Planetary Landers, Entry Probes and Penetrators

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1 Planetary Landers, Entry Probes and Penetrators Dr Andrew J. Ball Alpbach, 2012 Alpbach, 1995

2 Some Benefits of In Situ Investigation 1. Measurements that are impossible remotely a. Many environmental parameters, physical properties b. Detailed composition (trace elements, isotopic, ), petrology c. Measurements hindered by the atmosphere 2. Validation of measurements or inferences from remote investigations, modelling, lab simulation, etc. 3. Scales much finer than achievable remotely 4. Interaction with the environment (active techniques) 5. Sampling of material for in situ analysis 6. Access to sub-surface (sampling, thermal meas., etc.) 7. Mechanical coupling for seismology & rotation meas. 8. Sampling for return to terrestrial labs

3 Mission Architecture vs. Size of the Challenge More challenging science requirements and the practical limitations of instrumentation more ambitious measurement requirements and/or more complex mission architecture Simplest concepts include: Short duration Flyby only Destructive impact / entry Low data return / v. simple measurements

4 Greater complexity / cost arises from: Survival in extreme / poorly known environments (high T, low T, P, radiation, high g, surface topography, material properties) More complex mission operations, e.g.: control architