line, the spacecraft will be spinning clockwise as seen from the Earth. (Point the right thumb along the +Z direction, i.e. along the main engines in this case away from the Earth. The fingers of the right hand indicate the direction of rotation as they curl closed in this case, clockwise looking from the Earth.) The main body of the spacecraft is formed by a stack consisting of the lower equipment module, the propulsion module, the upper equipment module, and the HGA. Attached to this stack are the remote sensing pallet, the fields and particles pallet, and the Huygens Probe system. The two equipment modules are also used for external mounting of the magnetometer boom and the three radioisotope thermoelectric generators (RTGs) which supply the spacecraft power. Measurements of the output of the radioisotope thermoelectric generators indicate a beginning-of-life power of 876 ± 6 Watts and estimates of 740 Watts at SOI and 692 Watts at end of mission. The spacecraft electronics bus is part of the upper equipment module and 2-3

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49 carries the electronics to support the spacecraft data handling, including the command and data subsystem and the radio frequency subsystem. The Spacecraft stands 6.8 meters (22.3 ft) high. Its maximum diameter, the diameter of the HGA, is 4 meters (13.1 ft). Therefore, the HGA can fully shield the rest of the spacecraft (except the deployed MAG boom and RPWS antennas) from sunlight when the HGA is pointed within ±2.5 of the Sun. The dry mass of the spacecraft is 2523 kg, including the Huygens Probe system and the science instruments. The best estimate of the actual spacecraft mass at separation from the Centaur was kg. The spacecraft mass properties are listed in Table Science Instruments There are 12 science instrument subsystems grouped into three larger groups: Optical Remote Sensing, Fields/Particles/Waves and Microwave Remote Sensing. The Optical Remote Sensing instruments are mounted on the Remote Sensing Pallet (RSP) rigidly attached to the UEM. The Fields, Particles, and Waves (FPW) instruments are mounted in several locations on the spacecraft. The MAG sensors are located on the extensible MAG boom, attached to the top of the UEM. A small pallet, also mounted on the UEM, carries INMS, MIMI LEMMS and CHEMS, and CAPS. MIMI INCA, CDA, and the RPWS antennas and Magnetic Search Coils (MSC) are attached elsewhere on the UEM. (Note that the MIMI INCA is a remote sensing instrument with the capability of imaging the charged particle population of Saturn's magnetosphere. There are two microwave sensing instruments: RADAR and the Radio Science Subsystem (RSS). The RADAR Flight Instrument System consists of the following subsystems: the Radio Frequency Electronics Subsystem (RFES), the Digital Subsystem (DSS), the Energy Storage Subsystem (ESS), and the Antenna Subsystem. DSS and ESS are located in one of the equipment bays below the HGA. RFES is in a penthouse-like attachment over the bay. The principal component of the Antenna Subsystem is the five-beam Ku-band HGA feed. RADAR shares the HGA with the RSS for both its active (Synthetic Aperture RADAR imaging and altimetry) and passive (radiometry) operations. The Radio Science instrument is composed of elements located in the DSN and onboard the spacecraft. The flight Radio Science instrument consists of the Radio Frequency Instrument Subsystem (RFIS) and elements of the RFS. The main assemblies of the RFIS are the Ka-band Exciter, the Ka-band TWTA, the Ka-band Translator, and the S-band transmitter. In addition, the HGA is used as part of the Radio Science Instrument to receive the X- and Ka-band signals and to transmit at X-, Ka-, and S-bands The Huygens Probe System The Probe System consists of two elements: the Huygens Probe itself, which enters the Titan atmosphere near the beginning of the tour 22 days after separation from the Orbiter; and the Probe Support Equipment (PSE) consisting of those parts of the System which remain attached to the Orbiter in support of the Probe Mission. 2-4

50 Figure 2.3 Remote Sensing Pallet Figure 2.4 Fields & Particle Pallet 2-6

51 FIGURE 2.5 Fields of View for Cassini Science Instruments 2-7

52 PROJECTION ON SKY (ALONG Y-AXIS) UVIS narrow (0.75 mrad by 61 mrad) UVIS medium (1.5 mrad by 61 mrad) UVIS wide (6 mrad by 61 mrad) ISS NAC* (6.1 mrad) ISS WAC (61.2 mrad) CIRS (4.3 mrad, center offset from optical axis by 4 mrad) CIRS (2 at 2.9 x 0.3 mrad, 0.67 mrad separation between inside edges) VIMS Visible & IR Frame (32 mrad) *ISS NAC calibration shows offset by mrad in X and mrad from in Z from the -Y axis. Other instruments are shown in their nominal positions. +X +Y +Z Spacecraft Axes Figure 4.8 Fields of view for the Optical Remote Sensing Instruments. 2-8

53 Figure 4.9 Huygens Probe Composition 2-9

54 2.3 Tour Description & Strategies Each orbit about Saturn is assigned a rev number from 1 to N incrementing at apoapsis (where one orbit ends, and the next begins). The partial orbit from SOI to the first apoapsis is orbit 0. Each satellite encounter is assigned a unique satellite encounter label consisting of a three digit rev number on which the encounter occurs followed by a two character body indicator. For the major nine satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, Iapetus, and Phoebe), the first two letters are unique and are used as the body indicator. Encounters of satellites occur either inbound (before Saturn periapsis) or outbound (after Saturn periapsis). Orbit orientation defines the location of apoapsis of the Saturn centered orbit with respect to the Sun direction which is an important consideration for observations of Saturn s magnetosphere and atmosphere. Orbit orientation may be defined by an angle or a local true solar time (LTST) as depicted in Figure 2.8. The orbit orientation angle is measured clockwise in the Saturn equatorial plane from the projection of the Saturn Sun line in the equatorial plane to the projection of the Saturn-apoapsis line. The local true solar time (LTST), measured in hours (or hh:mm:ss), is obtained by scaling the orbit orientation angle by (24 hours/360ϒ). SUN Projection of Saturn-Sun Direction in Saturn Equatorial Plane NOON LTST = 12:00 = 12 PM Orbit Orientation Angle = 90ϒ, Local True Solar Time (LTST) = 6 AM DUSK LTST =18:00 = 6 PM Saturn DAWN LTST = 06:00 = 6 AM S/C Orbit View From Saturn North Pole Projection of Saturn- Apoapsis Direction in Saturn Equatorial Plane MIDNIGHT / TAIL LTST = 0:00 = 12 AM Figure 2.8 Definition of Orbit Orientation The time available for observations of Saturn s lit side decreases as the orbit rotates toward the anti-sun direction. Arrival conditions at Saturn fix the initial orientation at about 90ϒ which is equivalent to 6 AM LTST. Due to the motion of Saturn around the Sun, the orbit orientation increases with time, at a rate of orientation of about 1ϒ/month, which over the four-year tour 2-10

55 results in a total rotation of about 48ϒ (3.2 hours) in the clockwise direction (as seen from above Saturn s north pole). Period-changing targeted flybys that rotate the line of apsides may be used to add to or subtract from this drift in orbit orientation. The petal plot shows how targeted flybys combine with orbit drift to rotate the orbit from the initial orientation clockwise most of the way around Saturn to near the Sun line. In the coordinate system used in this figure, the direction to the Sun is fixed. A targeted flyby is one where the orbiter s trajectory has been designed to pass through a specified aimpoint (latitude, longitude, and altitude) at closest approach. At Titan, the aimpoint is selected to produce a desired change in the trajectory using the satellite s gravitational influence. Flybys within a few thousand km of Titan must be targeted due to the large ΔV imparted by Titan. At targeted flybys of icy satellites, the aimpoint is generally selected to optimize the opportunities for scientific observations, since the gravitational influence of those satellites is small. However, in some cases the satellite s gravitational influence is great enough to cause unacceptably large ΔV penalties for some aimpoints, which makes it necessary to constrain the range of allowable aimpoints to avoid this penalty. If the closest approach aimpoint during a flyby is not controlled, the flyby is referred to as a non-targeted flyby. Flybys of Titan at distances greater than 11,000 km (with the notable exception of the Probe Titan flyby 003Tc) are non-targeted flybys. Flybys of satellites other than Titan at distances greater than a few thousand kilometers are usually non-targeted flybys. If the closest approach point is far from the satellite, or if the satellite s mass is small, the gravitational effect of the flyby can be small enough that the aimpoint at the flyby need not be tightly controlled in order to ensure a return path to Titan. However, the gravitational influence of the flyby is not the sole criteria for distinguishing between targeted and nontargeted flybys. Operations constraints on satellite encounter frequency may force some close icy satellite flybys(usually within a few days of a Titan flyby) to be non-targeted. Opportunities to achieve non-targeted flybys of smaller satellites occur frequently during the tour. These are important for global imaging. If the transfer angle between two Titan flybys is an integer multiple of 360ϒ (i.e., the two flybys encounter Titan at the same place in its orbit), the orbit connecting the two flybys is called a resonant orbit. The period of a Titan-resonant orbit is an integer multiple of Titan's 16 d orbital period. The plane of the transfer orbit between any two flybys is formed by the position vectors of the flybys with respect to Saturn. In this case, an infinite number of orbital planes connect the flybys; therefore, for resonant orbits, the plane of the transfer orbit can be inclined significantly to Saturn s equator. The Titan flyby altitude for resonant transfers is often the minimum permitted value of 950 km since maximum inclination change per flyby is usually desired. If two successive flybys encounter Titan at a different place in its orbit, the orbit connecting the two flybys called a non-resonant orbit. Non-resonant orbits have orbital periods which are not integer multiples of Titan's period. Non-resonant transfer orbits connect inbound Titan flybys to outbound Titan flybys, or visa versa. Except for the special case of a 180ϒ transfer, the Titan position vectors at successive encounters are not parallel (i.e., Titan is encountered at different locations in its orbit), and therefore the orbital plane formed by the position vectors of the two flybys is unique and lies close to Titan s orbital plane (which lies close to Saturn s equatorial plane). Nonresonant transfers therefore have near zero orbit inclination. The Titan flyby altitude for nonresonant transfers is usually much greater than the minimum flyby altitude value of 950 km since inclination is constrained to be near zero and thus the Titan gravity assist must be used solely to obtain a return trajectory to Titan. A 180ϒ transfer is a very special case of a Titan nonresonant transfer. In a 180ϒ transfer, the transfer angle between two Titan flybys is an odd multiple of 180ϒ. In this case, successive Titan encounters occur first at the ascending node of Titan s orbit and then the descending node, or visa versa. Only one 180ϒ transfer occurs in the tour. Significant inclination and orbit 2-11

56 orientation change are accomplished during a sequence of flybys which includes a 180ϒ transfer. RESONANT TRANSFER DEFINITION: Next Titan encounter occurs at SAME place in Titan's orbit as current encounter, i.e. s/c orbit is in resonance with Titan orbit. Used primarily for changing s/c orbit inclination or when already in an inclined orbit, changing s/c orbit period. Titan Orbit S/C Orbit Saturn n complete Titan revs per m complete s/c revs where n, m = 1, 2, 3,... Line of Nodes Titan at current encounter Titan at next encounter Figure 2.9 Definition of Resonant Transfer NONRESONANT TRANSFER DEFINITION: Next Titan encounter occurs at a DIFFERENT place in Titan's orbit as current encounter, i.e. s/c orbit is NOT in resonance with Titan orbit. Used primarily for changing s/c orbit orientation (local solar time of s/c orbit apoapsis). Titan Orbit Saturn Inbound Titan at next encounter.8 revs later Outbound S/C Orbit Titan at current encounter Sample Low Inclination Transfer Titan at current encounter Line of S/C Nodes = Saturn to Titan Direction Inbound Titan Orbit Saturn S/C Orbit Outbound Titan at next encounter 1.1 revs later Sample Inclined 180 deg. Transfer Transfers are from Titan outbound from Saturn to Titan inbound to Saturn or visa versa. S/C orbit plane must contain Titan at current encounter, Titan at next encounter, and Saturn. Therefore, s/c orbit inclination must be near zero unless Titan encountered at opposite sides of its orbit (i.e., 180 deg. transfer). Figure 2.10 Definition of Nonresonant and 180ϒ Transfer Table 2 shows a breakdown of the tour into segments and shows the main characteristics of each segment. Segments are delineated by Titan encounters since only at Titan encounters is the orbital geometry significantly altered. An expanded description of each segment follows. Recall that the first 3 digits of the encounter label are the rev number and that encounter labels in parentheses use the navigation encounter numbering scheme (1 to n). 2-12

57 Encounte rs SOI-Tc (SOI-Tc) Tc-14TI (Tc-T7) Table 2.1 Tour Segment Characteristics Dates Figure Comments Jul , Jan Jan , Sep SOI, PRM, target for Probe mission at Tc, reduce period & inclination Reduce inclination to enable nonresonant transfer to establish optimal occultation geometry, raise inclination for Saturn/ring occultations and lower again to equator. Two targeted Enceladus flybys. 14TI-26TI (T7-T16) Sep 2005 Jul Rotate clockwise toward anti-sun direction to establish optimal magnetotail geometry. Targeted Hyperion, Dione, and Rhea flybys. 26TI-47TI Jul , Deep magnetotail passage initiating 180-deg. transfer sequence (including (T16-T33) Jun several revs for ring observations) 47TI-49TI Jun Rotate clockwise to optimize atmospheric observation and Saturn/ring occultation (T33-T35) Oct 2007 geometries 49TI-End Oct , Increase inclination to 75.6ϒ (maximum value in tour). Targeted Iapetus and (T35-T44) Jul Enceladus flyby. Last Titan flyby is 69TI (T44). SOI-Tc This tour segment has been significantly redesigned since the last Mission Plan release due Probe mission considerations. The remaining tour segments only contain a few tweaks to the latest T18-5 reference tour and will be described in subsequent segments. The spacecraft approaches Saturn from below the ring plane on a trajectory inclined about 17 with respect to Saturn s equator [ Saturn s equatorial plane is inclined 26.7 with respect to it s orbit around the Sun. Saturn s orbit is itself inclined 2.49 with respect to the ecliptic.]. The first Titan flyby is inbound due to Probe delivery considerations. In February 2000, it was discovered that the bit synchronizer of the Huygens receiver on the orbiter has a bandwidth that is too small to accommodate the Doppler shift of the relay signal. In order to recover the Probe mission, the redesign reduces the Doppler shift between the Probe and orbiter. To reduce the relay Doppler shift, the closest approach altitude of the orbiter at the Probe relay encounter (Tc) was raised to km which reduces the radial component of the orbiter s velocity relative to the Probe and hence the Doppler shift of the relay signal Three new Titan encounters: Ta, Tb, and Tc have been designed with a distant flyby during Probe delivery on Tc. These three initial Titan encounters replace the first two Titan encounters of the T18-5 tour. The new tour therefore contains an additional Titan flyby albeit at very high altitude. Following Tc, the trajectory rejoins the T18-5 tour at the 3TI (T3) encounter. After the 3TI encounter, the encounter times differ from those in T18-5 by less than 4 hours and the geometry of the encounters and occultations remain essentially the same. The orbiter s inclination is gradually reduced to enable a nonresonant transfer in the next tour segment needed to establish optimum Saturn/ring occultation geometry. Therefore, the initial series of Titan flybys must all take place at the same place in Titan s orbit (i.e. they all must be resonant, inbound flybys). The initial flybys quickly reduce period, as well as inclination, to maximize the number of Titan flybys in the tour. These three inbound, period-reducing flybys rotate the line of apsides counterclockwise (Figure 2.11). This moves the apoapse toward the Sun line which provides time for observations of Saturn s atmosphere and helps establish the geometry needed for near equatorial Saturn/ring occultations later in the tour. If the Probe cannot be delivered at the Tc flyby, a contingency trajectory exists that allows a second chance to deliver the Probe. This contingency retargets Tc to a lower altitude and introduces a new distant flyby, Td, for Probe delivery. However, this contingency causes Cassini to fall off of the tour and it doesn't return to the T18-5 tour until the 13TI (T6) flyby. In this case, the first two targeted Enceladus flybys will be lost as well as 3 of the 7 diametric Saturn/ring occultations. Due to the severe science impact of this contingency, every effort will be made to deliver the Probe on the nominal Tc encounter. 2-13

58 Tc-14TI (Tc-T7) (Figures 2.13 and 2.14) The 3TI (T3) flyby initiates a nonresonant inbound to outbound transfer that orients the line of nodes nearly normal to the Saturn-Earth line. This orientation minimizes the inclination required to achieve an occultation of Saturn and results in Saturn/ring occultations which are characterized by ingress and egress close to Saturn s equatorial plane (i.e., near-equatorial). The use of outbound flybys for the early tour dawn orbit orientation minimizes the Saturnspacecraft distance during these occultations which improves science return since the footprint" projected on the rings is minimized, improving the spatial resolution of the "scattered" radio signal observations. This is an important influence on the design of the tour. A targeted Enceladus (4EN, (E1)) flyby is obtained during the 3TI-5TI (T3-T4) nonresonant tranfer. Note that targeted flybys of the icy satellites such as 4EN are usually obtained on orbits which are also used to establish desired Saturn-relative geometries. The resonant outbound flybys 5TI (T4) and 6TI (T5) increase inclination to ~22ϒ to set up the Saturn/ring equatorial occultations. During the 6TI (T5) to 13TI (T6) segment, seven nearequatorial occultations of Earth and Sun by Saturn and its rings (one on each 18.2 d period orbit) occur. During these seven orbits, the orbiter crosses Saturn s equator near Enceladus orbit; on the fourth orbit, Enceladus and the spacecraft both arrive at nearly the same point in Enceladus orbit at the same time, and the second targeted flyby of Enceladus (11EN, (E2)) occurs. Enceladus gravity is too weak to displace inclination significantly from the value required to achieve occultations. The 13TI (T6) flyby decreases inclination once again to near Saturn's equator to enable a nonresonant transfer in order to begin the next tour segment. Unlike the last officially released tour, the 13TI (T6) flyby altitude was raised from 950 to ~4000 km in order to avoid a G ring crossing but the 14TI (T7) altitude was lowered from ~4000 to 950 km. These two Titan flybys therefore do not change the distribution of Titan flyby altitudes. 14TI-26TI (T7-T16) (Figure 2.15) The 14TI-17TI (T7-T8) nonresonant transfer initiates a series of alternating outbound/periodreducing and inbound/period-increasing flybys lasting about 10 months. These flybys are used to rotate the orbit apoapsis clockwise toward the magnetotail to establish the geometry required for a deep magnetotail passage. The period typically alternates between 23 d (outbound) and 39 d (inbound) with.8 to 1.1 revs between flybys since this sequence results in the most rapid change in orbit orientation. The only exceptions to this pattern were orbits used to obtain targeted icy satellites during these nonresonant transfers. Following the 14TI (T7) flyby, a 19 d period, 2.8 rev nonresonant transfer is used in order to achieve the first targeted flybys of Hyperion (15HY, (H1)) and Dione (16DI, (D1)) along the way. Compared to the last officially released tour, the Dione flyby aimpoint has been lowered in altitude (to 500 km) and changed in B-plane angle per PSG request. Similarly, following the 17TI (T8) flyby, a 28 d, 2.1 rev nonresonant transfer is utilized to obtain the first targeted Rhea (18RH, R1) flyby. 26TI-47TI (T16-T33) (Figures 2.16, 2.17) The 26TI (T16) flyby places apoapsis near the anti-sun line at an inclination of ~15ϒ to achieve passage through the current sheet in the magnetotail region. Apoapsis distance is about 49 R S, exceeding the 40 R S MAPS requirement associated with magnetotail passage. At distances this far from Saturn, the current sheet is assumed to be swept away from Saturn s equatorial plane by the solar wind. This flyby also initiates the 180ϒ transfer sequence. A series of 17 Titan flybys comprise the 180ϒ transfer sequence. A series of 9 resonant transfers, usually with period of 16 d, increases inclination and decreases orbit eccentricity to a point at which both the ascending and descending nodes of the spacecraft orbit are at Titan s orbital radius. At an inclination of ~59ϒ, a nonresonant 180ϒ transfer is then performed (the 2-14

59 orbit shown in bold in Figures 16 and 17), i.e., the true anomaly of Titan in its orbit at which it is encountered by the spacecraft on successive flybys differs by 180ϒ (actually 540ϒ). A series of 8 16 day period orbits then decreases inclination back to near zero and increases eccentricity back to its original value. Orbit orientation is changed by ~135ϒ to ~8 PM LTST over the 11 month sequence duration. Most Titan flyby altitudes are at the minimum permitted value of 950 km in order to maximize the inclination and eccentricity change at each flyby. Such low altitude Titan flybys are preferred for many science observations. The 31TI (T20) flyby reduces period to 12 days resulting in 4 revs over an interval of 48 d between Titan flybys in order to provide additional ORS observations of the rings at a time of favorable observational geometry. This 48-day interval also serves to reduce operational stress on the ground system. 47TI-49TI (T33-T35) (Figure 2.18) The 47TI (T33) and 48TI (T34) nonresonant transfers rotate the orbit petal further clockwise (toward noon) to enable Saturn atmospheric observations at both great distance (> 40 Rs) and low phase angle. This tour segment provides much of the long integration time daytime atmospheric observation opportunities. The nonresonant transfers also move the line of nodes closer to the Sun line in order to establish the geometry needed for near polar Saturn/ring occultations in the next tour segment. 49TI-End Baseline Mission (post 69TI) on Rev 74 (T35-post T44) (Figures 2.19 and 2.20) This segment is comprised solely of resonant transfers which gradually raise inclination to the maximum value attained in the tour. The first targeted Iapetus encounter (49IA (I1)) is obtained on the 49TI-50TI (T35-T36) resonant transfer at an inclination of ~6ϒ. Note that the ascending node on which this targeted Iapetus encounter is obtained differs ~180ϒ from the ascending node desired for the maximum inclination sequence. The desired ascending node for the maximum inclination segment places periapsis below the ring plane such that the spacecraft can view the illuminated side of the rings at Saturn periapsis (note Solar declination is negative during this time period). The third targeted Enceladus (61EN, (E3)) encounter is obtained on the 59TI-62TI (T41-T42) transfer. Note that this Enceladus flyby is occulted from the Sun at closest approach. Following the targeted 49IA (I1) Iapetus flyby, starting at 50TI (T36), a series of 10 outbound Titan resonant transfers are used increase inclination as much as possible for ring observations and in-situ fields and particles measurements. These resonant transfers continue until the end of the baseline tour on July 1, 2008 (rev 74) four years after insertion into orbit about Saturn. The LTST of these orbits is near noon to enable near polar Saturn/ring occultations at close distances. The maximum inclination possible is dictated primarily by the Titan-relative V-infinity (fixed), orbital period (free), and the number of Titan flybys (constrained by time left in tour) devoted to increasing inclination. The closest approach altitudes during this segment are kept at the minimum allowed value of 950 km to maximize inclination change at each flyby. The orbital period must be gradually reduced in order to further increase inclination which decreases the descending node crossing distance to the point where ring hazard avoidance becomes a limiting constraint. The orbital characteristics after the last Titan flyby in the tour, 69TI (T44), are a period of 7.1 d, inclination of 75.6ϒ, and descending node distance of 2.7 Rs. Five periapses are completed at this maximum inclination before the end of the baseline tour. The aimpoint at the last Titan flyby is chosen to target the orbiter to a Titan flyby on 7/31/08 (64 days and 9 revs after the 69TI (T44) flyby), providing the opportunity to proceed with more flybys during an extended mission, if resources allow. Nothing in the design of the tour precludes an extended mission. 2-15

60 Figure 2.11 Tour Segment SOI-Tc Side View Figure 2.12 Tour Segment Tc-14TI (Tc-T7) (+X parallel to Saturn to Sun direction, +Z Saturn N. Pole) 2-16

61 Figure 2.13 Tour Segment Tc-14TI (Tc-T7) Side View Figure 2.14 Tour Segment 14TI-26TI (T7-T16) [~Zero Inclination] (+X parallel to Saturn to Sun direction, +Z Saturn N. Pole) 2-17

62 Figure 2.15 Tour Segment 26TI-47TI (T16-T33) (+X parallel to Saturn to Sun direction, +Z Saturn N. Pole) Figure 2.16 Tour Segment 26TI-47TI (T16-T33) Side View 180ϒ Transfer Orbit i=59ϒ 2-18

63 Figure 2.17 Tour Segment 47TI-49TI (T33-T35) [~Zero Inclination] (+X parallel to Saturn to Sun direction, +Z Saturn N. Pole) Figure 2.18 Tour Segment 49TI-End Baseline Mission (post 69TI) on Rev 74 (T35-post T44) (+X parallel to Saturn to Sun direction, +Z Saturn N. Pole) 2-19

64 Figure 2.19 Tour Segment 49TI-End Baseline Mission (post 69TI) on Rev 74 (T35-post T44) Side View 2.4 Telecommunications The Radio Frequency Subsystem (RFS) provides the telecommunications facilities for the spacecraft and is used as part of the radio science instrument. For telecommunications, it produces an X-band carrier at 8.4 GHz, modulates it with data received from CDS, amplifies the X-band carrier power to produce 20 W from the Traveling Wave Tube Amplifiers (TWTA), and delivers it to the Antenna Subsystem (ANT). (The 20W is expected to degrade to about 19W by the start of the tour.) From ANT, RFS accepts X-band ground command/data signals at 7.2 GHz, demodulates them, and delivers the commands/data to CDS for storage and/or execution. The Ultra Stable Oscillator (USO), the Deep Space Transponder (DST), the X-band Traveling Wave Tube Amplifier (TWTA), and the X-band Diplexer are those elements of the RFS which are used as part of the radio science instrument. The DST can phase-lock to an X-band uplink and generate a coherent downlink carrier with a frequency translation adequate for transmission at X-, S-, or Ka-band. The DST has the capability of detecting a ranging modulation and of modulating the X-band downlink carrier with the detected ranging modulation. Differenced one-way ranging (DOR) tones can also be modulated onto the downlink. The DST can also accept the reference signal from the USO and generate a noncoherent downlink carrier. However, there are currently no plans to use the DOR tones for navigation. The ANTenna subsystem (ANT) provides a directional high gain antenna (HGA) for X-, Ka-, S- and Ku-band for transmitting and receiving on all four bands. Because of its narrow halfpower beam width of 0.14 deg for Ka-band, it must be accurately pointed. The HGA, and the low gain antenna 1 (LGA1) located on the HGA feed structure, are provided by the Italian 2-20

65 Space Agency. Another LGA (LGA2) is located below the Probe pointing in the -X direction. During the inner solar system cruise, the HGA is Sun-pointed to provide shade for the spacecraft. ANT provides two LGAs which allow one or the other to receive/transmit X-band from/to the Earth when the spacecraft is Sun-pointed. The LGAs also provide an emergency uplink/downlink capability while Cassini is at Saturn. The HGA downlink gain at X-band is 47dBi and the LGA1 peak downlink gain is 8.9 dbi. The X-band TWTA power is 20 watts. Telecommunications strategies are developed to use the three antennas (the HGA and two LGAs) to maximize science data return and visibility of the ground teams within the project and DSN constraints. Telecommunications with Cassini for the first 800-plus days of the mission is generally restricted to the spacecraft's low gain antennas (LGAs). During this time, it is necessary to use the high gain antenna (HGA) as a sunshade. Telemetry mode RTE-40 is used for most cruise downlink since it is generally the highest data rate achievable. Where advantageous, other modes such as PB&RTE-40, PB&RTE-200, RTE-948, RTE-158, or PB&RTE-948 are used when available and if Earth range and trajectory geometry permit. RTE-20 is the lowest data rate that the spacecraft will use for downlink in a non-emergency situation, whereas PB&RTE-40 is the lowest data rate available for playback of data from the SSR. The spacecraft transmits and receive through Low Gain Antenna 1 (LGA1) for the majority of the early cruise periods. LGA1 is preferred since the spacecraft does not have to be constrained in roll attitude as with LGA2, although the Earth-Spacecraft-Sun angle generally dictates which LGA is required. There is a 25 day period at launch plus 14 months when the Earth- Spacecraft-Sun (EPS) angle is sufficiently small to allow use of the HGA for telecommunications. This is the first post-launch functional checkout of the science instruments. After the 25 days until early 2000, telecommunications must again use the LGAs at low rates (except very near Earth). Following the switch to the HGA in February 2000, the telecommunications link capability is improved significantly and much higher rates are possible, allowing more data-intensive engineering and science activities throughout the rest of the mission. The normal DSN coverage for cruise is two passes per week, for spacecraft monitoring, data return and navigation. During the tour the Cassini telecommunications support requirement is one pass per day due to the high level of science activity expected. These basic coverages represent a general commitment of DSN loading. Radio science measurements (e.g., occultations) will be accommodated on an occasional basis and will generally be added on top of the one pass per day schedule. The specific site used is chosen based on DSN workload, maximum downlink rate, conflicts with other missions, or other issues. Typically, however, the project will select Goldstone regularly since it has good downlink capability and using the same station allows for repeated activities (e.g. 15 hours collect, 9 hours downlink). Madrid also has good downlink rate and is desired by navigation to check for station-specific tracking biases. Canberra is undesirable due to its poor geometry and downlink rate. Antenna switch times are based on Earth range and on Earth-Spacecraft-Sun (EPS) geometry. If the EPS angle is greater than 44 degrees, LGA2 offers better downlink performance. However, if the EPS angle is less than 44 degrees, LGA1 should be used. LGA2 must not be used during probe checkouts due to its proximity to the probe and resulting interference. Table 5.1 defines the antenna usage periods for early cruise. Table 2.2 Antenna Usages (Year - Day Of Year) LGA1 Periods LGA2 Periods HGA Periods to to to to to to to to EOM 2-21

66 During the tour uplink is typically performed at 500 bps. The confidence level for uplink transmission is 99% or better. Generally speaking, the uplink signal is much stronger due to the much higher radiating power of the ground antenna Playback During cruise, telemetry is returned to the ground according to the (often limited) downlink capability, and is generally not heavily optimized due in part to a limited set of telemetry modes and tour capabilities which are still in development. During tour, however, much effort has been spent in selecting the data rates and DSN pass configurations to maximize the data return related to the project s primary science objectives. For the purposes of operational simplicity, the Tour DSN coverage has been classified into two categories: "high activity," presumably when the science opportunities are most intensive and require the most data to be collected, and "low activity," when the opportunities are more scarce or permit low data return. The science community has indicated that 1.0 Gbit per day for low activity periods and 4.0 Gbit per day for the high activity periods is adequate to achieve their science goals. To accomplish this, high activity periods are concentrated at targeted flybys and Saturn periapses, and take up about one quarter to one third of each orbit. These passes are 9 hours in length and use a northern-hemisphere 70 meter station or 70/34 array. Communications is 2- way coherent at a 90% confidence level with ranging on. Low activity passes are also 9 hours in length and use northern hemishere 34 meter stations. Communications is also 2-way coherent at a 90% confidence level, ranging on. During the tour, expected data rates for the spacecraft's HGA and 19W X-band transmitter range from 14 kbps to 166 kbps. These rates vary due to the assumed telecom confidence level, the ground station configuration and the Earth's motion around the Sun, which affects the transmission range, and Saturn's motion around the Sun, which affects the declination of the spacecraft as seen from Earth. Earth's motion is by far the dominant geometric factor and is evident in the sinusoidal nature of the link performance. Since the link performance varies significantly with time, multiple data rates must be used as the performance changes or significant data return capability will be lost. In addition, the performance varies during a pass and multiple data rates per pass also increases telecom performance significantly as show in figure Data Rate Telemetry Pass Ratio of Time Used 1/6 2/3 1/6 Figure 2.20 Multiple Data Rate Strategy Time Fourteen data rates compatible with the spacecraft information system have been chosen for the tour as listed in Table 4. These rates cover all expected ground apertures with a minimum of lost data return capability. Higher rates of and kbps are available, but are not used because either they cannot be supported by the telecom link or because they are not needed to achieve the 4.0 Gbit daily return. Any slot that would be occupied by a high data rate would be better applied towards the lower data rate region to increase performance during low activity days. 2-22

67 Table 2.3 Tour Data Rates (kb/s) If a DSN pass is lost too late in the planning or execution process to alter the sequence safely, no steps will be taken to recover the data recorded on the SSR and the sequence is allowed to proceed as planned. The spacecraft continues operation as if the data are being received successfully, resulting in loss of these data as they are overwritten during the downlink period and the following observing period. The following figures show the downlink science data return in Gbit over the tour for Goldstone, Madrid, and Canberra (occasional Canberra passes may be required to resolve DSN conflicts). Nine hour passes are assumed, causing the jagged data returns, especially for arrayed antennas, since occasionally the top two data rates are not available for a full 9 hours, and occasionally the lower data rate is used less than the minimum of 45 minutes. In these cases, additional data return could be achieved by lengthening the duration of the pass beyond 9 hours, or reducing the time you collect data in the highest rate. Note that there are periods when 4 Gb of science is not achievable even at arrayed stations, ant there are periods of low activity when 1 Gb is not available from 34 m HEF antennas DSN Lockup DSN lockup during tour is theoretically predicted to be on the order of seconds; however, during cruise lockup has typically taken several minutes. In order to prevent data loss, the playback of data at the beginning of a pass (as well as during data rate or coherency changes) should be avoided. During cruise, the technique for preventing data loss is to snap and restore the pointer after 15 minutes of playback to the start of the partition. This duplicates the playback of the first 15 minutes of data and accommodates an equivalent lockup time. The tour flight software has implemented a playback pause capability which halts SSR playback for a fixed amount of time whenever a new telemetry mode is activated. This time can be uploaded as a parameter and can be used to accommodate DSN lockup, data rate, or coherency changes. During playback pause, the transmitter still sends data to the ground at the expected rate, but only real-time engineering and fill frames; no data from the SSR is sent to the ground. For tour, 5 minutes of lockup and 1 minute of pause at each data rate are the baseline Maintenance Preventive Maintenance (PM) is scheduled to occur during weekly maintenance downtimes. The major goal of PM is to minimize the likelihood of a sudden loss of an asset requiring corrective maintenance. The maintenance teams perform hundreds of maintenance procedures each month on the antennas. Most of these can only be conducted during daylight hours during the standard workweek (M-F at CDSCC & GDSCC, Tu-F at MDSCC). Typically, each 26-meter, BWG, HEF, and HSB antenna is taken down for maintenance for a 6-8 hour period each week. It is not uncommon for maintenance time to be reduced on these antennas to as low as 4 hours in a week when special support is requested by a flight project. The 70-meter antennas are taken down for maintenance 8-16 hours each week, depending on the complex. When one 70-meter antenna is down for an extended period of time because of an implementation, the maintenance hours are reduced on the other two 70-meter antennas. It is extremely rare for maintenance to be reduced by more than 50%. 2-23

68 5000 Bits to Ground - Goldstone ARR MET ARR BWG HEF Jul 2004-Dec 2005-Jul 2006-Jan 2006-Jul 2007-Jan 2007-Jul 2008-Jan 2008-Jul

69 5000 Bits to Ground - Madrid ARR MET ARR BWG HEF Jul 2004-Dec 2005-Jul 2006-Jan 2006-Jul 2007-Jan 2007-Jul 2008-Jan 2008-Jul

70 3500 Bits to Ground - Canberra MET ARR 1000 HEF 500 BWG Jul 2004-Dec 2005-Jul 2006-Jan 2006-Jul 2007-Jan 2007-Jul 2008-Jan 2008-Jul

71 The project policy is to adhere to weekly maintenance requirements whenever possible, especially during implementation. An attempt to waive maintenance will only be pursued in the most extreme cases where maintenance degrades high value science and all other avenues have been exhausted Probe Relay Problem The receivers in the Huygens Probe support equipment on board the Cassini spacecraft have exhibited a performance anomaly under the conditions expected during the nominal Probe mission. There is sufficient margin to maintain both carrier and sub-carrier lock throughout the Probe mission. However, at the link levels expected, the digital circuitry which decodes the data from the sub-carrier does not have sufficient bandwidth to properly process the data from a sub-carrier which has been Doppler shifted by the nominal 5.6 km/s velocity difference between the Cassini orbiter and the Huygens Probe. The initial assessment of the affect of this anomaly is that it will lead to unacceptable data losses during the Probe descent to Titan. This anomaly was addressed by redesigning the orbiter trajectory at the time of the probe mission in order to minimize the Doppler on the received probe signal. In addition to this, it may be possible to preheat the probe transmitters for four hours before the probe mission to improve data performance and to insert zero packets into the probe data stream minimizing the expected cycle slips. However these latter two options are still being investigated. 2.5 Data Routing and Storage Data control on board the spacecraft is controlled by the Command and Data Subsystem (CDS) which controls two Solid State Recorders (SSRs). Cassini s two SSRs are the primary memory storage and retrieval devices for the orbiter. Each SSR contains 128 submodules, of which 8 are used for flight software and 120 are useable for telemetry. Each submodule has 16,777,200 bits for data, so the total data available for telemetry for each SSR is Gbit. Expressed in terms of 8800-bit telemetry frames, this is 228,780 frames per SSR. Accounting for effects of solar and cosmic radiation, the end of mission capacity is expected to be no less than Gbit per SSR. There are currently no bad blocks on either SSR, so the total start of mission capacity is still available. Spacecraft telemetry and AACS, CDS, and instrument memory loads can be stored in separate files, or partitions, on board the SSR routed through virtual channels. Three telemetry partitions have been defined on each SSR, numbered 4, 5 and 6. Partition 4 is the general science partition, whereas partition 6 is for engineering data. Partition 5 is used to store optical navigation images. In order to support science both the AACS prime engineering packets and the RFS packets are duplicated and recorded to Partition 4 for downlink to ground. There are three different SSR modes in which the SSR can function: Read-Write to End, Circular FIFO, and Ring Buffer. There is also a record pointer and a playback pointer, which mark the memory addresses at which the SSR will write or read, respectively. In Read-Write to End, there is a logical beginning and end to the SSR. Recording begins at this logical beginning and continues until either the SSR is reset (the record and playback pointers are returned to the logical beginning) or until the record pointer reaches the end. If the record pointer does reach the end, recording is halted until the SSR is reset. In Circular FIFO, there is no logical end to the SSR. The data is continuously recorded until the record pointer reaches the playback pointer. The Ring Buffer mode behaves exactly like Circular FIFO, with one exception. Recording will not stop if the record pointer reaches the playback pointer. The principal purpose of the Solid State Recorders (SSRs) is to store science and engineering data during observation periods for playback during DSN passes, and to buffer FPW and engineering data during DSN passes for downlink during those same passes. The amount of 2-27

72 data which can be recorded per period is primarily limited by the downlink capability of DSN stations. During most of cruise, only one SSR is needed primarily for engineering, but also to record maintenance, calibration, and checkout data, as well as limited cruise science. The other SSR may be turned off. During approach and tour, however, both SSRs are on. Even though a majority of days during tour are expected to be low activity, requiring only one SSR, both SSRs are kept on to maintain a 4.0 Gbit storage and downlink capacity. Activity levels change several times per orbit, and cycling the SSRs on and off increases the ground workload and may impact the reliability of the SSRs. Each CDS is attached to the two SSRs such that each CDS can communicate (read, write) with one SSR or the other SSR but not simultaneously. The ground has the capability to control how the SSR attachments are configured via real-time command or a stored sequence. Under fault response conditions FSW can switch SSR attachment from CDS A to CDS B. The CDS receives the uplink command stream via the RFS and decodes this stream which includes timing (immediate or sequence), routing, action, and parameter information. The CDS then distributes commands designated for other subsystems or instruments, executes those commands which are decoded as CDS commands, and stores sequence commands for later execution. The CDS has a capacity of 153,600 words. One CDS word equals 16 bits. The following table shows the allocation for the CDS words. Table 2.4 CDS Words Allocations Sequence Memory CDS Words On-board modules 12,288 Background sequence 111,808 Live Movable Blocks 10,240 TCM 2,048 IVP Update 10,240 Mini-sequence 4,096 IDAPs 1,856 Global Variables 1,024 Total: 153,600 The CDS receives data destined for the ground on the data bus from other on-board subsystems, processes it, formats it for telemetry and delivers it to RFS for transmission to Earth. Each subsystem interfaces with the data bus through a standard Bus Interface Unit (BIU) or a Remote Engineering Unit (REU). Data is collected in bit frames, and Reed- Soloman Encoded on downlink. A 32 framesync marker along with the encoding increases these frames to 10,112 bits. CDS software contains algorithms that provide protection for the spacecraft and the mission in the event of a fault. Fault protection software ensures that, in the case of a serious fault, the spacecraft will be placed into a safe, stable, commandable state (without ground intervention) for a period of at least two weeks to give the ground time to solve the problem and send the spacecraft a new command sequence. It also autonomously responds to a predefined set of faults needing immediate action Orbiter Telemetry Modes A set of telemetry modes has been defined to accommodate different engineering and science activities and the changing telecommunications capability during the Cassini mission. Eleven telemetry modes were implemented before launch to accommodate pre-launch and early postlaunch operations. The remaining modes are being developed and tested during cruise. Thirty modes can be stored on-board the spacecraft at any one time; more may exist on the 2-28

73 ground, and various modes may be updated or replaced as the telemetry needs of the mission change. Refer to CAS for more information on orbiter telemetry modes. Each telemetry mode represents a unique configuration of data sources, rates, and destinations for telemetry data gathered and distributed by the CDS. Data are routed either to the SSR for temporary storage or to the RFS for transmission to the ground or both. There are five sources of telemetry data: 1) Engineering data from the spacecraft subsystems is gathered in every telemetry mode and sent to the SSR for recording. Realtime engineering data are also included in the downlink data stream in most of the telemetry modes. For some of the telemetry modes used during the early part of the cruise phase, when the downlink data are transmitted via the LGAs, the engineering data rate could drop to 0 or 20 bps for SSR playback and 20 bps in real-time. 2) Science housekeeping data are gathered from the instruments when they are operating and are either sent to the SSR or routed into the downlink data stream. The peak rate for science housekeeping data are predicted to not exceed 275 bps. 3) Scientific data from the instruments is always routed to the SSR in the telemetry modes that include science data collection. Data rates in these modes can be up to 410 kbps, however, the actual data rate into the SSR during science data collection in a given telemetry mode can vary up to this maximum. This is because there is insufficient storage and downlink data volume to collect data continuously at this rate, and some of the higher rate instruments will have to vary their data collection rates to fit within the available downlink data volume. 4) Playback data from the SSR is routed into the downlink data stream to the RFS, at speeds depending on the downlink data rate. 5) Probe data are included in two of the telemetry modes to allow for Probe checkout and Probe relay operations. These data will be collected at a rate of about 20 kbps. Tables 6-7 describes the telemetry modes used for tour, which have been grouped into functional categories, which are: Realtime Engineering (RTE) Probe Checkout (PCHK) Probe Operations (PRLY) Science and Engineering Record (S&ER) Realtime Engineering plus Science Playback (RTE&SPB) SAF Instrument Checkout (SAF) 2-29

74 Telemetry Mode TELEMETRY MODES - RECORD & REAL-TIME DOWNLINK C A P S C D A I N M S M A G RECORD TO SSR DOWNLINK SCIENCE HOUSEKEEPING ENG ENG ENG TOTAL M R C U V R C I M R C I I U V R I I P C M P Total P4 P6 I P I V I A A N I P I S S V I A Downlink S S S D A S rate Rate Rate (bps) M W R I M D P M M W R S S I M D (bps) S S A A G A (bps) (bps) (bps) I S S S S A S S I S S n w S S R S&ER S&ER S&ER S&ER S&ER S&ER-5a S&ER S&ER S&ER S&ER-10 (prime)* S&ER-10 (online)* RTE RTE RTE RTE PCHK PRLY (prime) PRLY (online) * S&ER-10 is the telemetry mode used during SOI.

75 Telemetry Mode C A P C D A I N M M A G TELEMETRY MODES - PLAYBACK RECORD TO SSR DOWNLINK SCIENCE ENG SSR HOUSEKEEPING ENG TOTAL M I M R P W C I R I S S I S S U V I V I M R A D P S A (bps) Playback (bps) C A P C D A I N M M A G M I M R P W C I R I S S I S S U V I V I M R A D P S A Total rate (bps) R-T ENG (bps) Downlink (bps) RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB RTE&SPB SAF SAF (2)

76 2.5.2 SSR Usage Partitions 0-3 on each SSR are memory load partitions containing flight software. Each SSR can have up to 3 additional partitions used for telemetry. A CDS command edits partitions in the background sequence, enabling the number and size of telemetry partitions to be changed on a daily basis if needed. The minimum size of a partition in order for it to exist is one frame, or 8800 bits. The exception is the recording of Huygens data, which is duplicated on each SSR using a unique partitioning strategy. During cruise, typically one SSR with a single telemetry partition in circular FIFO mode is used to store and downlink all data collected, mixing engineering, housekeeping, maintenance, checkout and science data collected. Engineering is recorded continuously at a rate of 1638 bps. At this rate, one SSR can store up to 14 days of data (assuming a capacity of 2.0 Gbit). During cruise, the least frequent DSN passes occur once per week. The SSR therefore would record up to 7 days of data between the least frequent downlinks, filling half of its capacity. During a DSN pass at greater than 20 bps downlink rate, along with real-time engineering, selected data from the SSR can be played back if desired. At 20 bps (the minimum planned downlink rate) only real-time engineering can be sent to Earth. At the end of the pass, the pointers are not reset and the SSR continues to record where it left off. Figure 2.24 Cruise One-Partition SSR Management When a fault has occurred, at least 7 days (which is also the maximum time between passes) of data collection is guaranteed. This strategy allows time for the ground to make arrangements to receive fault protection data and engineering data before or after the fault to analyze the problem. If the spacecraft is not directed otherwise, it stops recording data once the record pointer hits the playback pointer. During the later portion of cruise and tour, once the final flight software is uploaded, the SSRs are configured to use multiple partitions. Engineering data, optical navigation images, and/or high value science data can be routed to specific partitions and preserved separate from general science data for priority or multiple playbacks. For tour, partition 4 is used as the primary day-to-day telemetry partition. Engineering data stored during observation periods does not need to be downlinked every day, so it is routed to partition 6 at 1638 bps. Some engineering, however, is required to reconstruct pointing, etc., and this data is duplicated in partition 4 during observation periods at a lower rate of 724 bps. 2-32

77 LOW ACTIVITY DAY (1 SSR) A4 PR SCI + AACS A5 A6 PR OP NAV PR CIRC FIFO START EMPTY A4 = science partition with duplicated subset of engineering data (e.g. AACS, RFS) required for playback. Circular FIFO allows free recording up to data played back and is required if any data is to be held over to next pass. A5 = OPNAV partition. Circular FIFO allows for MAPS data to use up OPNAV space after playback. Sized to volume of contents plus playback buffer for data recorded in A5 for each downlink Mb each OPNAV (484 frames) which assumes compression of 4:1 or better (>7:1 performance has been observed in flight on OPNAV-like images). CIRC FIFO ENG RING BUFFER A6 = engineering partition. Sized to hold 39.5 hours, needed for anomaly recovery. Ring buffer allows engineering to be recorded without pointer management. After safing, fault protection may route post-fault engineering to A4. A4 P A5 P RECORD R OP NAV All engineering in A6 at 1623 bps and science & a duplicated subset of engineering in A4 at 718 bps, plus HK at up to 239 bps. OPNAVs are routed to A5 by telemetry mode overlay command. R SCI + AACS A6 ENG R A4 A5 PLAYBACK R P SCI + AACS R P A6 OP NAV P 1 In order as shown. A6 is never played back unless needed for anomaly diagnosis. All data collected during playback (including ENG at 1623 bps) must be recorded in active partition ONLY. Therefore, playback buffer in A5 must be bookkept for each downlink as illustrated to prevent data loss. Playback pointer is paused at start of downlink and at data rate changes for DSN lockup; record pointer is free to continue. 2 ENG POST-PLAYBACK Resize partitions if needed (and no carryover). Reset partition 4 and 5 pointers to start of partition. R D. Seal 10 May 2002

78 HIGH ACTIVITY DAY (2 SSRs) A4 PR A5 PR B4 PR B5 PR START EMPTY SCI + AACS A6 OP NAV PR ENG SCI + AACS B6 OP NAV PR ENG Parition map for each SSR must always be identical in case of unexpected SSR swaps. Also, size partitions on each SSR to equal volumes whenever possible for ops simplicity. Stochastic compression or unforseen problems makes SSR swaps variable, so A5 or B5 must be able to contain entire volume of OPNAVs (plus playback buffers). Paying twice in storage capacity only limits science if SSRs would otherwise be completely filled; this is unlikely since OPNAVs will almost always be recorded on low activity days. A4 RP A5 P B4 P B5 P RECORD SCI + AACS A6 OP NAV P R R SCI + AACS B6 OP NAV P R SSR swap is triggered when one identified partition becomes full. This partition should always be A4/B4. If A5/B5 are sized to each contain the full volume of OPNAVs (plus playback buffers), they will never fill up before the swap. Otherwise, data will be discarded. ENG R ENG R A4 PR A5 B4 B5 PLAYBACK SCI + AACS R A6 OP NAV P P ENG 1 R R P SCI + AACS 3 4 B6 OP NAV P ENG 2 P R R In order as shown. If A5/B5 are not used, the record pointers and playback pointers will be at partition start and the partition will just be skipped. High-rate MAPS data collection must wait until after start of A4 playback so there will be SSR space for the data. Pause of playback pointer for DSN lockup occurs before playback order is asserted, so downlink starts on last partition B4 with room to record and only switches to filled A4 when playback resumes. POST-PLAYBACK Note: the1-ssr strategy can be implemented identical to this one; some partitions would just not be used. Only day-to-day variations in OPNAV volume require special handling. Resize partitions if needed (and no carryover). Reset partition 4 and 5 pointers to start of partition. D. Seal 10 May 2002

79 2 LOW ACTIVITY DAYS (1 SSR) WITH CARRYOVER A4 PR A5 PR START EMPTY A4 A5 POST-PLAYBACK SCI + AACS A6 OP NAV PR CIRC FIFO As usual: A4 = science + some engineering. A5 = OPNAVS. A6 = all engineering. R SCI + AACS R A6 OP NAV P P Usual is reset pointers in partitions 4 & 5. If carryover, do not reset any pointers. This is the only change in operations needed to acommodate carryover! CIRC FIFO ENG RING BUFFER P ENG R A4 P A5 P RECORD #1 A4 A5 RECORD #2 R SCI + AACS A6 OP NAV P R As usual, record pointers move ahead. SCI + AACS R R A6 OP NAV P P As usual. Data carried over in A4 + new data recorded must not exceed partition capacity (of A4 + B4, really). ENG R ENG P R R A4 P SCI + AACS 2 A5 R A6 OP NAV P P ENG R 1 PLAYBACK #1 As usual, in order shown, except data left on A4. Downlink capability must be adequate to downlink all of A5. All data recorded during downlink is stored in active partition as usual. A4 SCI + AACS 2 P A5 R P R A6 R OP NAV P ENG 1 PLAYBACK #2 As usual, in order shown. All data on A4 & A5 downlinked. POST-PLAYBACK Resize partitions if needed. Reset partition 4 and 5 pointers to start of partition. D. Seal 10 May 2002

80 Partition 6 is sized to hold 25,596 frames of engineering data (225 Mbit). This size guarantees that no engineering data is overwritten as long as there is one pass per day (at any complex). If passes are skipped, the duration of recording to any one SSR must not exceed 39.5 hours over two consecutive observations periods in order for engineering data to be preserved for fault diagnosis. For example, if both SSRs are filled at an even rate during a 48-hour observation period, each SSR is only used for 24 hours. If the subsequent observation period only uses one SSR, and the duration of that observation period exceeds 15.5 hours, some engineering data may be unrecoverable if a fault should occur during these two days. Note that the size of partitions 4 and 6 total 2013 Mbit, the total volume on each SSR usable for telemetry. Partition 5 is set aside for optical navigation. This data is routed via a telemetry mode overlay command. Once the OPNAV data is complete, an additional telemetry mode overlay command is sent to restore the data flow to its original form. New telemetry modes for each permutation of data routing are not required; the overlay command is sufficient to reroute specific instrument s data to the appropriate partition. If partition 5 is used, its volume must be taken from partition4. OPNAVs are taken with the ISS NAC, using lossless compression and no encoding. ach NAC file is 1027 rows x 1036 columns x 16 bits (the first three rows, and the first 12 columns of all subsequent rows contain header data). Therefore, the maximum file size for these images is 17.0 Mbit. Recent in-flight performance of the lossless compressor on OPNAV-like images has been estimated at over 7:1. Refer to the guidelines & constraints in section 8 for some details on how SSR management is implemented. Table 2.7 Tour SSR Partitioning # FUNCTION SIZE 0 DEFAULT MEM. LOAD 1 30 Mbit 1 DEFAULT MEM. LOAD 2 30 Mbit 2 NEW MEMORY LOAD 1 30 Mbit 3 NEW MEMORY LOAD 2 30 Mbit 4 TELEMETRY (SCIENCE & ENGINEERING) 1788 Mbit 5 TELEMETRY (OPNAVS FOR TOUR ONLY) 0 unless needed (tour only) 6 TELEMETRY (ENGINEERING FOR TOUR ONLY) 225 Mbit (tour only) During downlink, all data recorded can only be written to the active partition being played back. This is required in order for the CDS to retrieve data from the SSR as quickly as possible (i.e. from only one partition at a time) to support the high downlink rates during playback. When more than one SSR is required (e.g. high activity day), data recording will switch from one SSR to the other only when partition 4 becomes full. The sizing of the other partitions, if used, should be done to ensure that they do not fill up before partition 4 (or data will be lost). Optimizing partition sizing should be avoided whenever possible to minimize operations complexity; instead, partitions should be sized the same on each SSR and with sufficient margin to allow for stochastic data collection Data policing The limitations on downlink capability and SSR volume, as well as the non-deterministic nature of many of the instruments' data collection rates implies the need for control over the amount of data each instrument can place on the SSR. Data volume is set aside each day for OPNAVs, when needed, and engineering, and whatever remains of the downlink capability can be determined and allocated among the science instruments. The science office determines the allocation process and assigns volume on a per-instrument basis as a function of time, including instrument housekeeping data. Once these allocations are uploaded to the 2-36

81 spacecraft, they are activated in a background sequence when observations start, and are then enforced by CDS. The CDS is responsible for protection of instrument data and ceases to record data from an instrument which has exceeded its allocation. Navigation OPNAVs, when taken, are implemented as supplements to the ISS data allocation. The CDS has room for 90 data allocation tables, allowing for 44 days of SSR management with one uplink of these tables. (Separate tables are used for both observation and downlink periods, and two tables are set aside for support imaging and OPNAVs.) Carryover During low-activity periods, there will occasionally be a need to collect more data than can be downlinked in a single low-activity pass. This option is desirable during extended low-activity periods when prime science opportunities are unevenly spaced. The amount of data which can be taken during the observation period immediately preceding a given downlink period is usually assumed to be equal to the downlink capability of the pass minus the FPW and engineering data collected during the pass (after accounting for R-S encoding). However, if it is desirable to take more data during a particular observing period, this can be done by borrowing data from subsequent observing period(s). The total amount of data which can be taken over these multiple observing periods is still fixed, and limited to the total capability of the multiple downlink periods minus the FPW and engineering data collected during those downlink periods. Data storage must meet two key requirements: data collected during observations periods must not exceed the volume that the SSR can store, and data collected during the observation + downlink period that is intended for playback must not exceed the downlink capability of the DSN pass (unless data is carried over). 2.6 Navigation and maneuvers The main objective of navigation is to maintain the spacecraft on the planned trajectory for the duration of the nominal mission. Secondary objectives of the navigation effort include minimizing the operational complexity of its related activities and the delta-vee required to maintain the correct trajectory. Unlike other missions, the trajectory design will not be reoptimized continuously. Every effort will be made to maintain that trajectory and not replan a new path. While Cassini is in the inner solar system, the focus is on achieving the three planetary flybys and satisfying the Earth swingby requirements. The Earth impact probability, required to be less than one in a million, is controlled by biasing the trajectory away from the Earth until the final pre-earth maneuver. After the Earth flyby, the long Earth to Jupiter and Jupiter to Saturn legs are rather uneventful. During the Saturn approach phase, the nav team calibrates and understands the optical portion of the navigation system and places the spacecraft on the proper trajectory for the Phoebe encounter and SOI. In tour, the nav system controls the spacecraft trajectory on the nominal tour, and updates the tour trajectory only to account for expected variations in parameters such as satellite ephemerides and the Titan atmospheric density. Also during tour, the nav team is responsible for providing accurate predicted and reconstructed spacecraft and satellite ephemerides Tracking Navigation primarily uses DSN tracking during cruise and tour to collect two separate types of tracking data as follows. Ranging is derived from a modulation on the uplink which is processed by the spacecraft and remodulated onto the downlink carrier. The ranging channel competes with the telemetry channel for power and in intervals of low telecom performance, telemetry modulation must be turned off in order to achieve satisfactory ranging performance. 2-37

82 Coherent Doppler requires a 2-way coherent X-band link and is a measure of the total frequency shift of the up- and downlink carriers. The spacecraft receives the carrier from the ground and multiplies that frequency by a fixed ratio to derive the downlink carrier frequency. In addition to DSN tracking, optical navigation is used during approach and tour and provides a measurement of a satellite against a fixed stellar background. The images taken by the imaging cameras directly support the estimation of not only the Cassini spacecraft ephemeris but also the positions of the satellites, particularly early in the tour. OPNAVs complement the radiometric doppler and ranging measurements in orbit determination. Operational measurements begin during Saturn approach and continue throughout the duration of the mission, but are needed less often after the first year of the tour. Initially, between 4 and 8 images per day are taken for the first few Titan flybys with the number of images decreasing as the ephemerides converge. The number of images increase when approaching icy satellites for the first time. During the first two years of the mission, DSN tracking can always obtain the Doppler data, but obtaining the ranging data is complicated by a number of competing requirements. The spacecraft is normally sun pointed which requires that the communications be accomplished using the low gain antennas (LGAs). The performance characteristics of the LGAs create problems with the acquisition of range data. Navigation requires Doppler and ranging data from both northern and southern hemisphere tracking stations. The spacecraft analysis team requires telemetry at least once per week. During this portion of early cruise, there are several periods where telemetry both types of tracking data are not achievable and must be accounted for. During later cruise, the spacecraft geometry is changing more slowly and HGA communication is possible. Tracking 1-2 times per week is sufficient to maintain acceptable knowledge of the spacecraft trajectory. On the long Jupiter-Saturn leg (the quiet and science cruise phases), orbit determination is only needed on a quarterly basis. During tour, most navigation tracking is tied to the schedule of close satellite encounters. Preencounter tracking in part supports the flyby targeting maneuver which places the spacecraft in the final flyby trajectory. Post-encounter maneuvers are required only for Titan as a result of its gravitational effect on the trajectory. Since the nominal DSN coverage is one pass per day during tour, tracking that rides along whenever these passes are desired by science may be acceptable. For optical navigation during approach and tour, once the overall requirements for optical navigation are known, a super set of opportunities is generated that pass all of the pointing and timing constraints. Each opportunity is a unique image and specifies the time of the image, its target (typically a star) and the satellite also being imaged. The super set contains extra images (e.g. 25%) in order to allow flexibility in the science planning process. Requests for OPNAVs are submitted through the Cassini Information Management System (CIMS) as engineering activities. The narrow angle camera is the primary instrument for OPNAVs although the wide angle camera can also be used. Navigation then participates in the planning process and is responsible for assuring that the images approved in the final sequence meet the nav requirements, and that the details of each observation start/end times, turns, camera parameters, etc. are properly included. Pointing constraints are checked and ride-alongs are coordinated. The real-time execution of the OPNAVs is monitored and the images are acquired at the beginning of the next downlink pass for processing. 2-38

83 2.6.2 Maneuvers During the inner solar system cruise, typically three maneuvers are required between consecutive encounters; the first to clean up the dispersions caused by the first flyby, and the next two to assure accurate delivery to the next encounter. In the later portions of cruise, the trajectory requires very infrequent maneuvers. However, flushing maneuvers of at least 5 seconds in duration are required to flush the wet portion of the propellant valves of the main engine every 400 days. To maintain at least one maneuver every 400 days, several maneuvers have been added to the schedule and are accommodated in the navigation plan. These flushing maneuvers ensure that oxidization of iron alloys in the bipropellant feed system do not build up long enough to plug the small orifices of the valves. Maneuvers have two components of delta-vee: a deterministic (or pre-planned) component, and a statistical component required to clean up dispersions to maintain the correct trajectory. Cassini can execute maneuvers using either the main engines or the Reaction Control System (RCS) thrusters. Generally, delta-vees larger than a crossover point, currently at 0.5 m/s, are done with the main engine since the main engines have a higher thrust than the RCS thrusters and can impart higher V in a shorter period of time. The crossover point is selected within limits to share the delta-vee burden between the bipropellant and monopropellant systems and to take advantage of the improved accuracy with the RCS. Ideally, Cassini should run out of each propellant at the same time in the extended mission (save for any hydrazine left over for continued attitude control). Main engine maneuvers require REA heaters on for 6 hours before the burn (from TCM 18 onward). During each main engine burn, the main engine nozzle gimbals control the engine to apply thrust as closely as possible in the direction of the center of mass of the spacecraft. The EGAs are stowed in the same position every time. For each main-engine maneuver that occurs near the ring plane, the MEA cover must also be opened before the maneuver and closed afterward in order to minimize micrometeoroid exposure of the sensitive engine nozzles. The maneuver will not proceed unless this is verified on the ground and a go command is sent to execute the maneuver block. The cover is closed after the engine burn, following an appropriate cooling period. The total open time is usually six to seven hours per main engine maneuver. Both types of burns must be at least one second in duration; the minimum resolution for a main engine burn is 8-12 cm/s. During cruise, all maneuvers have continuous coverage for three DSN passes centered on the burn. The SSR will record maneuver data during the time the spacecraft is off-sun (or off-earth for TCM 18 onward). During early cruise where HGA communication is not possible, up to seven passes at 40 bps downlink (20 bps SSR playback) are required to play back all recorded TCM data. As a result, only the off-sun data is played back (off-earth for TCM 18 onward). Sprint turns may be used when they are necessary to meet the thermal constraints. A sprint turn to the burn attitude can take as long as 7 minutes each way. The total off-sun time for a burn includes the turn to the burn attitude, a settling period of approximately 5 minutes, the actual burn time, a burn settling of 2 minutes, and the turn back to Sun-point. During cruise, maneuver backup dates are typically 14 days after the scheduled maneuver when time allows. Beginning with TCM 19a, in September 2003, RCS TCM turns to and from the burn attitude will be done on reaction wheels. Control during the RCS TCM burns will still be on RCS but the RWAs will be left ON during the burn in their RATE mode. For ME TCMs, RWAs are used for the roll turns, RCS for the yaw turns. RWAs are OFF during the actual ME burn, then turned back ON afterward. This operational strategy will save significant hydrazine. The tour selected for the Cassini mission places new and significant requirements on the execution of maneuvers. Control of the trajectory requires at least three maneuvers be scheduled between each targeted encounter of Titan or an icy satellite. The scheduled dates, as follows, were chosen to balance the V budget with operational constraints on placing maneuvers close to flybys. 2-39

84 Encounter Cleanup - scheduled at each targeted Titan encounter + 3 days. This maneuver corrects for most errors in the flyby and may provide some or all of the changes required to achieve the next flyby. Generally these are statistical maneuvers. Near Apoapsis - scheduled near apoapsis on the orbit between the targeted encounters. This maneuver sets up the trajectory to achieve the next targeted encounter. In many cases this maneuver has a significant deterministic component. Approach Targeting scheduled at each targeted encounter 3 days. This maneuver is statistical and cleans up any residual errors from the apoapsis maneuver in order to achieve an accurate delivery to the next encounter. In order to maintain the spacecraft on the tour within the available propellant, it is necessary to execute both the cleanup maneuver and the near-apoapsis maneuver. The maneuvers may be delayed by a day or two with only a modest increase in the propellant cost, but skipping a maneuver could required a tour redesign due to propellant availability. The criticality of the approach targeting maneuvers depends upon the achieved accuracy of the near apoapsis maneuver. Also, the reference tour includes a significant number of 16 day orbits. With only 16 days between targeted encounters, a maneuver must be accomplished, on average, every 5.3 days. This maneuver frequency implies that maneuvers can occur on any day of the week and at any time of day. With only a few days between maneuvers, the time to evaluate the results of a maneuver, determine the post-maneuver trajectory and plan the next maneuver is at premium. With more than 160 TCMs planned for the tour, efficient and consistent planning and execution is necessary. All maneuvers will be executed during a single DSN tracking pass with the maneuver minisequence uplinked twice at the beginning of the pass. If, because of DSN problems at the beginning of the OTM pass, either 1) the health status of the spacecraft cannot be verified, or 2) the maneuver cannot be successfully uplinked there is insufficient time to retry the maneuver and the backup pass must be used. In this case, the OD solution will not be recalculated, but the maneuver will simply be replanned for the following day using the same trajectory. Two-way Doppler tracking data is collected before and after the maneuver (in general 2-way tracking will be lost during the maneuver). The engineering telemetry recorded during the maneuver is played back immediately after the maneuver. For icy satellite flybys, targeting maneuvers before the flyby are also required but typically cleanup maneuvers after the encounter are not required, since the satellite s gravitational effect on the trajectory is negligible. Occasionally there are maneuvers scheduled on the day after icy satellite flybys. These maneuvers are primarily deterministic and are implemented as canned maneuvers. The maneuver parameters and mini-sequence is automatically generated by the Maneuver Team. This team has the responsibility for generation of the final orbit determination solution, generation and validation of the mini-sequence and transmission of the command file to the ACE for uplink. The generation and validation of the input files and parameters necessary for the execution of the automatic maneuver generation software is usually accomplished during standard working hours. A typical maneuver timeline is shown in the following figure. In addition, requirements for handover passes (two-station passes) are given for maneuver support. 2-40

85 Example Nine Hour OTM Pass Spacecraft Event Op Mode transition 6 hours DFWP-TCM, Spin Maneuver block* off-earth DFWP-TCM No Spin Op Mode transition 1:30 hr OWLT Earth Receive BOT A 9-hour OTM pass gives: > 1:41 hr hr for for verifying s/c health & safety and uplinking the maneuver > 7:33 hr hr science downlink! 2:20 hr hr two-way Doppler before and after maneuver min OTM engineering data playback EOT = Health & safety check + maneuver uplink = Two-way Doppler = Science downlink = Engineering downlink * = assuming worst case (longest) maneuver block length of 2:44 hr. 24 Apr 02

86 OTM Split-Pass Rules TWLT + 2:10 hr 1 BOT EOT Earliest Pass 1 2 REF X BOT TWLT + 2:10 hr 3 REF + 4 hr 1 EOT Latest Pre-maneuver two-way Pass 2 Ref * BOT TWLT + 2:10 hr 1 TWLT + 2:10 hr EOT 1 Earliest Postmaneuver two-way REF TWLT + 8:05 4 BOT EOT Latest 8:37 hr 5 * = Reference line. OWLT after beginning of 9-hour OTM window request in CIMS. = downlink only = one-way = two-way = three-way = transmitter on = transmitter off All All passes passes must must be be TWLT TWLT + 2:10 2:10 hr hr long. long Pass Pass 1 BOT BOT must must be be REF. REF Pass Pass 1 EOT EOT must must be be REF REF + 4:00 4:00 hr. hr Pass Pass 2 BOT BOT must must be be REF REF -- TWLT TWLT + 8:05 8:05 hr. hr Pass Pass 2 EOT EOT must must be be REF REF + 8:37 8:37 hr. hr.

87 RCS thrusters provide V for small maneuvers. For larger Vs, PMS has a primary and redundant pressure-regulated main rocket engine. Each engine is capable of a thrust of approximately 445 N when regulated. The bipropellant main engines burn nitrogen tetroxide (N 2 O 4 ) and monomethylhydrazine (N 2 H 3 CH 3 ) producing an expected specific impulse of up to 308s. These engines are gimbaled so that, under AACS control during burns, the thrust vector can be maintained through the shifting center of mass of the spacecraft. AACSprovided valve drivers for all the engines/thrusters operate in response to commands received from AACS via the CDS data bus. While the gimbals or the valve drive electronics are active -- be it during a burn or spacecraft checkout -- there is some effect to the Radio and Plasma Wave Spectrometer due to electromagnetic interference. Since maneuvers and checkout occur so infrequently, and usually during periods where little or no science is collected, this is not a problem, but RPWS planning staff must be aware of this. During a main engine burn, RCS thrusters, controlled by AACS, maintain the spacecraft attitude about the roll axis. The main rocket engine performs most large maneuvers with the pressure regulated; however, it performs maneuvers in the blowdown mode during portions of the mission when the pressurization system is pyro-isolated. Only one of the two main engines is permitted to operate at a time, whether pressurized or in blowdown mode. Mounted below the main engines is a retractable cover which is used during cruise to protect the main engines from micrometeoroids. The thin coating on the inside of the engines is especially vulnerable to micrometeoroid damage, and if this coating is damaged it can lead to the loss of the engine. The main engine cover can be extended and retracted multiple times (at least 25 times), and has a pyro ejection mechanism to jettison the cover should there be a mechanical problem with the cover that interferes with main engine operation. During cruise the cover will remain closed when the main engines are not in use Main Engine usage This subsection discusses main engine burn profiles for the Cassini mission set. V estimates are expressed in terms of mean V. The navigation staff recommends that suballocated V estimates be used for statistical maneuvers on a maneuver-to-maneuver basis. The suballocations are computed so that when added together, the net budget is equal to a 50% confidence ΔV estimate. However, this section considers the most realistic ΔV budget as a whole and therefore uses current best estimates. The launch delay to the tenth day of the primary launch period resulted in a near-optimal launch date and reduced the V requirements for reaching Saturn. Current estimates by the Navigation Team forecast the V available for the tour as 520 m/s from the bipropellant engines and 37 m/s from the monopropellant thrusters with a 95% confidence. An additional 70 m/s is held as end-of-mission margin. 2.7% of the bipropellant is considered unusable because it will be left over in the tank/lines and loading uncertainty. During testing, the MEA developed an oscillation (i.e., chugging ) when operated below certain pressure levels. In order to minimize the possibility of damage to the MEA or the spacecraft, the amount of time that the MEA is allowed to operate in the chugging regime will be limited to a total of 60 minutes. Figure 2.30 shows the predicted progression of the mean values of the bipropellant fuel and oxidizer pressures for the interplanetary portion of the mission. The circles on the figure denote the coast periods between events. The figure begins with TCM-1 which was accomplished in blow-down mode after the pressurization of the fuel and oxidizer tanks. The pressures before and after TCM-1 were obtained from telemetry data. Following TCM-1 the pressures varied as a results of helium absorption and temperature changes. TCM-2 was accomplished using the RCS thrusters and, therefore, is not reflected in the bipropellant pressure history. 2-43

88 Chugging Boundary 240 REA Operating Boundary DSM SOI 220 TCM 9 TCM Post-TCM-1 He Absorption Earth Swingby 180 Saturn Approach Fuel Tank Pressure, psia Figure 2.30 Biprop Tank Pressure History - Mean - Post-TCM-2 Trajectory Redesign The fuel and oxidizer tanks will be pressurized and regulated for the DSM. Following the DSM the oxidizer tank is isolated with a pyro valve and the fuel tank is isolated with a high pressure latch valve. Except for TCM-9, the plan is to remain isolated until just prior to SOI and accomplish all of the bipropellant maneuvers in "blow down mode. In order to preclude crossing the "chugging" boundary, it is necessary to pressurize the fuel tank during the execution of TCM-9. The history assumes that the fuel tank achieves the regulated pressure after the end of TCM-9 (the variations in the fuel pressure during the maneuver are not modeled). The figures assume that all maneuvers under 0.7 m/s are accomplished using the RCS system. (The actual value for choosing RCS or ME will be between 0.5 and 1.0 m/s). Regulator Leak Problem: As the initial pressurization was being performed just prior to TCM1, an unexpectedly high leak rate, 1700 sccm (standard cubic centimeters per minute), was noticed from the primary regulator (PR1). The specified rate for leakage from this regulator was supposed to be 0.6 sccm. High pressure latch valve LV10 was closed in response. The incident was addressed in ISA Z While regulator leakage is a well known phenomenon, the magnitude of this leak was surprising, especially given the leakage characteristics demonstrated by PR1 during ground testing. Analysis demonstrated that particulate contamination could very easily explain the observed regulator leakage, since the requisite particle size that causes a 1700 sccm leak is two orders of magnitude smaller than the filter capacity between pyro valve PV1 and PR1. That is, a particle that just fits and passes through the filter upstream of PR1 could actually cause a leak a hundred times larger than the leak observed at initial pressurization. Recommendation has been made to the project to continue to use PR1 unless the leakage reaches sccm. The PR1 regulation function is considered excellent despite high leakage 2-44

89 during DSM and TCM13, and procedures have been identified, specifically for the coordinated use of LV10, that can be employed at the next regulated maneuvers, Phoebe and SOI. 2.7 Attitude Control The Attitude and Articulation Control Subsystem (AACS) provides dynamic control of the spacecraft in rotation and translation. It provides fixed-target staring for HGA and remote sensing pointing and performs target relative pointing using inertial vector propagation as well as repetitive subroutines such as scans and mosaics. Rotational motion during the Saturn tour that requires high pointing stability is normally controlled by the three main Reaction Wheel Assemblies (RWAs), although modes requiring faster rates or accelerations may use thrusters. The additional fourth reaction wheel can articulate to replace any single failed wheel. Each RWA has a mass of kg. The largest reaction torque for each RWA is 0.13Nm. None of the three RWAs can absorb an angular momentum that is larger than 34Nms (approx rpm). All RWAs have their spin axes at o from the spacecraft Z-axis. Gyros are used primarily during the four year tour of the Saturnian system but will have some pre-saturn use as well. If, upon evaluation after SOI, the IRUs show no signs of performance degradation, they will be used continuously for the full tour. The IRUs will be re-evaluated whenever a life limiting characteristic becomes evident. In the event of IRU failure or loss of performance, IRU use during the tour can be restricted to periods of high science activity. AACS contains a suite of sensors that includes redundant Sun Sensor Assemblies (SSA), redundant Stellar Reference Units (SRU, also called star trackers), a Z-axis accelerometer, and two 3-axis gyro Inertial Reference Units (IRU). Each IRU consists of four gyros, three orthogonal to each other and the fourth skewed equidistant to the other three. AACS also controls actuators for the main rocket engine gimbals. With two redundant MIL-STD-1750A AACS Flight Computers (AFC) running flight software programmed in Ada, AACS processes commands from CDS via the CDS data bus and produces commands to be delivered to AACS actuators and/or PMS ME and RCS valves for spacecraft attitude and V control. AACS provides heartbeat, telemetry and fault response information to the CDS. For attitude control, PMS has a Reaction Control Subsystem (RCS) consisting of four thruster clusters mounted off the PMS core structure adjacent to the LEM at the base of the spacecraft. Each of the clusters contain 4 hydrazine thrusters. The thrusters are oriented to provide thrust along the spacecraft ±Y and -Z axes. RCS thrusters also provide V for small maneuvers. The approximate I SP for the RCS is 180s for turns, 140s for RWA unloads, 120s for limit cycling, and the theoretical max is 217s S/C Attitude Definition Table 2.8 Thruster Cluster Mass Properites Thruster Cluster # Mass (kg) Xcm (m) Ycm (m) Zcm (m) The spacecraft orientation in inertial space is always defined with respect to the basebody attitude. All changes to the attitude are referenced with respect to the basebody attitude. The base attitude is specified by defining two pairs of vectors; two local vectors in the S/C body coordinate system and two inertial vectors in the J2000 inertial system. From each of 2-45

90 these pairs, one of the vectors is termed the primary vector and the other is termed the secondary vector. Mission phase BOM Before SOI Before Probe Release After Probe Release EOM Table 2.9 Spacecraft Mass Properites S/C Information Mass X cm Y cm Z cm IXX IYY IZZ (kg) (m) (m) (m) (kg-m 2 ) (kg-m 2 ) (kg-m 2 ) Huygens attached, Mag boom stowed, RPWS antennas stowed. Huygens attached, Mag boom deployed, 2 RPWS antennas deployed. Huygens attached, Mag boom deployed, 2 RPWS antennas deployed. Huygens released, Mag boom deployed, 2 RPWS antennas deployed. Huygens released, Mag boom deployed, all RPWS antennas deployed. The base attitude shall be that attitude which satisfies the following two relationships: The primary body vector is pointing in the same direction as the primary inertial vector; The angle between the secondary body vector and the secondary inertial vector is minimized. Typically the primary body vector will be an instrument boresight and the primary inertial vector will be observation target. The secondary vectors are chosen to provide a preferertial attitude for satisfying (thermal) constraints or optimizing other aspects of the investigation. For example, the NAC boresight and the Z-axis could be the primary and secondary body vectors, respectively, while the S/C to Titan vector and the normal to the Titan flyby trajectory plane could be the primary and secondary inertial vectors, respectively. This would produce a continually changing attitude that points the NAC at Titan by rotating about the Z-axis. The "base" attitude is the spacecraft attitude that aligns one body vector with one inertial vector and places a second body vector as close as possible in alignment to a second inertial vector. The unit vectors X BASE, Y BASE and Z BASE are fixed in the base coordinate frame. The spacecraft X, Y and Z axes are parallel to X BASE, Y BASE and Z BASE, respectively, when the spacecraft is at the base attitude with zero offset. The user-selected body vectors must be members of the Body Vector Table (BVT). The user-selected inertial vectors must all be members of the Inertial Vector Table (IVT). If the chosen body vector does not exist in the BVT or the chosen inertial vector can not be constructed from entries in the IVT, the command to specify the base attitude is rejected. The base attitude is specified by the 7TARGET command. The 7TARGET command basically answers the question: "What do you want to point and where?" Attitude Commanding Attitude offset shall be commanded by specifying a 'rotation' vector in base attitude coordinates or in the S/C basebody coordinates which determines the axis (vector direction) and angle (vector magnitude) of rotation necessary to achieve the offset. The commanded offset rotation axis may be specified in the base attitude or the body attitude coordinates. Attitude Commander allows for both types of offsets. Primary and secondary inertial vectors shall be selected by name from Inertial Vector Propagator entries. Commanded changes to the selection of basebody and/or inertial vectors (not the vector values) shall not be effective until 2-46

91 the first subsequent offset rotation command. That offset command shall be with respect to the most recently selected basebody and inertial vectors. The basebody commander shall accept absolute and relative turn commands. For absolute commands, the basebody commander shall generate the shortest vector turn between the current attitude and a newly commanded offset with respect to the base attitude such that conditions 1, 2, and 3 below are met during the transition. For relative commands, such as spin or turns that are larger than half a revolution, the basebody commander shall accept a turn (or spin) vector, consisting of a turn axis and a turn angle. It will then generate a turn profile between the current attitude and a newly computed offset (with respect to the base attitude) such that the following conditions during the turn are met: (1) The attitude offset with respect to the base attitude (not the attitude with respect to inertial space) rotates predictably about an axis relative to the base attitude; (2) The commanded attitude offset profile is composed of an acceleration phase, an optional constant rate coast phase (if coast rate is reached), and a deceleration phase; and (3) The offset rotation rate with respect to the base attitude reaches zero when the newly commanded offset is achieved. The peak acceleration/deceleration and coast rate of such a turn profile shall be commandable parameters and shall take effect only at the initiation of the next turn profile. Updates to basebody, inertial, and offset vectors, changes in the selections of basebody and inertial vectors, and changes in turn rate profile parameters shall be independently commandable. Other than the inertial and basebody vectors, all other updates shall take effect only at the initiation of the next turn profile Inertial Vector Propagation The Inertial Vector Propagator (IVP) propagates relative inertial positions and velocities between two objects (which may be spacecraft or inertial), e.g. Sun and Earth, Earth and Moon, Sun and Saturn, Saturn and Titan, Titan and spacecraft etc. The propagated vectors are maintained in the Inertial Vector Table (IVT). This table can simultaneously maintain several inertial vectors, a subset of which is generally required to support science instrument pointing, antenna pointing, star tracker pointing, thrust vector pointing, constraint enforcement etc. Although there is no algorithmic restriction, the users (other AACS software objects) generally ask IVP for spacecraft-relative position and velocity vectors. The user may ask IVP for vectors between any two distinct objects propagated by IVP. The Inertial Vector Propagator will add or subtract the required relative vectors (components) to calculate the position and velocity vectors between the user-specified end points. The component vectors are propagated separately and one component may figure in several user requests. The component vectors form a tree, termed the inertial vector "tree". Three types of vector propagation are possible in IVP -- Fixed (time-invariant), Conic (timevarying) and Polynomial (time-varying). The determination of which type is suited best for a particular vector is based on fits carried out on the ground. The Inertial Vector Propagator must be provided with either fixed vectors or sets of propagation constants, each set describing the time-dependent motion of a single component vector. Component vectors need not all be based at the spacecraft. For instance, one set of propagation constants might specify the motion of Saturn with respect to the Sun while other defines the motion of Titan around Saturn. The Body Vector Table (BVT) resident in IVP stores various spacecraft boresights in the AACS body-fixed reference coordinate frame. Entries in the Body Vector Table are not propagated with respect to spacecraft time but are fixed according to user-specified command parameters. 2-47

92 The Body Vector Table allows the user to explicitly accommodate in-flight identification of end-to-end structural and/or electrical misalignments. The vectors are stored as unit vectors Turning the Spacecraft Attitude control of the spacecraft is maintained through the use of the RCS thrusters and the reaction wheel assmblies (RWAs), while attitude determination is controlled through the star trackers, inertial reference units and sun sensors. Most of the attitude control resources are used merely to maintain a constant attitude, limit cycling between the bounds of the pointing requirements. External influences also require attitude control, and the two largest contributors are RTG radiation and solar radiation torques. Turns during cruise are typically done using the RCS system to save the reaction wheel lifetime for the tour period and to allow faster turns to minimize thermal exposure when turning off the Sun line. In situations where the fastest possible turns are required (e.g. for thermal constraints), sprint turns are available at higher rates with degraded pointing accuracy. Turns on thrusters generally take minutes, while turns on wheels can take up to an hour. Finer pointing control is possible with wheels, however, so the need for fast turn times and fine control must be balanced on a case by case basis. Care must be taken to ensure that orientations during turns do not violate thermal constraints or place the Sun, planets or satellites in the boresights of the star trackers and, in some cases, instrument fields of view. Spacecraft resources which are used for turns, mosaics, and target body motion are divided into two groups: torque, which determines the angular acceleration of the spacecraft; and momentum, which determines the maximum rate achievable by the spacecraft. Either resource can limit spacecraft capabilities. For the reaction wheels, the power allocated and some relative balance determines the maximum torque and momentum; for thrusters, the torque is a fixed quantity determined by the thrust provided by the RCS. Momentum (maximum rate) available on the thrusters is tied to the star tracker limits, and to a lesser extent, the propellant required to stabilize the spacecraft during its rotation. Reaction wheels require unloading due to external torques applied to the spacecraft by solar pressure, RTG pressure, etc. During unloads, the thrusters control the spacecraft attitude while the wheels are spun up or down to the desired rate. The reaction wheels must be unloaded (or re-biased) every 15 days, during a tracking pass so the activity can be monitored in real time and the resulting delta-vee measured via navigation tracking. In addition, a re-bias should be placed on the last pass of each sequence to set the wheel speeds properly for the next sequence. The time required to unload the reaction wheels is approximately 15 minutes. For the reaction wheels, mosaics typically use very small turns between frames that never reach the maximum spin rate of either the spacecraft or reaction wheels. Therefore, most of the power can be allocated to torque (i.e., acceleration) to minimize the time required for each mosaic. On the other hand, target turns (e.g. Saturn to Earth) usually spend a lot of time coasting at the maximum rate (determined by momentum). Reaction wheel capabilities are further complicated by variances between wheels, the fact that they are canted with respect to the body axes of the spacecraft, and they operate at various speeds depending on the orientation, biasing at the last reaction wheel unload, and external torques placed on the spacecraft. Each wheel has slight differences in its operating conditions; turns about different axes burden the wheels in different proportions; and the moment-tomoment spin rates of the reaction wheels which indicate how much authority each has available varies with time and the past conditions. For these reasons, articulation capabilities for planning must be selected carefully with an appropriate across-the board margin policy so that the science observations are not too limited, but the risk of not completing a turn is minimal. 2-48

93 Typically, turns about the Z axis provide the best performance. This is due mainly to the fact that the spacecraft moment of inertia is lowest about Z. For reaction wheels, Z axis turns are shared equally between all three wheels which also provides some advantage Target Motion Compensation Target motion compensation is required for some of the highest value science near close flybys when satellites and features must be tracked as they move across the sky quickly. Without TMC, images would be smeared and data corrupted unacceptably. Naturally, the closest encounters can provide the highest potential resolution for images and the strongest measurements of fields, particles and waves, but these flybys also have the highest target motion. During a flyby, each of the two available resources (torque and momentum) must be divided between TMC and any science articulation. As the satellite rate or acceleration increases, more momentum and torque must be devoted to TMC, and less is available for other science turns. If the maximum rate or acceleration limits are reached, no resources are left for science turns. If rate or acceleration limits are exceeded, the target body may move too fast for the science instruments to take advantage of the close encounter. When the spacecraft is engaged in target motion compensation, well-planned science turns can be oriented so they subtract rather than add to the target body rates. In other words, if the target motion should be used to turn from one position to another, rather than requiring the wheels to fight against the target motion. For example, a row of images starting on the leading edge (as seen from the spacecraft) and finishing at the trailing edge will allow the spacecraft to slew from frame to frame by simply compensating less for the target body motion Titan atmospheric model Titan's atmosphere is primarily comprised of a handful of constituents, each of which can be modeled in a formula which approximates the atmospheric density as a function of height from the surface. This formula contains several terms, one for each main constituent, and is based on the PSG endorsed atmospheric model developed by Yelle in A relatively simple formula is possible because Titan's atmosphere is close to isothermic in the Yelle model at the altitudes of interest for this problem (i.e., km). At these altitudes of interest, Titan's atmosphere is comprised mainly of nitrogen, methane and argon. Therefore, there are three terms in the equation, as follows: 11400(z 76) 8030(z+429) 15000(z 44) ρ(z) = 6.35x10 6 e T(z+2575) x10 7 e T(z+2575) x10 5 e T(z+2575) where ρ(z) is the atmospheric density in g/cm3, z is the altitude in km, and T is the stratospheric temperature in Kelvin. Note that this formula is only valid for altitudes between 800km and 3000km. The formula is accurate to within 1% of the altitude in this region. The first term is for nitrogen, the second for methane, and the third for argon. The temperature variation arises only with different confidence levels; again, Titan's atmosphere is isothermic at these altitudes, but what temperature it is fixed at is uncertain. To determine the temperature, the formula T = γ is used, where γ is the gaussian variable; i.e., γ = ± 1 equals a 1-sigma uncertainty (T = 165K or 185K). Gamma is greater than zero for denser atmospheres, and less than zero for sparse atmospheres Minimum Flyby Altitudes Many of the low (< 4000 km) Titan flybys will be allocated to RADAR, when the thrusters will control the spacecraft attitude; most of the remainder will require reaction wheels, particularly 2-49

94 for remote sensing. Both target motion compensation (TMC) and maintaining attitude under atmospheric torque must be possible for the flyby to be useful to the science investigations. Since target motion compensation is required for smear-free imaging of Titan, the reaction wheel or thruster capabilities must be split between atmospheric compensation and TMC. The minimum flyby altitude can therefore be constrained by either of two formulae: that for torque, which has contributions from both TMC and the atmosphere; and that for momentum, which affects the spin rates of the wheels, and has a transient contribution from TMC and a lasting one from the atmosphere. RADAR passes currently use the reaction control thrusters which, compared with the reaction wheels, exerts a strong control over the spacecraft attitude and can rotate it rapidly. However, at the lowest planned altitudes (950 km) Titan's atmosphere becomes a significant source of spacecraft torque. Minimum altitude limits must be set based on the atmospheric model and thruster torque capability. Violating these altitudes will place the spacecraft in an environment where it cannot control its attitude to the desired target(s) for RADAR science. Significant deviations lower than the altitude limits will jeopardize the safety of the spacecraft. Titan's atmosphere, like any, is exponential in nature and has a scale height of about 70 km at the altitudes of interest (this is the altitude required to see a change in density of a factor of e, or 2.7x). Therefore, limit violations as low as tens of kilometers can require significantly higher control torques. One option, besides changing the ORS balance between torque and momentum, which might increase the available momentum is "biasing" the wheels. The momentum available is a vector and not a scalar value. In other words, any momentum limit is defined from 0 Nms in either direction. Since the momentum that the wheels will compensate for is predictable in direction it may be possible to "bias," or pre-spin the wheels in the opposite direction to compensate. This strategy could potentially double the available momentum. The project has adopted a strategy for selecting a minimum altitude for Titan flybys and considering redesign of flyby aimpoints. This strategy is needed to assure efficient use of propellant and to address the potential need to raise or lower the closest approach altitude at several flybys for spacecraft safety and/or INMS science. The design minimum Titan flyby altitude on thrusters is 950 km. This altitude is selected such that the chance of the atmosphere being too dense for the thrusters to maintain attitude control is 5%. If the atmospheric model is more dense than expected, and is refuted by in-situ measurement of the Titan atmosphere during early, higher flybys, then this altitude will have to be increased. For the first 950 km altitude flyby of Titan, two trajectories and sequence plans are developed in parallel, one at 950 km (the baseline) and one at a higher altitude of 1065 km guaranteed to be safe under any possible atmospheric conditions. Both trajectories and sequence plans are canned long before the encounter; after the atmospheric density is measured on the first Titan flyby, a decision is made on which plan is used. If the atmosphere is found to be less dense than expected, future encounters may be lowered to meet INMS science objectives Hydrazine usage The hydrazine tank will be fully loaded at launch to maximize the propellant available at the end of the tour and for any extended mission. 1% of the hydrazine is considered unusable because it may be left over in the tank/lines and loading uncertainty. The Cassini Consumables document, PD , details the expected hydrazine usage during tour. Advance planning and tracking of hydrazine usage should allow for a healthy margin to be maintained. The margin will be available for unexpected occurances during tour should they arise. Any unused hydrazine remaining after tour will be available for use in an extended mission. As propellant is used, the helium pressurant expands to fill the space used by the expended propellant, thereby decreasing the pressure in the tank. When the tank pressure reaches some 2-50

95 minimum level, a second tank containing additional helium pressurant is connected to the hydrazine tank by firing a pyro valve. This effectively raises the pressure of the hydrazine tank. This one-time recharge will likely be used after the probe mission is complete to raise the thrust level for the tour portion of the mission. At launch, the initial pressure of the hydrazine tank is determined by the maximum allowable pressure and temperature of the tank and by the propellant load. The planned propellant load for the Cassini hydrazine tank is 132 kg, which is the maximum allowable load for the tank design. This value represents the maximum pressure at which the thruster is qualified to operate. The maximum flight allowable temperature of the hydrazine tank is 45 C. With the current constraints, the maximum allowable initial pressure of the tank has been calculated to be 370 psia, at an initial tank pressure of 21 C. The pressure after recharge can be calculated in a similar fashion as above. In this case, the propellant load can vary, depending on when in the mission the tank is re-pressurized. The blowdown curve in Figure 2.31 assumes that the recharge occurs when 100 kg of propellant remains in the tank. Given a 100 kg load, and the previous pressure and temperature constraints, the maximum recharge pressure is calculated to be 380 psia. The hydrazine tank pressure needs to be above 250 psia to maintain turn times in the thermally constrained environment inside one AU. The minimum pressure needed during low (950 km altitude) Titan flybys is also 250 psia. Figure 2.31 shows the hydrazine blowdown curve with the recharge after SOI, when approximately 100 kg of hydrazine remains. The range of fuel remaining for SOI and EOM are estimates based on expected values and 50% greater use (AACS) or allocation (Nav). The recharge point may be moved in time depending on whether hydrazine usage is more or less than expected and when higher turn performance is desired. However, there is a pressure which must be reached before the tank can safely be recharged. In the example shown in Figure 2.31, that pressure is 237 psia, based on a recharge with 100 kg of hydrazine in the tank. The maximum allowable pressure prior to recharge is a function of the recharge tank helium load and is fixed at PMS loading, months before launch. The tour will have a series of low Titan flybys. The majority of these low flybys will most likely occur late in the tour. As a result, the hydrazine tank pressure may be allowed to dip below 250 psia early in the tour if there are no Titan low flybys scheduled. However, if the tour has low Titan flybys scheduled early, the tank recharge may need to occur early after the probe mission. Figure 2.31 Hydrazine Tank Pressure (psi) vs. Remaining Fuel 2-51

96 2.7.9 Complications with Reaction Wheel Control A problem with the RWAs occurred on 16 December Increased friction on one of the wheels, operating near zero rpm, caused the spacecraft to autonomously switch to the RCS for attitude control. With the switch to RCS, hydrazine usage increased. Two of the four joint CAPS-HST observations, a Jupiter North-South map, the Himalia "flyby", and a UVIS torus observation were all executed on RCS before the sequence was terminated on 19 December MAPS data continued to be recorded at a reduced rate. All other planned science activities were cancelled until 29 December, when they were resumed. RWA operation was resumed for attitude control on 22 December, with constraints imposed to avoid low RPM regions. This was accomplished by biasing the wheels. Continued testing by AACS personnel suggested the anomaly was a transient event so the sequence was restarted on December 29. Since the anomalous behavior in December 2000, tests and studies led to a Program decision to use RCS as the primary attitude control system whenever possible during cruise. RWA usage has been allowed for certain activities that require increased stability or pointing accuracy, e.g., GWE and RSS tests, and for limited cruise science. For Approach Science starting January 2004, RWA control is the baseline. In order to avoid such anomalies in the future, the low rpm dwell time must be minimized, and continued trending of the RWA performance is required. The low-rpm optimization is performed as a regular step in the sequencing process, by biasing the wheels at speeds which should ensure that they are spinning at moderate to high rpm for most of the sequence, and has not significantly impacted science collections to date. In the later stages of cruise, notably in late 2002 early 2003, another reaction wheel problem was identified as a cage instability on wheel 3. Its symptoms include intermittent drag torque transients and a significant increase in the bearing drag torque. The consequences are large unstable oscillations in the cage, leading to premature bearing failure, and severe transient forces that can cause high wear or fracture which may eventually disable the bearing. Based on project, division, and manufacturer recommendations, the project chose to activate the redundant wheel RWA-4 in July of 2003 and articulate it to the RWA3 position, and use it as a primary wheel together with RWA-1 and 2. It is believed that the RWA-3 cage instability will stay with RWA-3 for its remaining life, and continued operation would increase both the frequency of occurrence and the size of the drag torque steps. Since clearly the two consumable specifications of RWA-3 (total revolutions and total low-rpm dwell time) have been compromised, it is prudent to cut RWA3 usage for the remainder of mission. One of the pointing requests that have been made of the project, in particular by the CDA instrument, is to rock back and forth about a specific attitude during some downlink passes. This enables CDA to collect data that can be used to distinguish dust impacts from various directions, which is a key measurement to their science objectives. Unfortunately, this rocking significantly complicates the low RPM management, depending on number of discrete orientations used, particularly when rocking is required about a large angle (as is the case most of the time). This operation also requires constant commanding during downlink, which would prevent the ground from being able to command an unexpected OTM or RWA unload. However, assuming that the number of rocking passes is on the order of total passes during the tour, the spacecraft office (specifically the attitude control team) and the project have agreed to accommodate the CDA request. The CDA team shall develop a pointing design for such downlinks to be reviewed by the project, and if the RWA management is not too cumbersome, rocking downlinks will be implemented as requested. (For CDA observations which require rocking that do not occur during downlinks, there are no unique restrictions on CDA s pointing designs, just as with any prime instrument planning pointing during an observation period.) 2-52

97 2.8 Environmental hazards & control During the mission, the spacecraft is exposed to a variety of potentially hazardous environments. Careful planning is required to not only ensure that spacecraft health and safety is not compromised, but that creative solutions are developed to balance the risk from these hazards against the scientific objectives when they conflict Radiation Radiation design for the Cassini spacecraft was created using the back-up mission trajectory (March 1999 VEEGA- Venus-Earth-Earth Gravity Assist), because the radiation environment for this mission is the most severe of any of the possible interplanetary trajectories. A radiation design margin of 2 for ionization dose, displacement damage and integrated peak flux was therefore used for all engineering subsystems, bus science electronics, imaging science instruments and the Huygens probe. Science instruments were required to operate with a radiation exposure of 100 krad Thermal Control and Sun Exposure There are several general pointing orientations which expose sensitive components of the spacecraft to undesirable thermal input. This radiative heating can potentially degrade performance or violate safety constraints. The primary source of thermal input at Saturn is the Sun; however, heating from Saturn and its rings, particularly when lit, and the satellites during close approaches are of concern as well. To maintain thermal control during cruise, the spacecraft HGA must remain Sun-pointed for virtually all of its travels in the inner solar system. Off-Sun orientations are possible for short periods of time, as listed in table 5.4, and these durations can be scaled with the square of the Sun range. For example, at 0.61 AU the spacecraft could withstand a transient off-sun duration of 0.5 hours/day. At 0.8 AU, however, the spacecraft could turn 180 off-sun for a scaled duration of about 0.9 hours once/day. For all these off-sun events, the roll angle is restricted so that the sun line lies in the -X (Probe) side of the X-Z plane. For more information about allowable off-sun durations, consult CAS Continuous Continuous off-sun off-sun: Table 2.10 Thermal Capabilities Transient off-sun off-sun exposure at at range Sun Range Off-sun angle Range Off-sun angle Duration AU** AU hours* 1/day AU Earth point OK 1.0 AU hours* 1/day >5.0 AU (unrestricted) 1.0 AU < hours* 1/day *Durations include turn times. **Earth-point OK for 25-day Instrument Checkout. During the later portions of cruise and tour, however, there are performance implications of sun exposure which must be considered. There are three major "exclusion zones" which thermal energy sources should be kept from: the SRU boresights (+X direction), the optical remote sensing instrument boresights (- Y direction), and the cryogenic instrument radiators hemisphere (also centered along +X). First, the SRU performance can be seriously degraded from thermal input within a 30 cone. A gyro-only mode, in which the spacecraft calculates its attitude without the SRU, may be available for short periods of time. Second, most of the remote sensing instruments report some performance degradation from thermal input within a ~15 cone. Third, the cryogenic instrument radiators have hemispherical fields of view and share their exclusion zone with the SRU boresight zone (actually encompassing it completely). Of course, the more vertical the thermal input, the greater the effect on the instruments. Drivers in this zone include VIMS IR and CIRS. Performance, not safety, is the primary concern. Overheating 2-53

98 renders instrument data first degraded, then useless. Overheating for the VIMS IR instrument can be rapid ( tens of minutes with direct sunlight) and cooling very slow ( many hours). There is no absolute temperature threshold; "overheating" depends on the experiment in process. This problem is complicated by the fact that the vast majority of Titan flybys approach on the sunlit side and recede on the dark side of Titan. This is due to inbound and outbound flybys having been placed at consistent locations in Titan s orbit. Unfortunately, the ram direction of INMS and other fields, particles & waves instruments is aligned directly opposite the radiators of the cryogenic instruments. Therefore, in order to point the INMS and other fields of view in the ram direction, the cryogenic instrument radiators must face the sun for many encounters. This problem can be avoided with one of two strategies: pointing the INMS in the anti-ram (instead of ram) direction, or turn the INMS to the ram direction only near closest approach, minimizing the amount of time the radiators are exposed to the sun. Unfortunately, the first strategy degrades data collection for some of the FPW instruments, and the second may use valuable reaction wheel or thruster resources that are needed for TMC or atmospheric compensation. Radiator exposure is still a concern even when the cryogenic instruments are not operating. Since the time constant for cooling is so slow, post-flyby science (even up to a day after exposure) can still be affected. This means that instrument teams that aren t concerned with overheating will still have to constrain themselves in pointing design if cryogenic instrument teams are planning subsequent observations Dust During its travels from the inner solar system to the Saturnian environment, Cassini flies through a large region of space which is known to contain debris at a variety of sizes and abundances. Care must be taken to determine the vulnerabilities of the spacecraft to debris impacts, and the likelihood of such impacts causing the loss of mission or a degradation in performance. For a complete description of Cassini s vulnerabilities to dust, and the protective strategies that have been adopted during the tour, refer to the Cassini Dust Protection Plan D Periodic Activities This section describes activities that are repeated often throughout the mission and are not specific to one particular subphase (as described in sections 6 and 7) Engineering Maintenance There are three activities to be completed in the Periodic Engineering Maintenance (PEM) sequence, which is executed approximately once every three months. The three activities are: Maintaining the BAIL EEPROM in AACS to protect the data from unrecoverable radiation damage. This activity lasts no more than 6 hours. Exercising the engine gimbal actuators (both prime and backup) through 25% of full stroke. This activity lasts one hour. Exercising all of the reaction wheels (including the backup) by rotating each at least 1/4 of a turn to spread the lubricant. This activity lasts for less than one hour. Note that this activity imparts a delta-v to the spacecraft and therefore should not be scheduled near a TCM (-3 weeks to +2 weeks). In addition to the standard PEM activities, there are a number of other required engineering activities. SRU calibration must occur once every year. Maneuver related AACS parameter updates and AACS constraint monitor updates are also common. Also AACS cruise mode checkouts, RWA friction tests, NAC-to-SRU alignment, and HGA(X-band)-to-SRU alignment 2-54

99 are expected. With the exception of the RWA friction test, all of these activities are planned to occur only once. The RWA friction test will occur as needed. Finally, SSR characterization is performed through analysis of the SSR single bit and double bit error information obtained from the internal SSR memory scrub function Huygens Probe Checkouts Probe Checkouts are sequences which exercise the Probe systems to maintain their health during the long cruise period. Each Probe Checkout is up to a 4 hour test of the Probe mission sequence which records up to 303 Mbits of data (including engineering) to the SSR. The purpose of the cruise checkouts is to verify the capabilities of the Probe system to perform its mission at Titan. Therefore, the checkouts have been designed to simulate as closely as possible the sequence of activities to be performed during the Probe descent to Titan. Some experiment switch-on and pyro events excepted, the PCDU (Power Control Distribution Unit) and CDMS (Command & Data Management Subsystem) sequences are performed as during the normal mission, with simulation by telecommands of the changing DDB (Descent Data Broadcast) which will be transmitted to experiments. During checkout, the Probe/PSE link is conducted with a low power RF signal which essentially tests the whole transmitter except for the high power amplifiers. Due to the power allocation limits agreed to between JPL and ESA, not all of the Huygens instrumentation can be operated as it is in the mission descent sequence; therefore, checkout sequences have been developed to allow payload checkout in different groups, and such sequences have been used throughout ground testing activities. ESA will conduct Probe Checkout sequence reviews before each checkout to determine if the specific activities during any one Checkout need to be changed somewhat. Checkouts must take into account the main constraints agreed to by JPL and ESA, namely: Power consumption never to exceed 262 Watts. 1 CDS telecommand per second per data chain. PSA and transmitters in mission mode at switch-on, i.e. the default frequency includes Doppler shift and the Ultra Stable Oscillators (RUSO/TUSO) are selected. Orbiter can be in any RTE mode, but Probe data must be recorded. LGA2 (which is mounted immediately below the probe) cannot be operating during a Probe Checkout (FR80C5). Several additional constraints exist that must be satisfied during each checkout are: For real-time playback, the link must support the Probe Checkout data rate of kbps. If this is not possible, the link margin must support a data rate of at least 40 bps for SSR playback of Probe Checkout data (the lowest mode, 20 bps, is exclusively real-time engineering data with no SSR playback). DSN coverage sufficient to return Probe data must be in the Detailed Mission Request, which documents the antennas requested of the DSN by Cassini, and the MGSO User Loading Profile. Telemetry must not interfere with the navigation ranging required. During those periods where either ranging or telemetry is possible (but not both), a compromise must be reached that allows Probe Checkout data to be returned while still meeting navigation requirements. If Probe telemetry must be played back from the SSR, playback must be completed before being overwritten by later data (2.0 Gbit data capacity at the beginning of the mission Mbit of probe and engineering data leaves 1.7 Gbit of volume to record 2-55

100 engineering at 1650 bps = 11.9 days worth of space). Any nonstandard activities which record additional data on the SSR would shorten this time period. DSN coverage following each Probe Checkout can be used to observe that the probe equipment temperature is falling back to its normal levels (i.e. that everything has been turned off properly). For real-time Probe Checkouts (i.e. those with DSN coverage supporting 24.8 kbps or higher rates), the Probe Checkouts have been placed at the beginning of a pass, leaving at least five hours after the Probe Checkout to study the probe temperature profile. For nonreal-time Probe Checkouts (checkouts 2 and 3), the Checkouts have been placed to end near the beginning of a DSN pass, so that ESA staff may observe the battery temperature over an entire pass ( 8 hours). If SSR playback is possible on this pass, the probe data return is initiated as well. In either case -- real-time or delayed data return -- it is expected that Probe battery temperature readings can be inserted into the Real-Time Engineering (RTE) portion of the telemetry at a granularity acceptable to ESA staff without overly limiting the standard engineering data Periodic Instrument Maintenance PIMs for pre-jupiter cruise were done on IM40 telemetry mode and are described in previous mission plans (Rev. L and earlier). In post-jupiter cruise, the instruments have the opportunity to perform limited maintenance sequences. These limited sequences are contained within the Periodic Instrument Maintenance (PIM) activity for the first few months after Jupiter. The main part of the sequence lasts approximately three and one quarter hours and is completed just prior to DSN coverage. The entire sequence lasts 19 hours and 15 minutes. Data is recorded on the SSR using the RTE 1896 telemetry mode. This mode allows the housekeeping data from all instruments in the PIM to be recorded to the SSR. It does not support the collection of science data. So for the duration of the PIM no science data is recorded. Maintenance activities for RADAR, ISS, VIMS, and CIRS are completed during the first 3 hours and 15 minutes of the PIM. ISS has a decontamination activity that extends for 16 hours after this time. Total time for the PIM is therefore 19 hours and 15 minutes. Starting in fall of 2001, however, each instrument performs instrument maintenance independently Contingency Plans This section contains a summary of the project s position on major, high-level contingencies that have been identified to date. This text documents the bulk of the general discussion amongst the project management, office managers, and key cognizant engineers concering how certain contingencies (deemed most likely to occur) are to be handled When to halt the background sequence (any of the following may apply): 1) Halting the background sequence enables the project to measurably reduce a risk to the health and safety of the spacecraft, including the Huygens probe and science instruments (e.g. an instrument will otherwise be destroyed by Sun exposure). 2) Halting the background sequence enables the project to measurably increase the likelihood of completing the nominal mission (e.g. an OTM required to remain on the tour has been missed; or, the spacecraft is on RCS and the sequence will use excessive hydrazine and render the end-of-mission margins negative). 3) The project has not understood what is happening with the spacecraft, sequence or trajectory and enough time has elapsed to convince mission management that either of the above conditions may be true. 2-56

101 When to declare a spacecraft emergency Document , the system-level procedure titled Declaring a Cassini Spacecraft Emergency, states that a spacecraft emergency should be declared when all resources allocated to Cassini for communicating with the spacecraft have been exhausted, and potential spacecraft health and safety concerns exist. Furthermore, IOM GFS :ms (G. Squibb) states that a spacecraft emergency is defined as any anomaly or on-board condition which requires immediate and unrestricted access to [DSN] resources in order to prevent complete and imminent failure of the mission. The Cassini Program Manager is the only authority recognized by the DSN for declaring a spacecraft emergency. More specifically an emergency may be declared when: 1) The spacecraft is in immediate danger of being lost and added DSN coverage could decrease the likelihood of losing the mission. 2) Project-internal actions, including halting the background sequence, are not sufficient to safeguard the health and safety of the spacecraft (e.g. the project has asked for additional DSN coverage and must declare an emergency to attain it). 3) The project has not understood what is happening with the spacecraft, sequence or trajectory and enough time has elapsed to convince mission management that either of the above conditions may be true. 4) When additional passes are needed, and not otherwise available, for TCMs to keep Cassini on the tour and be able to complete the nominal mission. (i.e. if other Projects will not give up passes voluntarily without a declaration of spacecraft emergency) High-Level Contingency Plans If one of the following contingencies occurs, the SVT lead executes the anomaly response plan. This text is intended as a supporting resource for the SVT lead and anomaly response team. Contingency: Lose part or all of a DSN pass in real-time during execution (pass with no special attributes, e.g. OTM pass). Response: None required. No special effort should be made to manage SSR pointers or otherwise modify playback during that pass. Rationale: There is no time during the pass to determine which data should preferentially be played back, and build and uplink associated commands. Determining preferred data beforehand and precise commands required for any potential loss is intractable and is not a good use of project resources. Ramifications: Science teams, navigation team, and spacecraft office must accept possibility of losing any one pass. Pointers in engineering partitions (P6's) should not be reset whenever possible to allow maximum recording time. OPNAV partition sizes should remain fixed whenever convenient. Contingency: Lose part or all of a primary OTM pass in real-time during execution. Response: If OTM can be uplinked as scheduled (e.g. only latter portion of pass lost), perform maneuver as planned, even if it executes in the blind. Otherwise, plan to execute the maneuver on the backup pass. Rationale: The purpose of backup OTM passes is to address precisely these kinds of contingencies. It is more important that maneuvers execute as planned than execute while the spacecraft is visible. 2-57

102 Ramifications: SVT leads / ACEs must understand precisely how late OTM sequences can be uplinked and still execute cleanly during the pass. Navigation plan and consumables margins should be resilient to loss of any one primary OTM pass. State how much time is needed?? Maybe this is part of the OTM package to the ACES?? If the backup OTM pass is used, some science data normally played back during this pass will be lost. Contingency: Backup OTM pass must be used to execute a maneuver. Response: Navigation team must identify if orbiter can remain on tour with acceptable V impact if maneuver is not executed on backup pass. If not, appropriate staff must be on shift during backup pass and be prepared to request additional DSN support, halt the sequence, build emergency OTM commands as needed, and declare a spacecraft emergency (if necessary). Rationale: Project must be prepared to respond quickly if maneuver cannot be executed during backup window. It is more important to stay on the tour than to preserve any one encounter or equivalent set of science observations. Ramifications: Science sequence may be severely compromised in order to remain on tour and maintain acceptable propellant margins. Contingency: Lose part or all of a sequence upload pass in real-time during execution. Response: Use backup passes to complete uplink of sequence. Rationale: The purpose of backup upload passes is to address precisely these kinds of contingencies. Ramifications: SSUP uplink process must be resilient to loss of any one pass. Typically this is implemented as: uplink IEBs (one 9 hour pass); uplink background sequence (one 9 hour pass); margin (one 9 hour pass); last pass of sequence (one pass). The completion of each SSUP process is linked to the first uplink pass. Contingency: Sequence cannot be uplinked in time. Response: If background sequence is on board, but IEBs are not, continue as planned and uplink IEBs as early as feasible. Otherwise, rebuild background sequence for earliest feasible restart. Typical turnaround for sequence restart with healthy spacecraft is 1 week. Rationale: Sequence cannot be uplinked late. No instruments have identified health and safety issues with IEBs that are not consistent with background sequence. Ramifications: Science and engineering teams should be willing to accept loss of data in first week of a sequence if uplink is late. If health and safety issues are identified with inconsistent IEBs, instruments should bring this to the attention of the project. Instrument response is TBD. Contingency: RWA will spend unforeseen, unacceptable amount of time in low RPM region. Response: Execute unplanned RWA bias during downlink pass. Rationale: RWA biasing strategy must be maintained in light of RWA anomalies to date to maximize likelihood of continued health of wheels. Ramifications: RWA bias can be executed during any downlink pass with little impact to sequence (roll must be stopped; DFPW power margins are sufficient, RSS or DFPW-TCM margins are TBD). AACS team must remain constantly vigilant for wheel speed departures 2-58

103 from modeled profiles via TBD procedure, especially after early low Titan flybys on reaction wheels. Science teams must accept possible interruption to downlink roll. Contingency: Dust model updates identify an unexpected debris crossing. Response: Calculate risk to main engine nozzles and remainder of spacecraft. If crossing constitutes an unacceptable risk to the spacecraft, halt background sequence and uplink commands to assume safe attitude during crossing. If unacceptable risk to nozzles, ensure cover is closed during crossing. Rationale: Maintain health of spacecraft. Ramifications: Science and engineering teams must be prepared to lose observations in order to maintain spacecraft safety (even with significant uncertainties). Dust model updates must be made in a timely manner after arrival via TBD OIA/procedure. Capability to quickly calculate dust hazards required. Contingency: ISS haze anomaly recurs. Response: If the haze anomaly returned, depending on the severity, it is likely that additional decontamination would be desired/required. ISS decontamination heaters for one camera (NAC or WAC) require 27 W. The decontamination could be required for weeks or months. A small amount of degradation would still allow acceptable OPNAVs, although there will be fewer stars or opportunities. The Project will decide whether to use decontamination heaters, and whether to modify instrument ON status in OPMODES. Rationale: ISS images are required for OPNAVs which are necessary for navigating the tour. In addition science images of Titan and icy satellites and Saturn are planned. Ensuring that good images are available is highly desirable. Ramifications: The 27 W is more than the power margin for many OPMODES. Depending on the time in tour, some instruments may have to be turned off to permit ISS decontamination, or there may need to be periods of no decontamination to allow OPMODES to continue. The main ISS OPMODE is ORS RWA and this has 30 W margin at S+3 yrs but only 18W margin at EOM. Contingency: TCM-20 delays cause increased V and jeopardize the Phoebe Flyby. Response: Calculate a priori the V cost vs time. Pick point where Phoebe targeted flyby must be sacrificed in order to preserve reasonable V for tour. Rationale: Do not allow Phoebe delays to significantly impact the overall V available to complete the nominal mission. Ramifications: There are many reasons why the pre-phoebe TCM could be delayed (station problems, ME cover problems, safing, etc.). If the TCM is delayed past some point where significantly increased amounts of fuel are needed to flyby Phoebe, the Phoebe flyby should be dropped. This point should be defined prior to the planned TCM. Contingency: MEA cover does not open for TCM Response: For SOI, Contingency Plan SOI-CP-Act-01 applies. For Tour, if the cover does not open completely, additional attempts will be made. Similar to Contingency Plan SOI-CP-Act- 01, if both ME cover motors singly, or in parallel, do not open the cover completely, the cover may be ejected. Partial cover opening which allows MEA-A to fire may be acceptable if MEA- 2-59

104 A is prime. In the case of motor failures or circuit failures, the cover may be ejected. This would be done by firing pyros to release the cover mechanism. Rationale: During Tour, many TCMs are required using the ME. If the ME cover is not open, safe firing of the ME cannot be done. Ejecting the cover will allow either ME to operate. Note: There is no requirement for MEA-B to be capable of firing as long as MEA-A is available. Ramifications: The ME cover is also used as a dust particle shield for the ME. Once the cover is ejected (or otherwise available), the spacecraft must make turns to a safe attitude whenever crossing dust areas. Contingency: The spacecraft is on an impacting trajectory. Response: If the Spacecraft is on an impacting trajectory, it must change the trajectory to a non-impacting course in order to continue the mission. This will be done with TCMs either in planned windows, backup windows, or a newly scheduled window. Rationale: The mission will be over if the spacecraft impacts Saturn or a satellite. Once on an impacting trajectory, the only way to avoid an impact is to change the trajectory by us\ing a TCM. Ramifications: There will be V costs as well as lost science if other than planned windows are used. Science will be considered expendable while efforts to get off an impacting trajectory are on-going. Contingency: The orbiter falls off the tour. Response: Work with Navigation to determine how soon we can get back on the baseline tour and the V cost. (Process is TBD) By definition, falling off the tour means we cannot simply continue the tour by modifying existing planned TCMs. There will need to be one or more new TCMs planned to return Cassini to a Titan synchronous trajectory. The subsequent tour may or may not have to be redesigned. A tour redesign will take about 4 weeks, followed by a science redesign activity. Rationale: Once the orbiter falls off the tour, it is imperative that a Titan synchronous orbit be re-achieved in order to salvage as many science goals as possible. Without a Titan synchronous orbit, few if any satellite encounters will occur. Ramifications: If we are off the tour, we will lose science data (except FPW) until the tour is resumed and science observations resume. There will likely be a significant V hit to regain the tour. Likely many weeks of tour observing will be lost. Major impact on any extended tour plans. Contingency: The upcoming trajectory includes a Titan flyby at an altitude exceeding the AACS control authority in the planned attitude. Response: If AACS control authority is exceeded, the spacecraft would go into safing, and the attitude of the spacecraft would be unpredictable. Therefore it would be required that the trajectory be modified so as to not exceed the AACS control authority. This would require replanning the prior apoapsis TCM as well as the pre-and post-titan TCMs, to flyby at a higher altitude and also allow continuation on the planned tour. Rationale: Having the spacecraft safe is to be avoided since it will lose science data, both during the safing incident but also during the recovery period (safing recovery is expected to take at least 1 week). 2-60

105 Ramifications: Preliminary studies by navigation indicate that Cassini can fly a tour with minimum altitudes somewhat higher than planned (~ 100 km higher) with little to moderate V impact. However, science replanning may be significant and some science opportunities (e.g. occultations) may be compromised, perhaps severely. Contingency: Another RWA is degraded or lost. Response: If a second RWA is degraded or lost, RWA #3 will likely be reinstated to determine if it can function, if even for a short period. If and when RWA#3 as well as another RWA are not available the choices are a two RWA mission and a thruster-only mission. Two RWA mission is currently under study but would include modifying observations to require only two axis stability. Rationale: Every attempt will be made to extend the useful observation period through EOM Ramifications: A two RWA mission will greatly restrict the type of pointing observations that are available. A thruster-only mission will cause an increase in propellant usage and that will severely restrict observations that have high fuel usage. Contingency: The main engine cover has been ejected (or is not available) Response: If the ME cover has been ejected (or not working), there is no cover protection for the ME. In order to protect the ME from dust particles during ring plane crossings and other debris areas (i.e. near Icy satellites), the spacecraft will need to move to a safe attitude during many more dust crossings than planned. Rationale: The ME operation is susceptible to dust particle impacts and therefore must be protected to ensure ME operation through EOM. Turning the spacecraft to put the ME in the anti-ram direction is the best protection available once the cover is no longer available. Ramifications: Science planning has scheduled science observations for times when the ME cover was considered sufficient protection (i.e. no turn to safe attitude was required). Once the ME cover is unavailable, more turns to a safe attitude will be required and some loss of science date will occur. Contingency: Propellant margins are predicted to be zero or negative by end of nominal mission. Response: Once predictions are made of exceeding propellant margins prior to EOM, observation plans should be modified to stretch the propellant to last until EOM. Examination of high fuel usage activities will be made (e.g., turns on thrusters, RADAR scans). The state of RWA will be important. If some turns can be switched to RWA, some savings is available. If RWA is not available, science activities will need to be curtailed. Analysis of science observations made to date will allow priorities to be set for instruments that have been waiting for near-eom geometry. This is not something that can be done in advance because key parameters are what caused the reduction in the current positive margin, the size of the deficit, and the point in the mission where the negative margins occur. The Project Manager and Science Manager will consider the trade between reducing science or running out of propellant early (which also reduces science). Rationale: The mission is funded for 4 years and every attempt should be made to have propellant sufficient to reach EOM. Ramifications: Reducing science observations that are heavy RCS users may have to be made. Raising low Titan flyby altitudes will be considered. 2-61

106 Contingency: Lose one SSR Response: Tour science has been planned assuming two SSRs. If nothing is done once one SSR is lost, science will be lost based on who gets to use the SSR last. Once the SSR is full, later science will overwrite data already recorded but not played back. There are several options: 1. Use data policing tables to allow all instruments some percentage of their data (average use is 50%) 2. Use data policing tables to prioritize science, allowing higher priority observations a higher percentage than lower priority observations (note: it is very difficult to prioritize science observations). 3. Re-plan all science after the SSR loss to reduce data volume by 50%. This is very workforce intensive. Rationale: Doing nothing is probably not acceptable because data played back is somewhat random as to who will get their data played back. More likely some reasonable re-planning will be done whether using data policing tables or re-planning the science observations. Ramifications: 50% of the planned science data will be lost following the loss of one SSR. A major effort to decide how to reduce data volume by a factor of 2 will be workforce intensive. 2-62

107 MISSED TCM RISK ASSESSMENT Miss TCM TCM error Ephereris error Human error Station down Miss Trajectory Target S/C Recovery (Safing Contingency Plan) Yes Is S/C in Safe Mode? No No On impact trajectory? No Upcoming RPC with dust concerns? Yes Yes take safety actions!v Trades Execute TCM to get off impact trajectory Schedule TCM close ME cover HGA to RAM Deal with trajectory error Nav return to Titan process Return to tour END!V Trades Yes Make-up TCM and stay on tour? No Fall off Tour Frautnick /Strange RECOVERY FROM FALLING OFF TOUR

108 Whan time permits, studty impact of new tour on extended mission plans/design Yes More tour to design? END Plan and implement new leg(s) of tour Fallen Off Tour Nav Process to get back on Titan syncronous trajectory. (Up to 4 week process. Process TBD) detailed trajectory design No Nav return to Titan process END No Can a TCM return us to Titan? Yes Yes SCO evaluation Iterate? time constraint (depends on time untill next Titan Flyby) Science evaluation Nav tour re-design process Plan and implement trajectory to return to Titan Start tour re-design process Resume tour with already planned sequences. (Loss of sequences between event and resumption.) Yes Possible to pick up same tour at later date? No Nav define design for earliest, then latest, part of new tour Science Planning Process to update transition observations. (Parallel Process TBD.) Science Planning Process to update transition observations. Process TBD. END Define future Titan F/B for rest of mission Search for Icy Flybys available with new tour. Search for occultation opportunities with new tour Frautnick /Strange

109 3.0 OPERATIONAL MODES, GUIDELINES AND CONSTRAINTS, AND CONTROLLED SCENARIO TIMELINES THIS SECTION IS UNDER PROGRAM CHANGE CONTROL. This section defines certain elements of the mission and system design for Cassini that are placed under project change control, because they are considered fundamental to the operational strategy for the mission and for constraining operational complexity. These elements include definitions of the operational modes, modules and templates, unique and fixed sequences, transitions, operational guidelines and constraints, and scenario timelines for certain key periods of the mission. 3.1 Operational Mode Definition An operational mode is a resource (power) envelope applied to the spacecraft subsystems and science instruments. The intent of defining operational modes is to maximize the collection of science within a mode (by balancing science and spacecraft power requirements), minimize operational complexity in sequence generation, and allow some flexibility for science instrument states to vary (within the limits of their resource envelopes). The operational mode also uniquely defines the beginning and ending spacecraft state(s) used to transition in and out of the mode. A fixed transition sequence will be defined for each allowed transition between operational modes. The current set of operational modes for the Cassini mission is listed in Table 1.1. Power analysis is one of the mission design primary considerations in verifying the functionality of the operational modes, and this work can be found in the current version of the Cassini Power Report ( ). Some of the modes listed will only have sufficient power for a portion of the mission (e.g., to SOI+2 years). These modes will cease to be available if and when the power margin drops below the required operating margin. Calibration activities for all instruments, except MAG, are included within their normal operating modes. The MAG calibrations require additional power and separate fixed and/or unique sequences. 3.2 Sequence Constructs Definition A module is a reusable sequence of commands whose relative timing and total duration may be variable. A module cannot extend across operational mode boundaries but may be used in more than one operational mode, provided its activities do not violate that operational mode. A module should define a pointing pattern but can be target and telemetry mode independent (provided its activities do not violate the active telemetry mode). A template is a science planning concept (not a sequence construct like a module) which allows convenient reuse of a sequential series of modules, fixed sequences, gaps, or other templates. Templates are used as a conceptual tool to assemble sets of activities that will typically be used in concert and may cross operational mode boundaries. A unique sequence is a sequence that has a specific purpose, is used once, and does not use modules. (If it did, it would not be a unique sequence, it would be a regular sequence.) Unique sequences can and should take advantage of operational modes in their design if possible, but violation of operational mode constraints is permitted. A fixed sequence is a fixed-duration sequence that is designed and validated once for multiple uses, and does not use operational modes, and admits a fixed list of parameters. Both unique and fixed sequence have no defined global constraints and can include any combination of states. Unique or fixed sequences are checked for constraint violations and must contain required state changes needed to transition into and out of specific predefined operational modes. Should the operational modes preceding and/or following the unique or fixed sequence be different, appropriate transition sequences should be added before or after 3-1

110 the sequence to ensure that no sequence redesign is required. Each unique or fixed sequence is checked for constraint violations and must contain required state changes needed to transition into and out of a specific predefined operational mode. Table 3.1 Cassini Operational Modes Operational Mode Mode Type Usage ORS RWAF Science Optical Remote sensing (ORS) pointing and FPW data acquisition with reaction wheel assembly at full power (RWAF) (includes SCAS power). ORS RCS Science ORS pointing and FPW data acquisition during rare occasions using reaction control subsystem (RCS) when thruster control and speed are required (includes SCAS) Downlink/Fields, Particles, and Waves (DFPW)-normal Science FPW data return with or without S/C rotation during downlink. Also ORS pointing and FPW data acquisition not including SCAS power. DFPW-TCM Science FPW data return with or without S/C rotation when a TCM (ME or RCS) is to be done. DFPW-PEM Science FPW data return without S/C rotation during downlink when a engineering activity such as a PEM or RWA friction test is to be done. RADAR RCS Science RADAR and FPW data acquisition using thrusters RADAR RWAF Science RADAR and FPW data acquisitions with RWAs RADAR warmup/radiometry Science ORS pointing, FPW data acquisition, and RADAR warmup or FPW data acquisition and RADAR radiometry RSS PIM RWAF Science ORS pointing and FPW data acquisition with Ka-TWTA on in standby mode for Periodic Instrument Maintenance (PIM). RSS Ka-band RWAF Science Radio science mass or gravity determination or Radio Science engineering activities. Includes ORS and FPW science. X- and Ka-band uplink and downlink. RSS 3a RWAF Science Radio science Titan atmospheric and Saturn atmospheric and ring occultation measurements, includes ORS and FPW science. S-, X-, and Ka-band downlink. (Valid mode for at least first half of Tour.) RSS2 RWAF Science Radio science Titan atmospheric and Saturn atmospheric and ring occultation measurements, includes FPW science. S- and X- band downlink. RSS3 RCS Science Radio Science Titan atmospheric and Saturn atmospheric and ring occultation measurements, includes ORS and FPW science (thruster control). S-, X-, and Ka-band downlink. VIMS low decontamination (decon) heater ORS VIMS low decon DFPW VIMS high decon ORS VIMS high decon DFPW Fixed Sequences Science Science Science Science ORS pointing and FPW data acquisition while operating VIMS low decon heater with VIMS in sleep. FPW data return with or without S/C rotation during downlink while operating VIMS low decon heater with VIMS in sleep. ORS pointing and FPW data acquisition while operating VIMS high decon heater with VIMS in sleep. FPW data return without S/C rotation during downlink while operating VIMS high decon heater with VIMS in sleep. 3-2

111 RWA Unload Engineering RWA unload capability during DFPW-normal opmode. TCM (RCS) Engineering Thruster TCM burn TCM (Main Engine) Main Engine Cover actuation Engineering Engineering Ignition transient and steady state main engine TCM burn. Main engine cover actuation capability during DFPW-normal opmode. EGA Exercise Engineering Engine Gimbal Actuation Exercise capability during DFPW- PEM opmode. EGA exercise draws the peak power during the Periodic Engineering Maintenance (PEM). RWA Friction Test Engineering RWA Friction Test capability during DFPW-PEM opmode. A transition sequence is a fixed sequence that is used to shift between operational modes. A transition sequence is needed when the end state of a operational mode is not the same as the beginning state of the next mode. Operational modes instrument composition is shown in Table 1.2. Transition sequences are shown in Table Requirements on the Design of Operational Modes a) Each operational mode shallspecify a maximum power allocation for each instrument and each engineering function specified in the Operational Mode Tables. [Note: Telemetry modes included in Table 1.3 and 1.4 are merely suggestive, for guidance of the user]. The power and thermal envelopes shall be defined so that operations within those envelopes can be conducted safely without requiring power or thermal analysis by the ground. The maximum power allocations for each science instrument and spacecraft subsystem are shown in Table 1.2. The maximum value is the peak power. b) Operational modes shall be designed so as to allow sequencing of system-level activities in the mode through the use of standard sequence components. c) Each operational mode shall have a defined spacecraft state for mode start and mode end. Each of the allowed transitions between end and start states of the different operational modes shall be via transition sequences using standard sequence components. d) Operational modes shall be designed so as to allow sequencing of system-level activities necessary to transition between modes. 3.4 Requirements on the Design of Modules The following rules for module construction and usage shall be followed: a) All modules shall be reusable without validation. As a consequence, the use of module parameters within a module expansion shall be limited to changing either command parameters or the number (greater than or equal to one) of repetitions of actions within the module. b) The module shall include target-relative pointing (but need not be target-specific), telemetry mode, and trigger commands which need to be time synchronized over the execution period of the module. c) Modules shall allow for instrument trigger commands (that are permitted within the operational mode) that are independent of spacecraft pointing, independent of the allowed telemetry mode choices, and that do not need to be synchronized with any other module actions to be executed in parallel with the module. 3-3

112 d) Modules shall not cross operational mode boundaries. Modules need not assume a specific operational mode, provided their execution will not violate the conditions of the operational mode(s) in which they may be placed. e) Each command contained in a module shall execute at a time relative to a base time. These execution times may be parameters of the module. f) Module design shall not assume any telemetry mode is in effect at the beginning of the module. g) Only one module shall execute at a time and a module shall not initiate another module. h) The Prime Instrument shall define the pointing profile, telemetry mode changes, and module base time for each execution of a module. Rationale: Defines what is meant by a module and what the constraints are. For a module to save costs, it must be trusted without validation. To make such a validation realizable, the use of parameters is limited to either changing the parameters of commands in the module expansion (e.g. timing), or changing the loop counts of repeated actions (e.g. scans or images or dimensions of a mosaic). This allows validation at the "edge of the envelope" of the possible module expansions. What is not permitted is a module with parameters that turn off some operations and turn on others, since then the amount of validation needed can grow exponentially to adequately cover all possible expansions. When that is needed, separate modules need to be written for different operations. Modules must allow instrument operations that do not depend on the spacecraft orientation, or on which allowed data mode in that operational mode is active, to be placed anywhere in the time the module occupies. Modules are distinct from transition sequences used to change operational modes, and distinct from each other. While the module cannot cross operational mode boundaries, it must set one of the allowed data modes for that operational mode at the start, to avoid having to interface between modules. 3-4

113 Table 1.2 Operational Mode Composition ORS (RWA) ORS (RCS) Downlink FP-normal Downlink FP- TCM Downlink FP- PEM RADAR wu/rad Margin Power Violations ORS CIRS on 46.0 on 46.0 on 46.0 on_ss 34.0 on 46.0 on_ss 34.0 ISS on 45.6 on 45.6 on 45.6 sleep 38.7 sleep 38.7 on 45.6 UVIS on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 VIMS on 27.3 on 27.3 on 27.3 sleep 12.9 sleep 12.9 on 27.3 MAPS CAPS on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 CDA on 25.0 on 25.0 on 25.0 on 25.0 on 25.0 on 25.0 INMS on 26.6 on 26.6 on 26.6 on 26.6 on 26.6 on 26.6 MAG on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 MIMI on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 RPWS on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 SCAS on 24.0 on 24.0 off 0.0 off 0.0 off 0.0 off 0.0 R F RADAR off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 wurad 53.0 RSS/KAT kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 RSS/KEX off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/KaTWTA off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/SBT off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 Instruments Total Total Total Total Total Total AACS Base AFC (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 SRU SRU Supp Htr SRU Repl Htr Sun Sensor IRU RWA full 90.4 off 0.0 full 90.4 full 90.4 full 90.4 full 90.4 RCS VDECU on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 MPD on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 Thrusters off off 0.0 off 0.0 off 0.0 off 0.0 Catbed Htrs Main Engine Accelerometer off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA heaters off 0.0 off 0.0 off 0.0 on 34.0 off 0.0 off 0.0 REA valve off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA OX htr (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 EGA off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 AACS Subtotal Subtotal 90.2 Subtotal Subtotal Subtotal Subtotal PMS Press. Xdcrs (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 PCA Line Htr Temp Control RSP R/Htr htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 ATCs RFS X-TWTA sleep 10.7 sleep 10.7 on 50.6 on 50.6 on 50.6 sleep 10.7 DST TCU USO CDS CDS (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 CDS EU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 PMS REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 RSP REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 REU delta SSR (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 PPS Pwr Control Pwr Distrib PPS REU (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 SSPS Losses Cable Losses Rad. & Age Thermal Flux RWA on 6.0 RWA off 0.0 RWA on 6.0 RWA on 6.0 RWA on 6.0 RWA on 6.0 FP Margin Engineering Total Total Total Total Total Total RTG@SOI margin RTG@EOM

114 RADAR (RWA) RADAR (RCS) RSSP (RWAF) RSSK (RWAF) RSS3a (RWAF) RSS2 (RWAF) Margin Power Violations >EOM by 3 >EOM by 22.5 ORS CIRS on_ss 34.0 on 46.0 on 46.0 on_ss 34.0 on_ss 34.0 on_ss 34.0 ISS sleep 38.7 on 45.6 on 45.6 on 45.6 on 45.6 sleep 38.7 UVIS on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 VIMS sleep 12.9 on 27.3 on 27.3 on 27.3 on 27.3 sleep 12.9 MAPS CAPS on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 CDA on 25.0 on 25.0 on 25.0 on 25.0 noart 11.7 on 25.0 INMS on 26.6 on 26.6 on 26.6 on 26.6 on 26.6 on 26.6 MAG on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 MIMI on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 RPWS on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 SCAS off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 R F RADAR on 85.3 on 85.3 off 0.0 off 0.0 off 0.0 off 0.0 RSS/KAT kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 off 0.0 kat_on 8.9 RSS/KEX off 0.0 off 0.0 kex_on 3.6 kex_on 3.6 kex_on 3.6 off 0.0 RSS/KaTWTA off 0.0 off 0.0 standby 8.0 katwta_op 35.1 katwta_opr 35.1 off 0.0 RSS/SBT off 0.0 off 0.0 off 0.0 sbt_on 41.7 sbt_on 41.7 Instruments Total Total Total Total Total Total AACS Base AFC (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 SRU SRU Supp Htr SRU Repl Htr Sun Sensor IRU RWA full 90.4 off 0.0 full 90.4 full 90.4 full 90.4 full 90.4 RCS VDECU on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 MPD on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 Thrusters off off 0.0 off 0.0 off 0.0 off 0.0 Catbed Htrs Main Engine Accelerometer off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA heaters off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA valve off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA OX htr (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 EGA off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 AACS Subtotal Subtotal 90.2 Subtotal Subtotal Subtotal Subtotal PMS Press. Xdcrs (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 PCA Line Htr Temp Control RSP R/Htr htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 ATCs RFS X-TWTA sleep 10.7 sleep 10.7 on 50.6 on 50.6 on 50.6 on 50.6 DST TCU USO CDS CDS (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 CDS EU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 PMS REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 RSP REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 REU delta SSR (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 PPS Pwr Control Pwr Distrib PPS REU (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 SSPS Losses Cable Losses Rad. & Age Thermal Flux RWA on 6.0 RWA off 0.0 RWA on 6.0 RWA on 6.0 RWA on 6.0 RWA on 6.0 FP Margin Engineering Total Total Total Total Total Total RTG@SOI margin RTG@EOM margin

115 RSS3 (RCS) RWA Unload (DFPW) TCM RCS TCM ME ME Cover EGA Exercise (PEM) Margin delta from DFPW delta from DFPW_normal Power Violations ORS CIRS on 46.0 on 46.0 on 46.0 on_ss 34.0 on_ss 34.0 on 46.0 ISS on 45.6 on 45.6 sleep 38.7 sleep 38.7 on 45.6 on 45.6 UVIS on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 VIMS on 27.3 on 27.3 sleep 12.9 sleep 12.9 on 27.3 on 27.3 MAPS CAPS on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 CDA on 25.0 on 25.0 on 25.0 noart 11.7 on 25.0 on 25.0 INMS on 26.6 on 26.6 on 26.6 sleep 16.6 on 26.6 on 26.6 MAG on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 MIMI on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 RPWS on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 SCAS off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 R F RADAR off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/KAT kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 RSS/KEX kex_on 3.6 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/KaTWTA katwta_opr 35.1 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/SBT sbt_on 41.7 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 Instruments Total Total Total Total Total Total AACS Base AFC (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 SRU SRU Supp Htr SRU Repl Htr Sun Sensor IRU RWA off 0.0 full 90.4 full 90.4 off 0.0 full 90.4 limited 60.4 RCS VDECU on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 MPD on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 Thrusters off 0.0 off 0.0 Catbed Htrs Main Engine cover motor 15.0 Accelerometer off 0.0 off 0.0 off 0.0 on 3.1 off 0.0 off 0.0 REA heaters off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA valve off 0.0 off 0.0 off 0.0 trans 90.0 off 0.0 off 0.0 REA OX htr (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 EGA off 0.0 off 0.0 off 0.0 on 49.0 off 0.0 on 49.0 AACS Subtotal 90.2 Subtotal Subtotal Subtotal Subtotal Subtotal PMS Press. Xdcrs (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 PCA Line Htr Temp Control RSP R/Htr htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 ATCs RFS X-TWTA on 50.6 on 50.6 on 50.6 on 50.6 on 50.6 on 50.6 DST TCU USO CDS CDS (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 CDS EU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 PMS REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 RSP REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 REU delta SSR (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 PPS Pwr Control Pwr Distrib PPS REU (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 (2) 5.4 SSPS Losses Cable Losses Rad. & Age Thermal Flux RWA off 0.0 RWA on 6.0 RWA on 6.0 RWA off 0.0 RWA on 6.0 RWA on 6.0 FP Margin Engineering Total Total Total Total Total Total RTG@SOI margin RTG@EOM margin

116 RWA Friction Test VIMS Decon Low-ORS VIMS Decon Low-DFPW VIMS Decon High-ORS VIMS Decon High-DFPW Margin delta from DFPW_PEM Power Violations ORS CIRS on_ss 34.0 on 46.0 on_ss 34.0 on_ss 34.0 on_ss 34.0 ISS sleep 38.7 on 45.6 on 45.6 on 45.6 on 45.6 UVIS on 13.0 on 13.0 on 13.0 on 13.0 on 13.0 VIMS sleep 12.9 sleep/d-low 51.9 sleep/d-low 51.9 sleep/d-high sleep/d-high MAPS CAPS on 21.0 on 21.0 on 21.0 on 21.0 on 21.0 CDA on 25.0 on 25.0 on 25.0 on 25.0 on 25.0 INMS on 26.6 on 26.6 on 26.6 on 26.6 on 26.6 MAG on 13.4 on 13.4 on 13.4 on 13.4 on 13.4 MIMI on 25.9 on 25.9 on 25.9 on 25.9 on 25.9 RPWS on 16.9 on 16.9 on 16.9 on 16.9 on 16.9 SCAS off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 R F RADAR off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/KAT kat_on 8.9 kat_on 8.9 kat_on 8.9 kat_on 8.9 off 0.0 RSS/KEX off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/KaTWTA off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 RSS/SBT off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 Instruments Total Total Total Total Total AACS Base AFC (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 (2) 19.6 SRU SRU Supp Htr SRU Repl Htr Sun Sensor IRU RWA 4 wheels full 90.4 full 90.4 full 90.4 limited 60.4 RCS VDECU on 2.1 on 2.1 on 2.1 on 2.1 on 2.1 MPD on 1.7 on 1.7 on 1.7 on 1.7 on 1.7 Thrusters off 0.0 off 0.0 off 0.0 off 0.0 Catbed Htrs Main Engine Accelerometer off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA heaters off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA valve off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 REA OX htr (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 (2) 4.4 EGA off 0.0 off 0.0 off 0.0 off 0.0 off 0.0 AACS Subtotal Subtotal Subtotal Subtotal Subtotal PMS Press. Xdcrs (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 (18) 5.8 PCA Line Htr Temp Control RSP R/Htr htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 htr off 0.0 ATCs RFS X-TWTA on 50.6 sleep 10.7 on 50.6 sleep 10.7 on 50.6 DST TCU USO CDS CDS (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 (2) 24.0 CDS EU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 PMS REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 RSP REU (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 (2) 6.2 REU delta SSR (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 (2) 19.5 PPS Pwr Control Pwr Distrib PPS REU (2) 5.4 (2) 6.6 (2) 5.4 (2) 5.4 (2) 5.4 SSPS Losses Cable Losses Rad. & Age Thermal Flux RWA on 6.0 RWA on 6.0 RWA on 6.0 RWA on 6.0 RWA on 6.0 FP Margin Engineering Total Total Total Total Total RTG@SOI margin RTG@EOM margin

117 Table 3.3 Cassini Peak Data Rate Guidelines by Operational Mode Preferred Op Mode vs. Telemetry Mode Usage S&ER-1 S&ER-2 S&ER-3 S&ER-4 S&ER-5 S&ER-5a S&ER-6 S&ER-7 S&ER-8 RTE & SPB OP MODE TYPES ORS x x x x x x x DL FPW or RWA Unload x RADAR wu x RADAR rad x x RADAR full x RSS wu x x x x x x x x RSS/RCS x x x x x x x x x RSS/RWA x x TCM x x 3-10

118 Table 3.4 Telemetry Mode Pickup rates S&ER-1 S&ER-2 S&ER-3 S&ER-4 S&ER-5 S&ER-5a S&ER-6 S&ER-7 S&ER-8 RTE & SPB Stellar occultations Titan Saturn Saturn Icy Satellites & OpNav Icy Satellites Icy Satellites FPW & INMS RADAR/ INMS DL FPW ORS CIRS ISS UVIS VIMS MAPS CAPS CDA INMS MAG MIMI RPWS RADAR Notes: RADAR warmup is in S&ER-5A RADAR radiometry is in S&ER-5A or S&ER-8 RADAR full power is in S&ER

119 Table 1.5 Mode to Mode Transitions Table 1.5 Mode to Mode Transitions TO FROM ORS (RWAF) ORS (RCS) DFPWnormal DFPW-TCM DFPW-PEM RADAR Wu/Rad RADAR (RWA) RADAR (RCS) RSSP (RWAF) RSSK (RWAF) RSS3a RWAF RSS2 (RWAF) RSS3 (RCS) 1 ORS (RWAF) RWA_2_RCS 2 ORS (RCS) RCS_2_RWA 3 DFPW-normal X_standby 4 DFPW-TCM 5 DFPW-PEM ME_htr_off X_standby ORS_wake X_standby ORS_wake X_standby RWA_2_RCS ME_htr_off X_standby ORS_wake RWA_2_RCS X_standby ORS_wake RWA_2_RCS 6 RADAR Wu/Rad RADAR_low_off RADAR_low_off RWA_2_RCS 7 RADAR (RWA) 8 RADAR (RCS) RADAR_off ORS_wake RADAR_off RCS_2_RWA RADAR_off ORS_wake RWA_2_RCS RADAR_off SCAS_off X_operate SCAS_off RCS_2_RWA X_operate ME_htr_off ORS_wake ORS_wake RADAR_low_off X_operate RADAR_off ORS_wake X_operate RADAR_off RCS_2_RWA X_operate SCAS_off ORS_sleep X_operate ME_htr_on SCAS_off ORS_sleep RCS_2_RWA X_operate ME_htr_on ORS_sleep ME_htr_on N RADAR_low_off ORS_sleep X_operate ME_htr_on RADAR_off X_operate ME_htr_on RADAR_off ORS_sleep RCS_2_RWA X_operate ME_htr_on SCAS_off ORS_sleep X_operate SCAS_off ORS_sleep RCS_2_RWA X_operate ORS_sleep N RADAR_low_off ORS_sleep X_operate RADAR_off X_operate RADAR_off ORS_sleep RCS_2_RWA X_operate SCAS_off RADAR_low_on SCAS_off RCS_2_RWA RADAR_low_on X_standby RADAR_low_on ME_htr_off X_standby ORS_wake RADAR_low_on X_standby ORS_wake RADAR_low_on RADAR_high_off ORS_wake RADAR_high_off RCS_2_RWA 1>7>8 Rad_wu 2>7>8 Rad_wu 3>7>8 Rad_wu 4>7>8 Rad_wu 5>7>8 Rad_wu ORS_sleep RADAR_high_on ORS_sleep RCS_2_RWA SCAS_off RWA_2_RCS RADAR_on SCAS_off RADAR_on X_standby RWA_2_RCS RADAR_on ME_htr_off X_standby ORS_wake RWA_2_RCS RADAR_on X_standby ORS_wake RWA_2_RCS RADAR_on RWA_2_RCS RADAR_high_o n RWA_2_RCS ORS_wake SCAS_off RCS_off X_operate RSS_P_on SCAS_off RCS_2_RWA RCS_off X_operate RSS_P_on RCS_off RSS_P_on ME_htr_off RCS_off ORS_wake RSS_P_on RCS_off ORS_wake RSS_P_on RADAR_low_off RCS_off X_operate RSS_P_on RADAR_off ORS_wake RCS_off X_operate RSS_P_on RADAR_off RCS_2_RWA RCS_off X_operate RSS_P_on N N RCS_off RSS_P_on RSS_K_on N N N N N SCAS_off KaT_off RCS_off X_operate RSS_sKa_on SCAS_off KaT_off RCS_2_RWA RCS_off X_operate RSS_sKa_on KaT_off RCS_off RSS_sKa_on ME_htr_off KaT_off ORS_wake RCS_off RSS_sKa_on KaT_off RCS_off ORS_wake RSS_sKa_on KaT_off RADAR_low_off RCS_off X_operate RSS_sKa_on KaT_off RADAR_off ORS_wake RCS_off X_operate RSS_sKa_on KaT_off RADAR_off RCS_2_RWA RCS_off X_operate RSS_sKa_on SCAS_off ORS_sleep RCS_off X_operate RSS_S_on SCAS_off ORS_sleep RCS_2_RWA RCS_off X_operate RSS_S_on ORS_sleep RCS_off RSS_S_on ME_htr_off RCS_off RSS_S_on RCS_off RSS_S_on RADAR_low_off ORS_sleep RCS_off X_operate RSS_S_on RADAR_off RCS_off X_operate RSS_S_on RADAR_off ORS_sleep RCS_2_RWA RCS_off X_operate RSS_S_on 9 RSSP (RWAF) N N N N N N N N RSS_K_On N N N RSS_off RSS_off RSS_off via ORS RWA RSS_off ORS_sleep X_standby via RadWu for at 10 RSSK (RWAF) X_standby for at least 32 RSS_off RCS_on ORS_sleep 11>7>8 Rad_wu N N N N RCS_on RCS_on least 32 minutes RCS_on minutes RCS_on ME_htr_on RADAR_low_on 11 RSS3a RWAF 12 RSS2 (RWAF) 13 RSS3 (RCS) RSS_off X_standby RCS_on RSS_off X_standby ORS_wake RCS_on RSS_off X_standby RCS_2_RWA via ORS RWA for at least 32 minutes via ORS RWA for at least 32 minutes RSS_off X_standby RSS_off RCS_on RSS_off ORS_wake RCS_on RSS_off RCS_2_RWA RSS_off ORS_sleep RCS_on ME_htr_on RSS_off RCS_on ME_htr_on RSS_off ORS_sleep RCS_2_RWA ME_htr_on RSS_off ORS_sleep RCS_on RSS_off RCS_on RSS_off ORS_sleep RCS_2_RWA RSS_off X_standby RCS_on RADAR_low_on RSS_off X_standby ORS_wake RCS_on RADAR_low_on RSS_off X_standby RCS_2_RWA RADAR_low_on 12>7>8 Rad_wu 13>7>8 Rad_wu 14>7>8 Rad_wu via RadWu for at least 32 minutes via RadWu for at least 32 minutes RSS_off X_standby RADAR_on 1>2>14 ORS_RCS SCAS_off X_operate RSS_sKa_on 3>2>14 ORS_RCS 4>2>14 ORS_RCS 3>2>10 ORS_RCS 7>2>14 ORS_RCS 8>2>14 ORS_RCS RADAR_off X_operate RSS_sKa_on N N N N N N N N N N N N Grey N = not allowed Green = can be done via warmup trans Limited Power 3-12

120 3.5 Mission Design Guidelines & Constraints The purpose of this subsection and Subsections 1.3 and 1.4 is to establish mission design guidelines and constraints that govern how the various Program systems and subsystems will be used to achieve science return, while providing assurance that the scenarios can be reliably developed with the available Program resources. These guidelines and constraints are intended to establish an envelope within which the mission scenarios are designed, developed, implemented, and executed. This minimizes unnecessary optimization and management turbulence. In general, these items are of a medium to long-range planning nature. Their purpose is to define and balance the interfaces between the Spacecraft Office, the Mission Support and Services Office, and the Science and Uplink Operations Office. The distinction between a guideline and a constraint is as follows. Each constraint is binding, necessitating formal waiver approval if it is to be violated. Guidelines have a solid level of support within the Program and should therefore be honored if they do not lead to appreciable science loss or increase in mission risk and cost. Guidelines & constraints have been organized by topic and labeled with NNNNN - G# for guidelines and NNNNN - C# for constraints. The 3-5 letter abbreviations NNNNN stand for the category of the guideline or constraint: OPS for Operational Modes and Sequence Constructs, SEQ for Sequence Development, POINT for Spacecraft Pointing, TEL for Telecommunications Strategies for Uplink & Downlink, DATA for Management of On-Board Data, PRESAT for Pre-Saturn Science Activities, ESB for Earth Swingby, MEO for main engine operations, and MISC for Miscellaneous. Numbering is done by category and restarted each new subsection. During the post-launch scenario development, the Mission Design Team has three principal areas of responsibility: a) Perform long-term studies to show feasibility of scenarios within consumable constraints and Program operating constraints; b) Develop and update appropriate mission design guidelines and constraints; Coordinate scenario design with the science and uplink teams to ensure consistency with the guidelines and constraints Operational Modes and Sequence Constructs Constraint OPS-C1 Operational Mode Usage Each operational mode shall be defined in Subsection 1.1 and adhere to the design constraints in Subsection and Rationale: See discussion in Subsection Constraint OPS-C5 Transitions from Operational Mode to Unique Sequence The state transitions required from (to) any operational mode into (out of) a unique sequence shall be built into the unique sequence. Rationale: Consolidates the unique sequence design activity into one effort. Constraint OPS-C6 Allowed Instrument Commanding Instrument state changes within an operational mode shall not require any CDS controlled heater commands. Rationale: This and the power allocations in Table 1.2 will ensure that remotely generated state change commands by the instruments do not require special integration into the spacecraft sequence. Constraint OPS-C7 Operational Mode Transitions All spacecraft activities required to change from one mode to another mode shall be defined in a transition sequence. Standard transition sequences shall be used for the mode switches 3-13

121 indicated in Table 1.5 The scenario design shall allow windows long enough and sufficient power margins for all transition activities. Science is permitted during a transition if an instrument is on in both the preceding and following mode. During the transition, however, the instrument has no flexibility for state changes other than those required during the transition. Rationale: Defines transition rules, prevents arbitrary science interruptions Sequence Development Constraint SEQ-C3 Scenario Development Activity Priority Windows shall be inserted during scenario development for the following activities, in the following priority: a) Propulsive Maneuvers and Supporting Activities Rationale: Windows shall be set aside for spacecraft propulsive maneuvers and their corresponding turn times. OPNAV opportunity windows to support maneuver design shall be inserted. (Note that science activities are permitted if they do not conflict with the maneuver or supporting activities.) b) Reaction Wheel Unloads Rationale: Reaction wheel unloads shall be scheduled periodically from SOI-6 months to EOM, when the predicted accumulated angular momentum reaches a SCO defined limit. c) Science Activities Rationale: Windows shall be inserted for science activities and their related engineering support activities, including OPNAV images scheduled to enhance pointing performance, if necessary. d) Other Engineering Activities Rationale: Windows shall be provided for engineering activities including performance tests and calibrations. Constraint SEQ-C5 OP NAV Sequencing Spacecraft Operations (Navigation) personnel shall act as the Prime Instrument Team for the purpose of sequencing optical navigation images. Rationale: Avoids an additional unique interface. Constraint SEQ-C6 Late Update No more than one late update (change to sequence prior to uplink) per sequence during the Saturn tour shall be allowed to incorporate sequence changes due to navigation and spacecraft clock drift updates. Rationale: Late updates allowed to meet accuracy requirements, primarily for targeted satellite flybys during the tour. Limit of one late update minimizes the Sequence Virtual Team workload. Late updates will only be changes to target vectors and module start times, and will be inserted into the sequence process as determined by the SVT. Should there be more than one tour targeted flyby in a sequence, pointing requirements may not be able to be met on all flybys unless multiple late updates to update pointing are approved by the Program. Constraint SEQ-C7 Live Update No more than one sequence "live update" (change to sequence pointing and timing after it has been uplinked) per week shall be allowed. The live update capability shall be supported beginning with the Approach Science subphase, approximately SOI - 6 months. Rationale: "Live updates" are needed to meet accuracy requirements. Limit of one "live update" per week limits the Sequence Virtual Team workload. "Live updates" will only be changes to IVP and movable block start times. 3-14

122 Constraint SEQ-C8 DSN Support for Real-time Commands Real-time commands shall not require additional DSN passes over those regularly scheduled, except to support spacecraft emergencies or critical events. Rationale: DSN passes are a critical resource, and except for emergencies or critical events, it is prudent to limit real-time commanding to regularly scheduled passes. (Real-time commands may be sent during any pass scheduled for other purposes.) Constraint SEQ-C9 On-board Distributed Sequence Timing Changes Once a distributed sequence has been loaded on-board, all timing changes (such as ephemeris changes, clock drifts, or movable blocks) that affect system-level commands and activities shall be implemented by changing CDS command execution times. Rationale: Changes to internal instrument sequence timing could result in unexpected interactions. For example, no instrument commands that independently change the timing of microphonics are allowed. Constraint SEQ-C10 Triggered Instrument Execution Time Definition Instrument execution time in a trigger command shall be a relative time (as opposed to an absolute time) and is defined to be relative to the receipt of the trigger command by the instrument. Rationale: Distributed sequencing does not mean independent sequencing--all instrument activities must be directly tied to the CDS sequence, and can be shifted or canceled by changing only the CDS sequence. Constraint SEQ-C12 Huygens Probe Checkout Sequencing Constraint No other spacecraft activities shall be sequenced during a Probe Checkout. Rationale: MPVT/SPVT /SVT cannot verify that CDS command bandwidth would not be exceeded in the presence of other activities, since Probe telecommand frequency cannot be checked explicitly. Constraint SEQ-C13 OPNAV Image Return (was a guideline, SEQ-G3) Optical navigation images shall be returned at the next available downlink opportunity following exposure. All OPNAV images shall be compressed using lossless compression to reduce the total volume of OPNAV data downlinked. Rationale: Time-critical navigation products require that OPNAVs be returned as soon as possible. Op Nav data volume shall be compressed to increase science data allocation. Constraint SEQ-C15 Superior Conjunction Downlink Data Rate Downlink data rate shall be reduced to 1896 bps (RTE or S&ER) when the SEP angle falls to 2.0 or lower. Rationale: X-band capability begins to be degraded when the SEP angle is low and degrades more as the angle decreases bps is the minimum data rate which can record science data and provides higher reliability during down link than higher rates. The constraint does not forbid the recording of science data during the SEP<2 period. Constraint SEQ-C16 SSR Library Allocation Restriction No team shall write to nor read from any portion of the Library Region of the SSR that is beyond their allocated space. The library region will always be flown as non-equivalent, except during the Probe Relay mission, when the Library Region will be flown equivalent since it contains the vectors for the relay. Rationale: Writing information beyond the assigned allocation will likely result in overwriting another team s commands. Reading from areas outside the assigned space will have unexpected in-flight results. Library Region Allocation 3-15

123 Subsystem Default Partions 0 & 1 Non-default Partions 2 & 3 Starting Record # # ALFs % Total Max # IEB Starting Record # # ALFs % Total Max # IEB CDS NA NA OPNAV Probe/Seq NA NA SVT modules NA CAPS CIRS CDA INMS ISS MAG MIMI RADAR RPWS UVIS VIMS reserve N/A NA Total Constraint SEQ-C17 Validation of Instrument Commands For all orbiter instruments, all instrument commands are to be validated on that instrument s engineering model prior to first time transmittal to and execution on the spacecraft. Rationale: First time use of instrument commands are more likely to cause unforeseen events. Note: Validation of all instrument sequences on engineering models is encouraged as resources permit, but is not required, once all commands in a sequence have been previously validated and subsequently executed in flight. Constraint SEQ-C18 Downlink Pass Block There shall be only one downlink pass block in the background seuence for each primary and backup TCM/OTM pass. For split passes, the downlink pass block shall execute at the beginning of the pass. Rationale: Downlink pass blocks produce numerous 6ASSIGN commands as part of the block expansion. If a downlink pass block executes after the beginning of a pass, there is a possibility these commands might ovelap with the OTM block execution. If 6ASSIGNs execute during OTM execution, this may disrupt the OTM block s telemetry strategy and cause loss of science and engineering data during the OTM. Guideline SEQ-G2 OPNAV Image Scheduling Optical navigation images should be scheduled at a rate of no more than 8 per day during the tour. OPNAVs should only be scheduled when such data (including reasonable margin) significantly improve TCM design, near target pointing, satellite ephemerides, or trajectory reconstruction. Rationale: Defines the maximum needed. 3-16

124 Guideline SEQ-G6 Superior Conjunctions Spacecraft activities should be limited when the SEP angle is 3.Spacecraft pointing changes should not be requested inside 3 (however, rolls about the Z-axis, with Z to Earth, are allowed) Planned activities should not require successful commanding inside 3, or successful playback inside 2. Downlinks should not be requested inside 1, except for cruise Radio Science Conjunction experiments. Rationale: X-band capability begins to be degraded when the SEP angle is low and degrades more as the angle decreases. The minimum angle for communication depends on solar noise conditions. Limiting spacecraft activities during known periods of uncertain communication is prudent. Downlinks inside 1 SEP are unlikely to be successful. Guideline SEQ-G7 Timing Control Ring or Saturn observations which need timing control better than 13 seconds (1 σ) should be scheduled on orbits with no Titan inbound encounter. Rationale: Titan perturbs the orbit and tight timing control may not be available at Saturn. Preliminary analysis indicates timing uncertainties following a Titan encounter range from about 2to 60 seconds (1 sigma), depending on the altitude of the flyby (the larger uncertainties from closer flybys). Guideline SEQ-G8 Quiet Periods Development and Operations activities should allow for vacations and/or reduced workload during weekends and JPL observed holidays. Rationale: Allows for time off to prevent staff overload. During these periods every attempt should be made to manage activities that require special preparation, analysis or monitoring. Guideline SEQ-G10 First Time Event Scheduling First Time cruise events should not be scheduled in the same sequence time period as a key spacecraft event (e.g., probe activities, unique activities with a geometric constraint such as encounters or opposition experiments) in order to allow adequate time to recover from possible safing between the first time event and the key event. Rationale: First time activities are unproven in flight and are more likely to induce safing than an activity that has been run before. Allowing sufficient time between first time activities and time critical events is prudent. Events such as PIM and PEM, which are repeated many times and are not geometry dependent are not considered key events since they can be rescheduled with minimal impact. Two to six weeks is a reasonable time before most events to recover from safing, perform fault analysis, and redesign and uplink the canceled sequence. Guideline SEQ-G11 Sequence Memory IEB No IEBs in tour should be placed in sequence memory, with the exception of RADAR in normal sequence development Rationale: There is not enough sequencing memory in the CDS non-privileged sequence machine to sequence all of the instrument IEBs in Tour. Since RADAR will be off during S/C uplink periods, RADAR IEBs may be stored in CDS non-privileged memory. Exceptions that would allow other teams to store IEBs in sequence memory may be made on a case-by-case basis at the discretion of the SVTL. Guideline SEQ-G12 Data Volume Margins The following margins should be maintained during sequence planning. Design Product Data Volume Margin Up to end of SOP Implementation 2% Final uplink 1% 3-17

125 The Data Volume Margin is the total additional data volume that can be absorbed and played back within 1 week, expressed as a percentage of the playback capacity within that week. Rationale: The Data Volume Margin as expressed here is precisely that quantity that the Cassini SSR Management Tool computes in version 10.2 and later. These margins are set aside to allow for small changes in telecom performance, downlink pass configuration, DSN scheduling, and sequence planning. They are intended to prevent significant replanning should small changes arise. Larger data volume margins to protect against more significant changes cannot be accommodated since they would result in unacceptable reductions in science observations and increases in DSN requests Spacecraft Pointing Constraint POINT-C1 Spacecraft Articulation Margin Policy TBD. (This constraint will contain the Project s margin policy for turn rates and accelerations on reaction wheels and thrusters. Combined with AACS deliveries of the available raw articulation resources, this will provide all the necessary information for planners to design turns.) Constraint POINT-C4 Prime Instrument One science instrument shall be designated "prime" during science observing time in which the spacecraft pointing is not already determined. An instrument team will specify the spacecraft pointing for the interval in which it is prime. Rationale: The purpose of this constraint is to avoid extra interfaces by defining that there shall be a single instrument that controls pointing during each observation period. The burden of any coupled pointing design rests solely on the instrument teams themselves. Constraint POINT-C5 Prime Instrument Specified Attitude Prime instruments shall leave the spacecraft axes at: Science Planning-specified attitude at the end of their time as a prime instrument. Rationale: The Science Planning Team is responsible for managing and defining the waypoint strategy used for Tour. A waypoint strategy will be adopted that minimizes any unnecessary spacecraft slewing. Constraint POINT-C6 Turns to Targets The SPVT shall be responsible for spacecraft turns when both the target body and prime instrument change. Rationale: Defines who has control of turns Telecommunications Constraint TEL-C1 Cruise DSN Coverage Cruise DSN coverage shall be requested consistent with that specified in the Project Service Level Agreement (PSLA) Rationale: The PSLA is the controlling document for DSN coverage requests. DSN coverage is required for downlink spacecraft telemetry and uplink commands, and to provide navigation data for maneuvers, planetary encounters, conjunctions, instrument checkouts, cruise science, etc. Constraint TEL-C2 Tour DSN Coverage (was a guideline, TEL-G3) An average of one downlink period per day (exclusive of Radio Science passes) shall be scheduled during the tour. Rationale: Consistent with the 15 hour science recording/9 hour downlink operations concept. Provides flexibility in scheduling DSN resources while also constraining their average load. Occultation periods and gravity field flybys generally require two DSN stations for complete coverage of the event. Radio Science geometric experiments which require consecutive DSN passes shall be accommodated on an occasional basis (estimated at ~ one additional pass per month, averaged over the four years of the tour). 3-18

126 Constraint TEL-C9 High Activity Downlink High activity data return shall be calculated assuming one of the following DSN and spacecraft configurations: 1) northern hemisphere 70 meter DSN pass, ranging off, 90% confidence; 2) northern hemisphere 70/34 meter arrayed pass, ranging off, 90% confidence. High Activity passes shall be requested up to 35% of the time. Actual data return shall be accomplished with equivalent performance DSN configurations. Rationale: Specifies the expected data return configuration adequately for planning purposes. Northern hemisphere stations may have different performances (e.g. the Goldstone low noise feed upgrade); equivalent performance implies performance equivalent to whichever station is requested. High Activity days are capable of returning 4 Gbit per day. Constraint TEL-C10 Low Activity Downlink Low activity data return shall be calculated assuming a northern hemisphere 34 meter DSN pass, ranging on, 90% confidence. Actual data return shall be accomplished with equivalent performance DSN configurations. Rationale: Specifies the expected data return configuration adequately for planning purposes. Low Activity days are capable of returning 1 Gbit per day. Constraint TEL-C12 Telemetry Link Confidence Level The Spacecraft Operations Office and the Science Planning Team shall design sequences such that the telemetry link provides the following probabilities of telemetry being successfully received by the ground during the following mission phases or activities: Mission Phase or Activity Probability Level Saturn tour 90 % * Cruise 85 % *Dual playbacks shall be used for critical data and other data as specified in DATA-C4. Rationale: 004 requirement. Constraint TEL-C14 Data Rate Switches and DSN Lockup Data transmitted during initial DSN lockup, data rate switches, and unexpected outages (e.g., bad weather or station problems) shall be assumed to be lost. Rationale: Operations staffs from Cassini and from other missions have indicated that strategies to recover data transmitted during DSN lockup (i.e. at frame sync) and data rate switches are expensive and complicated. DSN lockup is estimated to be ~ ten seconds at kilobit and higher data rates, and data rate switches are expected to take even less time. Due to the low amount of data lost, these strategies are not needed. Constraint TEL-C15 Radio Science Occultation Pass Strategy During Radio Science Occultation experiments, telemetry modulation shall be turned off. Rationale: Telemetry modulation is turned off to increase the signal-to-noise ratio during Radio Science occultation experiments. Constraint TEL-C16 Command Uplink Background sequence design shall not require more than two command uploads per sequence. For each upload, time shall be set aside during the pass for two uplink attempts and one verification period during one pass. Rationale: Breaking up detailed sequences into multiple pieces involves significant ground complications and coordination and should be minimized. Whenever possible, sequences should only require one command upload. 3-19

127 Guideline TEL-G2 Real-time Commands The use of real-time commands should be constrained to those activities which cannot be accomplished via the stored sequence. Rationale: Real-time commands increase cost and risk. Guideline TEL-G5 Length of Downlink Period Downlink periods should be 9 hours in length, unless a longer pass is required to return 4 Gbit on a high activity day or 1 Gbit on a low activity day. Rationale: Restricts planners from overly burdening the DSN by regularly scheduling long passes Management of On-Board Data Constraint DATA-C5 Probe Data Protection Probe relay data shall be dual recorded (the same data recorded on each SSR) and kept stored on-board the orbiter until ground command is received by the orbiter authorizing deletion of the probe relay data. The ground command shall be issued after it has been verified that the correct data has been received at JPL (for data in non-protected partitions in SSR A and B) and at ESOC (for data in protected partitions in SSR A and B). Uplink window opportunities shall be provided after the transmission of probe data to allow data deletion or overwriting from the SSR. The windows shall be scheduled following a TBD (24) hour period on the ground during which data quality is verified. Rationale: Prompt uplink windows following ground receipt of probe data can free up SSR space for post-flyby science collection by releasing the write protection flag. Constraint DATA-C6 Engineering Data Engineering data shall be continuously recorded in all flight sequences. Rationale: Allows the spacecraft health to be tracked and attitude to be reconstructed. Under normal conditions, it is not necessary that all engineering data be downlinked. Constraint DATA-C7 SSR Partition During tour operations, each SSR shall be capable of storing telemetry in at least three partitions. The partition layout of these shall be the same on both SSRs. Rationale: Typically partitions will be needed for engineering (except AACS), science (plus AACS), and OPNAVs and/or high-value science. Identical layouts minimize the chance of problems caused by an unexpected SSR swap. The partition sizes may vary between SSRs but the same partitions must exist. The minimum size for a partition is one frame, or 8800 bits. Constraint DATA-C9 SSR Instrument Data Recording An instrument's data recording shall be monitored by CDS and stopped once the data volume equals the data volume allocation for that instrument. Rationale: Data volumes must be policed to protect all engineering and instrument data allocations. CDS has been identified as the authority best suited to data volume policing. CDS performs data policing via data volume allocations uploaded from the ground with each sequence upload. Constraint DATA-C10 Navigation SSR allocation The navigation data volume allocation for OPNAVs shall be maintained separately from the ISS data volume. Rationale: Navigation data volume allocations will typically supplement the ISS data volume allocation just before the OPNAV is taken. Constraint DATA-C11 SSR Priority Playback Only OPNAVs and probe mission data shall be allowed priority in the playback sequence during the tour, except for post-anomaly diagnostic data retrieval. 3-20

128 Rationale: Prioritized playback of specific instrument data is very difficult as all data are mixed within the science and engineering partition. Neither science nor engineering managers have requested prioritized playback of any specific data, unless a spacecraft fault has occurred. Constraint DATA-C12 High-Value Data High-Value data as specified by a science team or SCO, shall be written into a separate partition on-onboard the spacecraft (but not write-protected). Rationale: Provides additional protection, and permits a science team or SCO to use part of its data volume allocation to protect important data. Constraint DATA-C13 High-Value Data Playback Data selected as high-value shall be played back over two separate DSN passes as executed by the on-board sequence. Thereafter, the data shall be released without the necessity of ground verification of receipt of the data. High value data playback shall be counted within the downlink data allocation of the relevant team for both playbacks. Rationale: Provides additional protection of High-Value Science (or Engineering) Data from accidental loss of DSN coverage on one of two days, loss of all or part of relay from DSN to JPL, inclement weather, etc. Constraint DATA-C14 SSR Playback During Cruise and Tour, all data recorded on the solid state recorders in partitions 4 and 5 shall be played back by the end of the last pass in each sequence. Rationale: Carryover of recorded data is not allowed between sequences to simplify SSR management. (There is no requirement to playback engineering data on partition 6 unless there is an anomaly.) Pre-Saturn Science Activities Constraint PRESAT-C11 Quiet Spacecraft for Radio Science During Cruise During certain Radio Science cruise activities (Gravitational Wave Experiments, GWE Systems Tests, Solar Conjunction Experiments, HGA calibrations, and RSS ICO tests), a "quiet spacecraft" is required and shall be defined as follows: 1) S/C attitude controlled by RWAs and no firings of RCS thrusters or the main engine; 2) No motion imparted to spacecraft by any other instrument (i.e., no articulation, moving filter wheels, etc.); 3) No state changes (includes power changes or transients greater than 28 Watts) and with other disturbances (such as activating and deactivating heaters, transmitters, etc. minimized. Rationale: Radio Science investigations are sensitive to all small forces imparting motion to the spacecraft, including other instruments' motions and state changes. From PRESAT-C6: Reduction of the reaction wheels momentum buildup can be accomplished without thruster use, for instance through 180 degree slow rolls about the Earth line every 10 days. This motion takes care of the momentum buildups for the X- and Y- axes. Calculations show that the Z momentum buildup is slow enough that it does not require unloading within the 40 days of the GWE. From PRESAT-C8: If 28 W of collimated (worst case) thermal radiation changes direction, it can result in a differential translational acceleration over the time scales of interest equal to the goal of requirement Saturn Tour & SOI Constraint TOUR-C1 Activities prior to SOI The following conditions shall apply while the SOI critical sequence is active: a) attitude shall be X-band to Earth, until the start of the turn for the ascending ring plane crossing preceding the SOI burn. The secondary axis shall be between +X to Saturn North Pole and +X to Saturn North Pole -40 degrees (roll about spacecraft Z with +X toward Saturn) b) no spacecraft attitude changes except to support ring plane crossing and the SOI burn. 3-21

129 c) Instruments are quiescent(quiescent means no power state changes, no s/w modifications) -instrument internal sequences, initiated prior to SOI critical sequence activation, may be executing. - instruments may lower their high voltage states prior to the SOI burn from an instrument internal sequence already executing d) no AACS control mode changes e) no real-time commands f) no sequenced bus commands except for engineering commands issued from the critical sequence. Exception: S/C telemetry mode changes (including corresponding subcarrier and mod-index changes) between any RTE&SPB telemetry mode and S&ER- 10 are allowed to execute from the background sequence until 12 hours before the first critical activity executes [about 29 hrs before the SOI burn]) g) during the critical sequence, only one SSR is available, due to the SSR ping-pong bit being disabled Rationale: Defines a Quiet Period before SOI where safing is unlikely due to lack of activity, and allows time to recover from safing if needed. Constraint TOUR-C2 Titan Atmospheric Model Update The Science and Uplink Office shall investigate on the first Titan flyby the Titan atmospheric density and provide a Titan atmospheric model using that data by one month after the first Titan flyby. Rationale: Allows adjustment of Titan flyby altitudes. It is expected that AACS will also conduct an analysis of the controlled response of the first Titan flyby in support of minimum Titan flyby altitude decision. Constraint TOUR-C3 Probe Release at Late Dates Probe release shall not be attempted less than 9 days before Titan encounter. Rationale: Provides sufficient time for emergency maneuvers on failure of Orbital Deflection Maneuver. Guideline TOUR-G1 Post-Separation Imaging of the Probe Images of the Huygens probe should be acquired by both the NAC and the WAC during the time periods from probe separation to probe separation + 1 day and again from ODM to ODM + 3 days. Preferred observation times are probe separation + 1 day and ODM + 3 days. Rationale: Images of the probe after separation can be used to estimate the probe trajectory and adjust the HGA pointing direction for the data relay. They can also be used to determine the probe s approximate orientation for anomaly diagnosis. Images taken shortly after separation can also be used for public outreach Miscellaneous Constraint MISC-C1 (formerly C-44) Checkout of Redundant Hardware Operating subsystems shall not be switched to standby redundant units for status or calibration unless: a) critical sequences require immediate unit switching in response to a failure in the primary operating unit, or b) the spacecraft has experienced a stressful environment (particle hits, etc.) and knowledge of the redundant unit status could substantially affect future plans, or c) one of the following allowed activities: 3-22

130 1) SRU Backup unit, which may undergo yearly performance characterizations. The unit shall not be set to Prime during the maintenance. switching the AACS bus during the BAIL maintenance activity switching the Probe Support Avionics (PSA) unit during Probe operational activities switching to backup UVIS CPU2 during Instrument Checkout as done during ATLO tests operating the backup EGA during periodic maintenance operating the backup RWA during periodic maintenance switching to backup MAG processor/power supply during Instrument Checkout as done during ATLO tests Rationale: Checking redundant units does not save costs or increase mission reliability. Exceptions reflect activities where designed activities are an allowed in-flight repeat of ATLO tests during ICO, activities where SCO has adopted the prelaunch development design which reflects periodic use of the backup unit, and where the activity (BAIL maintenance) requires the use of a separate unit. Constraint MISC-C2 In-Flight Use of Redundant Units Prior to SOI plus 2 years, mission and sequence design shall be based upon the assumption that redundant spacecraft units are not available for the enhancement of mission return, with the exception noted below. The exception is: redundant data storage devices shall be used to capture critical science data and engineering diagnostic data redundantly, and may be used to enhance mission return beginning with sequence C40, 20 October Rationale: Controls use of redundant units to a reasonable level. 3.6 Controlled Scenario Timelines The following scenario timelines are under change control: SOI and Probe Mission. The timelines are repeated on the following pages from the appropriate sections in this document. These timelines are not completely up to date, but are intended only to reflect the last scenario design that was reviewed across the project and subsequently approved via ECR. 3-23

131 SOI Events Timeline Phoebe Targeting TCM bi-prop pressurization SOI-35 Phoebe Flyby SOI-19 d Phoebe Clean-up TCM SOI-15 d Approach Clean-up (if needed SOI-10 d) Saturn Periapsis Activate Critical Sequence Start Quiet Period SOI-8 d Critical Sequence Execution } SOI initial Clean-up SOI+2 d SOI Final Clean-up SOI+15 d Solar Conjunction pre-quiet Period Quiet Period CS post-burn Period Passes per day sequence S1 sequence S2 Day of Year (DOY)

132 HGA to Earth HGA to probe HGA to Earth Orbiter Probe Support Earth, Sun Change to PRLY tlm mode, PSAs ON Turn HGA to Probe (~12 min) Probe at Entry (interface altitude 1270 km) Receive & Record Probe Data Turn HGA to Earth Probe Data Playback (7.86 hrs req'd for both SSRs) SSRs write-protected Orbiter Science Quiet period* begins TCA-8 days All instrument data cleared from SSRs All instruments OFF Science resumes (at most) 2 days after playback (Probe may request additional playbacks) Probe Events Time from TCA Coast Phase -4.0h Probe Entry -2h 6m Cassini-Titan range: km Probe Link (~4.5 hr) Orbiter Closest Approach Probe (TCA) Touchdown 0 Cassini-Titan TCA km Surface Science: S/C will continue to track probe for ~60 minutes (Probe battery life ~ 5 hrs) *Quiet period restrictions: Spacecraft turns and rolls (S/C in RCS mode) Power state changes Engineering configuration changes AACS Mode Changes No quiet period restrictions on: SSR data playback MAPS data collection Cassini/Huygens Probe Relay Timeline

133 Mission Plan Guidelines & Constraints History OPERATIONAL MODES DATA MANAGEMENT OPS-C1 ACTIVE DATA-C1 deleted by ECR OPS-C2 deleted by ECR DATA-C2 deleted by ECR OPS-C3 Changed to guideline G3 by ECR DATA-C3 deleted by ECR OPS-C4 deleted by ECR DATA-C4 deleted by ECR OPS-C5 ACTIVE DATA-C5 ACTIVE OPS-C6 ACTIVE DATA-C6 ACTIVE OPS-C7 ACTIVE DATA-C7 ACTIVE OPS-C8 deleted by ECR DATA-C8 deleted by ECR OPS-C9 deleted by ECR DATA-C9 ACTIVE OPS-C10 deleted by ECR DATA-C10 ACTIVE OPS-G1 deleted by ECR DATA-C11 ACTIVE OPS-G2 deleted by ECR DATA-C12 ACTIVE OPS-G3 deleted by ECR DATA-C13 ACTIVE SEQUENCING DATA-C14 ACTIVE SEQ-C1 deleted by ECR DATA-G1 deleted by ECR SEQ-C2 deleted by ECR , see SEQ-G12 DATA-G2 deleted by ECR SEQ-C3 ACTIVE DATA-G3 deleted by ECR SEQ-C4 deleted by ECR PRE-SATURN SEQ-C5 ACTIVE PRESAT-C1 deleted by ECR SEQ-C6 ACTIVE PRESAT-C2 deleted by ECR SEQ-C7 ACTIVE PRESAT-C3 deleted by ECR SEQ-C8 ACTIVE PRESAT-C4 deleted by ECR SEQ-C9 ACTIVE PRESAT-C5 deleted by ECR SEQ-C10 ACTIVE PRESAT-C6 deleted by ECR SEQ-C11 deleted by ECR PRESAT-C7 deleted by ECR SEQ-C12 ACTIVE PRESAT-C8 deleted by ECR SEQ-C13 ACTIVE, was SEQ-G3 PRESAT-C9 deleted by ECR SEQ-C14 deleted by ECR PRESAT-C10 deleted by ECR SEQ-C15 ACTIVE PRESAT-C11 ACTIVE SEQ-C16 ACTIVE PRESAT-G1 deleted by ECR SEQ-C17 ACTIVE PRESAT-G2 deleted by ECR SEQ-C18 ACTIVE PRESAT-G3 deleted by ECR SEQ-G1 deleted by ECR EARTH SWINGBY SEQ-G2 ACTIVE ESB-C1 deleted by ECR SEQ-G3 changed to constraint by ECR ESB-C2 deleted by ECR SEQ-G4 deleted by ECR ESB-C3 deleted by ECR SEQ-G5 deleted by ECR ESB-C4 deleted by ECR SEQ-G6 ACTIVE ESB-C5 deleted by ECR SEQ-G7 ACTIVE ESB-C6 deleted by ECR SEQ-G8 ACTIVE ESB-C7 deleted by ECR SEQ-G9 changed to constraint by ECR ESB-C9 deleted by ECR SEQ-G10 ACTIVE ESB-C10 deleted by ECR SEQ-G11 ACTIVE ESB-C11 deleted by ECR SEQ-G12 ACTIVE ESB-C12 deleted by ECR POINTING ESB-C13 deleted by ECR POINT-C1 ACTIVE ESB-C14 deleted by ECR POINT-C2 deleted by ECR ESB-C15 deleted by ECR POINT-C3 deleted by ECR ESB-C16 deleted by ECR POINT-C4 ACTIVE ESB-C17 deleted by ECR POINT-C5 ACTIVE ESB-C18 deleted by ECR POINT-C6 ACTIVE ESB-C19 deleted by ECR TELECOMMUNICATIONS TOUR TEL-C1 ACTIVE TOUR-C1 ACTIVE TEL-C2 ACTIVE TOUR-C2 ACTIVE TEL-C3 deleted by ECR TOUR-C3 ACTIVE TEL-C4 deleted by ECR TOUR-G1 ACTIVE TEL-C5 deleted by ECR TOUR-G2 deleted by ECR TEL-C6 deleted by ECR MAIN ENGINE OPERATION TEL-C7 deleted by ECR MEO-C1 deleted by ECR TEL-C8 deleted by ECR MEO-C2 deleted by ECR TEL-C9 ACTIVE MEO-C3 superceded by MEO-C5, ECR TEL-C10 ACTIVE MEO-C4 deleted by ECR TEL-C11 deleted by ECR MEO-C5 deleted by ECR TEL-C12 ACTIVE MEO-C6 deleted by ECR TEL-C13 deleted by ECR MEO-G1 deleted by ECR TEL-C14 ACTIVE MEO-G2 deleted by ECR TEL-C15 ACTIVE MISCELLANEOUS TEL-C16 ACTIVE, was guideline TEL-G1 MISC-C1 ACTIVE TEL-G1 changed to constraint by ECR MISC-C2 ACTIVE TEL-G2 ACTIVE MISC-C3 superceded by MEO-C6 per ECR TEL-G3 deleted by ECR MISC-G1 deleted by ECR TEL-G4 deleted by ECR MISC-G2 superceded by MEO-C6 per ECR TEL-G5 ACTIVE 1 8/10/05

134 Mission Plan Compliance with the Project Policies & Requirements Document Reqt. No. Requirement Title Achieved? Discussion Sec 2 Project Policies and Constraints 22-1D Project Goal Yes The complete Mission Plan addresses this goal by demonstrating a mission design that balances mission success with complexity that could drive cost. A high probability of proper operation is addressed by such aspects of the mission design as (continues) maintaining margins in other consumable budgets, such as gyro and reaction wheel usage; slowly lowering the Titan flyby altitude during the tour; reducing ring plane crossing risk until later in the tour, etc. 22-2D Project Priorities Yes The complete Mission Plan addresses these priorities. While there are no major compromises in the design, examples of these considerations in the scenario development are: minimum payload activity in first year after launch, cautious (continues) approach for the Earth flyby scenario, probe deployment on the first Saturn orbit with a backup opportunity on the second orbit, carefully constrained payload operation near SOI, and so forth. 22-3B Mission Set: primary, backup, and The complete Mission Plan addresses the primary mission. Backup and secondary missions have Yes secondary launch opportunities been defined [2.2] Titan IV/Centaur Launch Vehicle Yes Baseline vehicle is Titan IV/Centaur [3.1, 4.3] Launch Readiness Date Yes Primary mission baseline has earliest launch date on October 6, 1997 [4.3] Cassini End of Mission and End of Project Yes Mission design complies [2.1, ] 23-1 Inertial Reference Frame Yes Mission design and navigation software uses J2000 as the primary reference frame. Sec 3 Science Investigation Objectives 31-1C Pre-Saturn Yes Scenarios for payload operations in the interplanetary mission and the Saturn approach phase support these objectives [5, 6] Saturnian System Yes Scenarios for Saturn system observations from pre-soi through the tour support these objectives [6,7]. 32-1B Orbiter Science Investigations Yes Scenarios for Saturn system observations from pre-soi through the tour support these investigations [6,7] Probe Science Investigations Yes Probe scenario supports these investigations [6.3] En Route Gravitational Wave Experiment Yes Opportunities and plans for gravity wave experiments have been identified [5.5, 6.1] D En Route Solar Conjunction Shown in Cruise timeline (Figure 2.1) and Mission Events Table (Table 2.1); DSN coverage may Yes Experiment need to be added in DMR 322-1B Titan Objectives Yes Plans for Saturn tour will provide many observational opportunities for these objectives [6.3, 7]. Conflicting instrument requirements, such as pointing, power, and data rate will require allocation of observations to certain Titan flybys B Saturn Objectives Yes Plans for Saturn tour will provide observational opportunities for these objectives [6.1, 6.3, 7] B Ring Objectives Yes Plans for Saturn tour will provide observational opportunities for these objectives [6.2, 6.3, 7] B Icy Satellite Objectives Yes Plans for Saturn tour will provide observational opportunities for these objectives [6.1, 6.3, 7] B Magnetosphere Objectives Yes Plans for Saturn tour will provide observational opportunities for these objectives [6, 7] A Reference Operational Modes Yes Reference operational modes have been defined [8] and future scenario work will define the detailed implementation.

135 Mission Plan Compliance with the Project Policies & Requirements Document Reqt. No. Requirement Title Achieved? Discussion 331-2B Jupiter Science (not precluded) Yes Mission design can accommodate limited Jupiter science for the distant flyby, but no firm decision is made, pending better understanding of ground system capability [5.5.3]. Sec 4 Project Derived Requirements Launch Vehicle Resiliency Yes Baseline vehicle is Titan IV/Centaur [3.1,4.3] with fallback mission for SRM [2.2,4.3] Launch Vehicle/Spacecraft Launch sequence shows no unnecessary delay in separation after the injection burn. Separation Yes Separation is planned 10 minutes after MECO-2 [4.4] Contingency Launch Period Yes Eleven contingency launch dates have been defined for the primary mission [4.2, 4.3] Launch Period Duration Yes Baseline launch period for the primary mission is 30 days in duration. Launch periods for the secondary mission (35 days) and the backup mission (18 days) have also been defined. [2.2, 4.2, 4.3] 411-5B Probability of Impact Yes - Prelim Requirement on the Centaur collision/contamination avoidance maneuver to avoid impact with other planetary bodies will be defined in the Target Specification [4.4] C Sufficiently High Parking Orbit Yes Parking orbit altitudes are defined to achieve minimum 10-day lifetime, and a preliminary SHO contingency strategy has been defined to simply the commanding of maneuvers to raise the orbit altitude [4.4] Gravity Assist Yes Trajectory design complies [5.1] Near-SOI Science Yes SOI scenario provides near-soi science observations with relatively small increase in sequence complexity [6.2] Probe Delivery Orbit Yes Trajectory design provides for probe delivery on the first Saturn orbit, and a backup opportunity on the second orbit [6.3] B Probe Data Acquisition Yes Probe relay scenario complies [6.3] Probe Approach Velocity Yes Trajectory design complies; baseline value is 5.75 km/sec [6.3] D Probe Delivery Tracking Yes Probe entry is planned far away from Solar conjunctions [6.3] D Probe Delivery Orbit Yes Probe entry is on an inbound Titan flyby [6.3] Tour Duration Yes Trajectory design complies [7.1] Tour Geometry Requirements No (but mostly) The current reference tour exceeds or complies with most, but not all, of these criteria. Specific trade-offs between the achieve-able geometry and science objectives for the tour will be made in close consultation with the Project Science Group B Titan Flyby Frequency Yes Titan flybys as close as 16 days, but no closer, are planned according to agreed-upon ground system constraints and the TCM spacing is provided [7.1, 7.4] B Satellite Flyby Minimum Altitudes Yes Minimum planned Titan flyby altitude is 950 km. Studies of Titan atmospheric models are continuing. Minimum planned icy satellite flyby is 500 km [7.1, 7.2] B Attitude Control Monopropellant Current hydrazine budget for attitude control activities is 22.1 kg with 3-sigma AACS statistics Yes Allocation and conservative mission assumptions [3.2.3] Mission Scenarios Yes - Prelim Resource operating margins for spacecraft consumables have been allocated [3.2.3], payload operating constraints within the operating modes are preliminary [8.1], ground system margins are not yet worked in detail D Mission Contingency Yes The mission contingency mass is creatable from several potential mission trade-offs including Saturn arrival date, SOI burn delay, initial orbit period, average Titan flyby altitude, etc Ring Hazards Prior to Probe Delivery Yes - Prelim The ring crossings before and after SOI through the F-G gap satisfy this probability based on the risk constraint equation documented in the MRRD [6.2, 7.2].

136 Mission Plan Compliance with the Project Policies & Requirements Document Reqt. No. Requirement Title Achieved? Discussion Environmental Hazards After Probe The tour design meets this requirement via gradual reduction of the Titan flyby altitude and the Yes Delivery ring plane crossing strategy B Uplink Windows Yes - Prelim The Mission Plan is not yet at this level of detail. A mission constraint for uplink windows is defined [8.3] Adequate Tracking and No important events planned within 5-deg SEP. The tour design specifically avoided targeted Yes Communications satellite encounters within 5-deg SEP [7.2] B Operability of Operational Modes Yes - Prelim A preliminary definition and operating strategy for the operational modes have been made, particularly to minimize power and thermal analysis, but only preliminary assessments of the overall operability of the mission have been made [8.1] B Interface Simplicity Yes This guideline has been included in the mission design approach B Operational Power Margins Yes The power analysis used for definition of the operational modes includes 20-Watt operating margin in all power modes with additional margin [8.3] Personnel Holidays Yes SOI and probe mission trajectory design complies [6.2, 6.3] D Earth Swingby Requirements on Mission Design Yes Earth swingby requirements have been included in Section Space-to-Ground Telemetry Link BER Yes Telecom data used for mission design for all mission phases assumes BER no greater than 1.0E D Space-to-Ground Telemetry Link Confidence Level Yes 95% link confidence level used in telecom analysis for all cruise and emergency link calculations. 90% link confidence used for Saturn tour data return predictions. Greater than 95% confi-dence for critical science activities at Saturn will be achieved Ground-to-Space Command Link Error Rate Yes Uplink error rate of 1.0E-9 is achieved by 1.0E-5 telecom error rate and CDS error detection C Maximum Allowable Communications Outage Period Yes Minimum tracking coverage frequency is once per week in cruise [5] Ground-to-Space Command Link Telecom data used for mission design for all mission phases based on 99% uplink link confidence Yes Confidence Level level Redundancy Policy Yes - Prelim No current plans to use redundant units for mission enhance-ments, other than the SSR B Critical Events Yes - Prelim Work on the critical sequences and fault protection is very preliminary B Earth Swingby Yes Mission design studies to support this requirement are documented in the Earth Swingby Plan ( ). Sec 5 Verification D Sequence Validation Yes Operational Scenario Capabilities Yes - Prelim Qualitative Risk Assessment TBD Mission design will provide supporting scenarios for flight sequence testing and for definition of early cruise sequences. This verification will be the continuing role of the Scenarios Working Group, where representatives from science, flight system, and ground system review proposed scenarios. A qualitative risk assessment has not yet been performed for the mission design but, in general, the elements of mission risk are similar to Galileo: long cruise phase with multiple close planetary flybys, probe deploy/relay, orbit insertion maneuver, etc

137 PMISSION PLAN ECR CHANGE LOG ECR SUBJECT APPROVED SECTIONS IMPLEMENTED r1 OpMOde Transition Block Changes 13 April 05 3 Table 1.2,1.5 August 2005 Rev 0 chg OpMode Transition block changes 13 Dec 04 8 Table 1,5 August 2005 Rev 0 chg CDA OpMode Transition block changes 12 Dec 04 3 Table 1,5 August 2005 Rev 0 chg Op Mode Transition Updates for RSS 30 Sept 04 3 Table 1,5 August 2005 Rev 0 chg MP-Data Volume Margin 15 Mar 04 3 August 2005 Rev 0 chg MP-Downlink Pass Block Restriction durng 26 Sept 03 3 October Rev O OTM passes MP-Allow dual SSR use in Cruise 24 Sept 03 3 October Rev O OPMODE transition Block Update 23 Sept 03 3 (Table 8.5) October Rev O MP-Delete Obsolete Guidelines; Add Data 2 July 03 3 October Rev O Constraint for SSR Playback OPMODE Definition Update 9 May 03 3 October Rev O MP-1st time use of Instrument Commands 6 Mar 03 3 October Rev O PMS Flight Rules Clean-up 24 Feb 03 2 (5.5.2) October Rev O MP-Sequence Memory IEB 13 Jan 03 3 October 2003 Rev O MP-SSR Lobrary Region Update 9 Dec 02 3 October 2003 Rev O Opmode Transition Block Mods 16 Sept 02 3 October 2003 Rev O MSS D9.0 New IVP and Movable Block 5 Sept 02 2 October 2003 Rev O Sequence Regions MP-SSR CD Library Allocation Restriction 19 Dec 01 3 October 2003 Rev O SOI Constraints 13 May 02 8 May 2002 Rev N OpMode Changes 27 Mar 02 8 May 2002 Rev N Mission Plan Constraints 9 Jan 02 8 May 2002 Rev N Conjunction Restrictions 9 Jan 02 8 May 2002 Rev N Dual SSRs 31 Oct 01 8 May 2002 Rev N Mission Plan Timeline Update 14 May 01 8 June 2001-Rev M Updates to MP Guidelines and Constraints 9 May 01 8 June 2001-Rev M Tour Data Rate Selection 31 October 00 8 June 2001-Rev M Quiet S/C for Radio Science during Cruise 23 August 00 8 June 2001-Rev M Change to Definition of Critical Data 2 August 00 8 June 2001-Rev M Reusuable Sequence Constructs 18 July 00 8 June 2001-Rev M PSLA Update 25 June 00 Table J.2 10 July 2000-Rev L VIMS Stellar Calibration 26 May 00 5 (add to text) 10 July 2000-Rev L Tour Downlink Strategy 16 May July 2000-Rev L Tour Downlink Durations 16 May July 2000-Rev L Tour Arrayed Passes 16 May July 2000-Rev L DSN PSLA update 8 Feb 00 Table J.2 26 Jan 2000-Rev K Deletion of Table Jan 00 Table Jan 2000-Rev K Change Timing of GWE Test 19 Jan 00 Section 5 26 Jan 2000-Rev K Operational Mode Definitions 5 Aug 99 Table Jan 2000-Rev K Telemetry Mode Changes 14 July 99 Table Jan 2000-Rev K

138 4.0 SELECTED REFERENCE PROJECT POLICY REQUIREMENTS (FROM 004) The following is a list of requirements from the Project Policies and Requirements document that are still active, relevant and may need to be checked by Mission Planning. Design requirements and pre-launch requirements have been removed Near-SOI Science. The Mission Design shall be capable of acquiring science data at Saturn closest approach in a manner that does not compromise reliably achieving Saturn orbit B Probe Data Acquisition. The Mission Design shall provide for probe data acquisition for 180 minutes from entry into Titan's atmosphere D Probe Delivery Tracking. The Mission Design should place Probe entry at least 45 days after and at least 10 days before solar conjunction Tour Geometry Requirements. The Saturnian orbital tour shall include the following: a) 10 orbits with a Saturn periapsis 250,000 km. b) 1 Saturn magnetotail excursion, apoapsis 40 R s and within 3 R s of the Sun-Saturn line, night side. c) 4 close ( 10,000 km) targeted flybys of icy satellites including Enceladus and the dark side of Iapetus, with a goal of 4 additional non-targeted icy satellite flybys to 30,000 km. d) Saturn inclinations 50 for ring observations and 2 occasions with large differences in solar incidence angles. e) Saturn and Titan phase angle range from 0.1 to 175. f) Saturn and Titan latitude and Saturn inclinations well distributed from approximately 0 to 85. g) A minimum of 21 Titan passes. h) A minimum of 25% of the Titan passes suitable for RSS occultation measurements at a range of latitudes (range 50,000 km). i) 6 Titan low altitude passes ( 1,000 km or as dictated by safety) j) Solar, Earth and stellar occultations of Saturn, Titan, and rings distributed in latitude, longitude, ring opening angle, and dayside/nightside coverage B Titan Flyby Frequency. The Mission Design shall not schedule spacecraft flybys of Titan closer than 16 days, or TCM executions closer than -3 days and +2 days of every Titan encounter B Satellite Flyby Minimum Altitudes. The Mission Design shall not include Titan flyby altitudes lower than 950 km (or as compatible with revised Titan atmosphere models and the risk limits of 416-4), or icy satellite flyby altitudes lower than 500 km B Attitude-Control Mono-Propellant Allocation. Mission Design shall design the overall mission profile and scenario level of attitude-control activities (including reaction wheel unloading) to not require more than 40 kg of hydrazine at the 95% probability level Ring Hazards Prior to Probe Delivery. Given that the Spacecraft is functioning properly at 1 day before SOI, the probability of delivering the Probe to its prescribed relay link envelope shall be 99.7%, insofar as ring particle hazards are concerned Environmental Hazards After Probe Delivery. For a minimum of one year following Probe Mission Completion (PMC), both Orbiter risk and the probability of mission redesign shall be controlled. For non-catastrophic environmental hazard events (those associated with the ring environment and the Titan atmosphere leading to temporary performance degradation), each of the above two risk factors shall be 5%. For catastrophic environmental hazard events (those leading to permanent loss of function), the risk factors shall each be 1% B Control of Activities Associated with a Geometric Event. The COS shall be able to time commands to control activities associated with closest approach for Saturn, Titan, and targeted icy satellite flybys with the following accuracies. 4-1

139 Target Titan and targeted icy satellites Saturn (for Titan inbound orbits) Saturn (all other orbits) Timing Accuracy 3 sec (1 sigma) TBD sec (1 sigma) 2 sec (1 sigma) Instrument Resource Allocation Violations. The COS shall not correct instrument resource allocation violations, except to allow replacement, if schedule permits, or to delete the violating observations from the sequence B Sequence Design Throughput Time. The COS shall require no longer than 10 weeks (goal 5 weeks) to design and implement four-week-duration sequence loads B Sufficient Navigation V. The COS Navigation function shall ensure a probability of 0.95 of being able to correct for navigation flight path errors (stochastic plus bias-related for Earth swingby) through EOM. This requirement shall be met for a V allocation that does not exceed 500 m/s (less 10 m/s for each Titan encounter fewer than 35 total encounters) for the bipropellant system, and that does not exceed 50 kg for the monopropellant system Target-relative Pointing Prediction. The COS shall be capable of providing the following ephemeris-related 99% radial pointing prediction accuracies: a) 2.2 mrad of the apparent direction of the Earth for RSS Ka-band occultation experiments. b) 2.4 mrad relative to Titan, icy satellites, up to 10 orbiting "rocks", and features in Titan's and Saturn's atmospheres for CIRS at > 30,000 km c) 3.1 mrad relative to Titan, icy satellites, up to 10 orbiting "rocks", and features in Titan's and Saturn's atmospheres for ISS, VIMS, UVIS at > 20,000 km Target-Relative Pointing Reconstruction. The COS shall be able to reconstruct targetrelative pointing at ranges 10,000 km to 2.0 mrad, 95% radial, in cases where support imaging ("C-smithing") is not utilized D Radar Target-Relative Pointing Control. The COS shall provide a total pointing control of the Ku-Band electrical boresight, relative to the target's center of mass, 95% radial, with spacecraft inertial pointing accuracy capability as specified in D, as follows: a) In the scanning radiometry mode: 17 mrad. This requirements refers to Titan, Saturn and the other satellites. b) In the scanning altimetry mode (low resolution) at Titan at altitudes from ~ 25,000 km to ~ 10,000 km: 17 mrad. c) In the nadir pointing altimetry mode (high resolution) at Titan: 8 mrad at 10,000 km and 17 mrad at 4,000 km. d) In the imaging modes (low resolution and high resolution) at Titan at altitudes < ~4,000 km: 50 mrad. e) During radiometric calibrations: 3.5 mrad. f) During spotlight mode: no requirement Inertial Pointing Reconstruction. The COS shall reconstruct the history of the pointing of the instruments relative to inertial space to an accuracy of 1.1 mrad, 95% radial, for the narrow angle camera D Radar Target-Relative Pointing Reconstruction. The COS shall provide a total pointing reconstruction accuracy of the Ku-Band electrical boresight relative to the target's center of mass, 95% radial, of 1.7 mrad with spacecraft inertial pointing reconstruction accuracy capability as specified in B Reconstruction of Time of a Geometric Event. The COS shall reconstruct the time of closest approach to Saturn, Titan, and targeted icy satellites with an accuracy of 300 msec (1 sigma) Anomaly Priority. Except for critical events (see ), the resolution of any major spacecraft-related anomaly shall take precedence over other activities. 4-2

140 5.0 MISSION PLANNING PROCEDURES 5.1 CONSTRAINT CHECK FOR SEQUENCE PHASE ON DATE This procedure performs a end-to-end check of the mission-level activities and requirements, including DSN passes, navigation tracking and maneuver strategy to ensure that the basic sequence structure can safely support maneuvers and encounters. This procedure should be exercised at two stages: at SOP Implementation and SOP Update. The full textual procedure should be conducted near the beginning of each phase, and the Excel checklist should be filled out at the end. 5.2 How to Obtain Sequence Information and Reports You should be able to find the ap_downlink text, nav, check, SMT report and SPASS on the SP home page for the sequence. The SPASS is also available in CIMS. Be prepared to refer to the other, following documents available as follows. The MP home page: the Mission Plan and the CIRS/VIMS consumables page, and the latest tour events list; the Procedures folder: this document, the RSS DSN plan, the DSN weekly maintenance plan, and the Excel MP checklist template; at the DSN major downtimes schedule. Write down the sequence start and end time of the sequence from the Mission Plan. Also write down who the SP and SVT leads are for your sequence Navigation Review N1) Identify all maneuvers from the navigation events in CIMS (not the DOWNLINK_PASS events with OTP ). Refer to the DSN report or CIMS and ensure that for each maneuver, there is a primary and backup downlink pass that have consistent times, are at least 9 hours long, and are no more than a day apart. Verify that only one downlink pass is present for each maneuver (even for splitcomplex passes; SEQ-C18). N2) Check that the primary contains the string OTP in the downlink pass name and the backup contains OTB. Check that the gap time, which is the first parameter of the downlink pass, is 01:22 for the primary pass only. N3) Determine if there are any nontargeted flybys of any rocks less than 20,000 km (refer to John s latest tour events timeline). With the latest trajectory, determine the actual flyby distance (e.g. with digit). Contact the navigation team to determine if there is any chance of hitting this body. N4) Examine the ap_downlink nav report for skipped days, i.e. days with no navigation tracking, or days with insufficient nav tracking ( NO s). If two parts of a handover pass combine to 5:50, and each segment is 2 hours or longer, this is acceptable. N5) Inspect the balance of Madrid / Goldstone coverage. There should be on average 1 Madrid pass every 9 days. Also, there should be at least 4 passes between targeted encounters (for short orbits, fewer than 4 may be acceptable). N6) Check the OPNAV events or data volume to ensure that no more than 8 OPNAVs have been scheduled on any one day (SEQ-G2), and that the data volume is no greater than 8.7 Mbit per OPNAV (SEQ-C13). 5-1

141 N7) Identify all RSS events in the sequence and ensure that none impact nav tracking in a way that the ap_downlink nav report cannot illustrate (e.g. USO PIM). N8) Provide the nav team with a copy of the nav report whether or not there are any problems, and review any issues identified above Dust Crossing Review H1) Identify all dust hazards within the sequence from the tour events table or Dust Protection Plan (not from the sequence). These are NOT ring plane crossings. H2) For all hazards which require HGA to RAM pointing, ensure there is an MP event present that ends in _PRIME in CIMS. The event should start no later than 5 minutes before dust ingress and end no earlier than 5 minutes after egress (5 minutes is margin). H3) Refer to the SPASS and check that the orbiter is on HGA to RAM point for the entire duration of the crossing. (CDA may have negotiated slight offsets from this attitude for data collection with John Smith on a case by case basis.) H4) For all crossings (including HGA to RAM crossings), refer to the sequence to check that the main engine cover is closed before and opened after the crossing. Check that the cover is open during all primary or backup maneuver passes DSN Review D1) Examine the DSN pass lengths. If a significant number of passes are longer than 9 hours, find out why. In general, it is less burdensome to the DSN to schedule a 9 hour 70m pass than a 11 hour 34m pass (i.e. if we need the data volume, we should upgrade, not lengthen; TEL-C2, TEL-G5). D2) Study the messages in the ap_downlink report check report to discern where passes conflict with DSN weekly maintenance by more than 1-2 hours. Conflicts with 34m stations can be solved by hopping to another 34. Conflicts with 70m stations may be resolved by carrying over into the next segment, using a 70m on another day, moving the pass to use the 70 at another complex, using a 34m array, or using a 70 or 70/34 array outside of the maintenance period, but keeping a 34 from the main complex up the entire time (for tracking). Work with the SP lead or the TWT that owns the pass to determine a solution. D3) Look for handover passes. Consider changing these to one-complex passes if possible (i.e. if they do not conflict with weekly maintenance). D4) Refer to the RAP home page ( for major downtimes that have been approved. If any downtimes fall within your sequence, check to see if station requests conflict with the major downtimes, If so, work whatever data volume or other issues arise from that station being unavailable. D5) Net data margin should be 2% or greater at all times by the end of SOP, and 1% or greater by final uplink (SEQ-C2, DATA-C14). If the margins are too low, upgrade coverage as necessary to raise the margins to an acceptable level. D6) If there are any special playbacks planned during the sequence (e.g. for highvalue data, as with SOI, Probe Relay, Ta), check that CDS has thoroughly reviewed the playback strategy and commanding and it has been or will be tested in ITL (DATA-C12, C13). D7) Check the Mission Plan for conjunctions during your sequence. Check the SPASS to ensure that the spacecraft is at Earth-point when SEP 3 (SEQ-G6). Check that there are no downlink passes when SEP 2 (SEQ-C15). However, there should still be daily DSN passes during the entire conjunction period. 5-2

142 D8) Check the SPASS or CIMS for prime radio science activities (i.e. occultations, gravity or mass events). Compare the DSN resources requested against those listed in the Radio Science DSN request document to ensure they are consistent. Ensure that telemetry will be off for occultations (i.e. no downlink pass; TEL-C15). Work any potential mismatches with an RSS representative. D9) Inspect the balance of 34m / 70m coverage. Over a sequence no more than 35% of the passes should require a 70m station (RSS passes do not count). If the ratio is significantly more than 35%, understand why and determine if the ratio can be reduced easily while maintaining acceptable margins (TEL-C9). D10) Check that the last four downlink passes in a sequence are marked SEQ (unless the last pass has a maneuver, in which case it is superceded by OTP ). All but the last pass must be at least 9 hours long and be free of maneuvers. Look at the nav report to verify that uplink begins 10 minutes after the start of pass in each case. If not, there may be a transmit limit that reduces the uplink time contact the SVT lead for your sequence to determine what impact that may have. D11) Check to ensure that no DSN passes are only for real-time commands (SEQ-C8). D12) Identify the first uplink pass and write down the epoch of the start of the pass. Contact the SVT lead for the sequence and/or Vickie Barlow. Check that the SSUP process is scheduled consistently with the uplink time. D13) Understand and work other errors identified by ap_downlink report check (TEL-C9, C10) Wrap-up (end of phase) W1) Fill in the Excel MP and Nav checklists (Jim may do the Nav checklist for each sequence) and document any issues you have identified in the comment areas and in the SPLAT table. Send the worksheet electronically to the SP lead(s) for your sequence and review with them issues you have identified. W2) Find out what CIRS/VIMS consumables are used during the sequence, and ensure the CIRS/VIMS home page is up to date. Let Kim know if you make any changes in case she has to request a reassessment of the whole-tour usage. 5-3

143 5.2 DSN PLAN FOR SEQUENCE PHASE ON DATE This procedure reviews the DSN schedule for a sequence, updates it, and prepares the report to be sent to the DSN schedulers for final mid-range scheduling of the sequence. The output product is an electronic file containing all DSN requests, along with a spreadsheet of additional notes for the sequence. The schedule should be fully mature, and changes after this delivery should be discouraged. This procedure should be executed after SOP implementation, some weeks before Aftermarket begins, about 33 weeks before start of execution. The MP lead should work closely with the SP lead to ensure that the schedule is as accurate as possible. Be prepared to refer to the following documents available as follows. The SP sequence page: the SMT and DSN reports, and SPLAT; the MP home page: the Mission Plan; the Procedures folder: this document, the RSS DSN plan and the DSN weekly maintenance plan; at the DSN major downtimes schedule. Scheduling S1) At least two weeks before your DSN plan due date, contact the DSN scheduler and verify the actual due date for the DSN schedule. Depending on their schedule, and where the sequence lies, you may have more time than you think. Also, perhaps only the first few days of the sequence are required at first. S2) Contact the SP lead and make him/her aware of the DSN schedule date and that all DSN coverage issues need to be resolved. S3) Contact the RSS rep (Aseel) to make him/her aware when their inputs are due DSN Review D1) Review the SPLAT with the SP lead for any items that are related to DSN coverage. Decide on a course of action and implement these changes, either in CIMS, or in a temporary sequence file used to generate DSN requests. D2) Net data margin should be 2% or greater at all times by the end of SOP implementation, and 1% or greater by final uplink. If the margins are too low, upgrade coverage as necessary to raise the margins to an acceptable level. If margins seem unnecessarily high, consider only if resources are ample downgrading passes. Look especially for 70/34 arrays that could be downgraded to single-antenna passes to reduce risk. D3) Inspect the latest downtimes on against your notes from the previous sequence; check to ensure that no major downtimes have changed. D4) Look for any passes in your sequence, or in the next sequence, that have a configuration that has not been used for a long time (3 months or more; e.g. Canberra, array). Consider adding one or more shadow passes in the weeks before the event to ensure DSN proficiency. D5) Work any other DSN-related warnings or errors produced by ap_downlink RADIO SCIENCE REQUESTS R1) One week before the DSN plan is due, obtain the RSS requests. Make sure they are in seg format. Run ap_downlink report check on the requests to make sure they are formatted correctly and there are no glaring errors. R2) Review the requests and ensure they are consistent with the RSS DSN scheduling guidelines (at end of procedures). Understand what each request is for. 5-4

144 R3) If any RSS activities are changed and affect navigation tracking, contact the Nav team to ensure that the change is acceptable. R4) Add the passes to the sequence via ap_downlink ingest paste. Produce Output Report and Publish O1) Run ap_downlink report faster on the sequence to generate the raw data file. O2) Inspect the configuration codes in the report. Look for zeros that need fixing; review RSS passes with an RSS team member to ensure the codes are correct. Make sure RSS ORT passes are listed as best efforts only and only the primary passes are requested (no _b passes). O3) Create a notes worksheet in excel from the DSN PLAN template. Use the SMT report to add notes appropriate to data volume margins. Determine which 70m passes are crucial for science return vs. those that could fall a day earlier or later. O4) Review the DSN passes with the navigation team and determine which maneuvers are especially large, time-critical, or compromised. Make notes in the spreadsheet as appropriate. Determine if any passes are especially critical for tracking and also make notes as appropriate. O5) Finish off the notes for each pass and review the spreadsheet with the SP lead. O6) Publish the raw data file and spreadsheet to the DSN scheduler, SPVT lead, and the RSS team member if radio activities are present. Review the products to ensure they understand their meaning. Send a full seg file to the SPVT lead so they may bring CIMS up to date. 5-5

145 5.3 DSN INGESTION FOR SEQUENCE PHASE ON DATE This procedure obtains the official, fully negotiated DSN schedule for a sequence, and determines the impacts of any changes on the sequence. This procedure should be executed about one week before the start of SOP Update. The MP lead should work closely with the SP lead to understand any impacts to the sequence DSN Ingestion D1) Check the DOM to see if a DSN file has been posted by the schedulers; if not, contact the schedulers and request one for the sequence. D2) Review the delivered passes versus the requested schedule and note all deviations. D3) If deviations could cause reductions in data playback, ask the SP lead to ingest the new schedule via ap_downlink ingest update, hand-edit the downlink passes as needed, recomputed the data rates via ap_downlink recomputed downlink, and rerun SMT to determine the impact. You can perform this instead depending on the relative workload and personalities of you and the SP lead. D4) If the new schedule will cause data loss, and the SP lead agrees that the schedule should be upgraded, contact the DSN scheduler to try to renegotiate the pass(es) in question. D5) Contact an RSS team representative if any of their passes have changed. 5-6

146 5.3.2 RSS DSN Scheduling guidelines Definitions: RSS science passes = occultations and gravity passes (including Nicole s new Ka-band gravity requests) - non-science includes ORTs, engineering passes, boresight cals, etc. everything else RSS will submit complete sets of requests per sequence to MP by one week before MP's submission to the schedulers - any activities that affect data playback should have been fully worked with SP - assumes MP provides accurate submission schedule, and accurate playback schedule is available from CIMS RSS science passes are to be scheduled to the fullest ability of MP/DSN - changes shall be submitted and worked whenever they are discovered - changes after submission to schedulers are discouraged, but will be accepted Non-science passes are to be scheduled on a best-efforts basis by MP/DSN - no changes will be entertained after submission to the schedulers (except reductions, deletions and configuration details which do not affect playback, nav tracking or start/stop times) - shall not overlap DSN weekly maintenance (up to 1 hour conflicts are OK) - no risk to boresight cals and USO tests as they lie in existing playback passes One or two ORTs, per RSS science activity are to be requested - if the DSN is performing well after the first few months of RSS science, future ORTs should be reduced/released One or two of new Ka gravity supports per sequence, on average, are to be requested DSN requests are submitted to the schedulers only by Mission Planning up to the end of SOP Update - configuration details which do not affect playback, nav tracking or start/stop times can be worked directly with the schedulers RSS reported ~ 100+ ORT passes and ~ 40 new Ka gravity support for the tour. If these numbers should be exceeded, these guidelines will be reevaluated. 5-7

147 CIMS activity decoder ring (refer to CIMS activity types for true reference) OBSERVATION_PERIOD SP_RRRNA_DDDOBSNNN###_NA where RRR = rev number of start epoch, DDD = complex and antenna of following downlink pass (e.g. G34), NNN = notes field DOWNLINK_PASS DSN_PASS SP_RRREA_DDDDDDNNN###_PRIME where RRR = rev number of start epoch, DDDDDD = antenna and complex (e.g. G34BWG, M70MET, G70ARR, C34HEF), NNN = notes field (NON for no notes, or SEQ for sequence boundary pass, OTP for primary OTM pass, OTB for backup OTM pass, CLS for MEA cover closes, OPN for MEA cover opens, RSS for radio science pass, etc.), ### = DOY of start epoch. parameters: gap time in hh:mm:ss (time off-earth for OTMs), DSN lockup time at start of pass in seconds where SSR playback pauses, data rate change time in mid-pass in seconds where SSR playback pauses, then 6 parameters which determine the SSR playback partition order, then up to 5 pairs of modes and epochs which define the telemetry rates during the pass. default: 00:00:00, 300, 60, SSRAP5, SSRBP5, SSRAP4, SSRBP4, SSRNULL, SSRNULL, [modes & epochs] default for OTM primary: 00:00:00, 300, 60, SSRAP5, SSRBP5, SSRAP4, SSRBP4, SSRNULL, SSRNULL, [modes & epochs] SP_RRRNA_DDDDDDNNN###_NA parameters: DSS ID code, precal time, postcal time, DSN label, DSN config code, ignore, ignore, ignore, ignore, ignore, ignore, ignore. default: [DSS ID}, 3600, 900, TKG PASS, N00X,,,,,,, 0 5-8

148 6.0 SATURN SYSTEM MYTHOLOGY Until the middle of the nineteenth century, the satellites of Saturn bore numerical designations only. In 1847, John Herschel proposed that the satellites be named after Saturn s brothers and sisters, the Titans and Titanesses. Titans and Titanesses were brothers and sisters not of Saturn, but of Kronos, Saturn s Greek counterpart. Hesiod, Homer s younger contemporary, gives us the family history of the tribe of the Titans. Using some of Hesiod s own words, here is an outline of the story. In the beginning, there was Chaos, and after him came Gaia (the Earth). Gaia s first-born was Ouranos (the Sky), the one who matched her every dimension. Gaia lay with Ouranos, and bore him Okeanos, Koios, Krios, Hyperion, Iapetus, Theia, Rhea, Themis, Mnemosyne, Phoebe, and Tethys. Her youngest-born was the devious-devising Kronos, most terrible of her children. Hesiod assigned the name Titans to the enumerated twelve children. Kronos, upon urging from Gaia, attacked his father Ouranos with the sickle she provided. Following the attack, Kronos became the supreme ruler of the world. Kronos took Rhea as his wife. She bore him five children. Remembering the fate of his father, Kronos swallowed each child right after it was born. Zeus was the sixth-born. To save the baby, Rhea tricked her husband into swallowing a stone instead. At some later point, Kronos was made to regurgitate the stone and the five children he swallowed. (Hesiod does not say when and how.) With his siblings help, Zeus initiated a rebellion against Kronos and the Titans. The Titans suffered a defeat in a terrible battle during which all earth was boiling. Zeus imprisoned the defeated gods in Tartaros, a moldy place, at the uttermost edges of the monstrous earth and, along with his Olympian allies, assumed the lordship over the world. Although Kronos rule passed, it was long remembered as the Golden Age of mankind, when people lived as if they were gods, their hearts free from all sorrow, without hard work or pain. Saturn, a Latin deity perhaps associated with farming, received some of the attributes of Kronos. The Romans adopted also the legend of the golden age. In their version, Saturn was the king of Italy in the long forgotten days when, as in the age of Kronos, life was all play and no work. John Herschel gave the name Titan to the moon of Saturn which was discovered first and which happened to be the largest. The other four moons discovered in the seventeenth century he named Iapetus, Rhea, Dione, and Tethys. The minute inner satellites first observed by his father, John Herschel chose to name Enceladus and Mimas. Two satellites found in the nineteenth century received the names of Hyperion and Phoebe. The remaining satellites known at present were discovered in the twentieth century. They include Janus, Pan, Atlas, Prometheus, Pandora, Epimetheus, Telesto, Kalypso, and Helene. Of the eighteen named satellites, only Iapetus, Rhea, Tethys, Hyperion, and Phoebe bear the names of Saturn s brothers and sisters, the Titans and Titanesses. A brief description of the meaning of the satellites names is given below. The satellites are listed in the order of the increasing distance from Saturn. Pan (pan) Half-goat, half-human, the Arcadian Pan was worshipped as the patron of shepherds and as the personification of nature. Atlas (AT-less) Son of Iapetus. After the defeat of the Titans, Zeus ordered Atlas, at earth s uttermost places, near the sweet-singing Hesperides to uphold the vault of the sky. Hesiod refers probably to the Pillars of Hercules, the edge of the world known to the ancient Greeks Prometheus (pro-mee-thee-us) 6-1

149 Hesiod presents Prometheus, son of Iapetus, as an immortal who sided with the mortals and as a prankster who liked to annoy his cousin Zeus. The ultimate annoyance was stealing the far-seen glory of weariless fire and giving it to mankind. For this, Zeus fastened Prometheus to a mountain in the Caucasus, and he let loose on hin the wing-spread eagle, and it was feeding on Prometheus imperishable liver, which by night would grow back to size from which the spread-winged bird had eaten in the daytime. Pandora (pan-dor-ah) The world s first woman. Creating Pandora was the punishment Zeus meted out to mankind for the Prometheus brazen acts of disobedience. Pandora arrived equipped with a jar that contained all the misfortunes, curses and plagues. Once the lid was lifted, the evil asserted itself in the world. Hope was the only spirit that stayed there, in the unbreakable closure of the jar, this was the will of the cloud-gathering Zeus. Epimetheus (epp-ee-mee-thee-us) Son of Iapetus, brother of Prometheus, husband of Pandora. Pictured as weak-minded, he is the one who lifted the lid on the Pandora d jar. Janus (JANE-us) An exalted Roman god, a figure of great antiquity and obscure origin. Always represented as having two faces, one looking forwards, the other backwards, Janus presided over the past, present, and future, over gates, doorways, entrances, and beginnings in general, and over war and peace. At every sacrifice, in every prayer, he was the first god invoked, taking precedence before Jupiter. When war was declared, the portals to the sanctuary of Janus on the Forum were opened. They were shut again on the declaration of peace. During the entire history of Rome, this happened on a handful of occasions only. As the most ancient of kings, Janus is supposed to have given the exiled Kronos a warm welcome in Italy, and to have offered him a share of the royal duties. Mimas (MY-muss) One of the Giants, children of Gaia born of the blood of Ouranos. Methone (me-thoe'-nee) Another one of the Alkyonides, a daughter of Alkyoneus. Pallene (pa-lee'-nee) One of the Alkyonides, the seven beautiful daughters of the Giant Alkyoneus. When their father was slain by Heracles, they threw themselves into the sea, and were transformed into halcyons (kingfishers) by Amphitrite. Enceladus (n-sell-uh-duss) One of the Giants, children of Gaia born of the blood of Ouranos. Giants, the last race of Hesiod s monsters, were beings of enormous size and invincible strength. Later depictions show them as having hideous faces, bristling beards, hanging hair, skins of wild animals for garments, tree trunks for weapons, and twin serpents for legs. Tethys (TEE-thiss) The youngest of Titanesses, Tethys married her brother Okeanos, and bore him three thousand Okeanides, the light-stepping sea-nymphs, and as many Rivers, the murmurously running sons. Telesto (tell-ess-toe) A daughter of Tethys and Okeanos, an Okeanide. 6-2

150 Calypso (kal-ip-so) A daughter of Tethys and Okeanos, an Okeanide. For Homer and other authors, she is a daughter of Atlas. In the course of the Odysseus tortuous return to Ithaca, his ship ran aground on the fabled island of Ogygia, the home of the lonely Kalypso. Odysseus kept her company for seven years, after which he departed on a jointed raft. Dione (die-oh-nee) Dione presents a problem in the genealogy of the Greek gods. To Hesiod, she is a daughter of Tethys and Okeanos, and thus an Okeanide. She is mentioned in a number of other incarnations; for instance as a daughter of Ouranos and Gaia (this would make her a Titaness), or as a daughter of Kronos, or of Atlas. In some localities she was also worshipped as the wife of Zeus (instead of Hera). Helene (heh-leen) The divinely beautiful wife of Menelaos, the king of Sparta, Helen (Helene) was abducted by Paris, the son of Priam, the king of Troy. Over Helen the Greeks fought the all-destructive Trojan War. Polydeuces (pol'-i-dew'-seez) Another name for Pollux, one of the twin sons of Leda who was impregnated by Zeus disguised as a swan. He and his brother Castor are known as the Gemini, Latin for twins. Polydeuces was known as a boxer and won many Olympic events. He was also one of Jason's Argonauts on Jason's quest for the golden fleece. During the quest, Polydueces proved himself by killing an evil king and allowing the quest to continue Rhea (ree-uh) A Titaness, married to her brother Kronos. Titan (TIE-tan) Not a single deity, but a generic name for the children of Ouranos and Gaia. Hyperion (high-peer-ee-on) The fourth-born Titan, Hyperion took for a wife his sister Theia. Theia brought forth great Helios and shining Selene, the Sun and Moon, and Eos the Dawn who lights all earthly creatures and the immortal gods who hold the white heaven. Solar and lunar deities, dominant in the affairs of other ancient civilizations, played a minor part in the religious life of ancient Greels. Iapetus (eye-ap-eh-tuss) Iapetus, a Titan, took Klymene, his niece, the light-stepping daughter of Okeanos, to be his wife. Their sons were Atlas, Prometheus, and Epimetheus. Phoebe (FEE-bee) Phoebe, a Titanness, bore to her brother Koios the goddess Leto, the gentlest of all who are on Olympus. Leto, who had lain in the arms of Zeus, bore Apollo and Artemis, children more delightful than all the other Olympians. In later antiquity, Phoebe was honored as the goddess of the Moon. L. Roth, 8 Aug

151 CASSINI AND HUYGENS, THE SCIENTISTS The seventeenth century appears to us as an epoch of gallant manners, lavish costumes, comical wigs, and incomprehensible wars -- all without much relevance to the present. Yet the seventeenth century, despite its remoteness and extravagance, was a time of towering significance. Modern science was born in the seventeenth century and it was in the seventeenth century that mankind's view of the cosmos underwent the most drastic change since the beginning of recorded history. Giovanni Domenico Cassini ( ) and Christiaan Huygens ( ) were two of the learned men of that tumultuous period who, by showing to the incredulous public the new wonders of the sky, helped to usher in the age of science and alter our perception of the world. Giovanni Domenico Cassini Christiaan Huygens. Both Cassini and Huygens came from well-to-do families -- one in Italy, the other in Holland, both received the best education available, both were extraordinarily industrious, and both did most of their lives' work in Paris, as members of the Royal Academy of Sciences established in 1666 by Louis XIV, the fabled Sun King. Huygens earned the invitation to join the Academy and the associated Royal Observatory as a result of having discovered Titan (the first of a number of moons of Saturn to be discovered subsequently) and the rings of Saturn. Before joining the Academy, Huygens also invented the pendulum clock, the first accurate timekeeping device. While still in Italy, Cassini gained fame by having measured the rotation periods of Jupiter and Mars, and by virtue of his extensive observations of the motions of the moons of Jupiter. (The moons of Jupiter were discovered by Galileo some fifty years earlier.) At Paris, Cassini extended his meticulously precise observations to Saturn, discovering four more moons -- Iapetus, Rhea, Dione, and Tethys, and also discovering a gap in the rings of Saturn, later named the Cassini Division. Towards the end of his life, Huygens returned to Holland where he continued to do pioneering work in mechanics and optics. Cassini stayed at 6-4

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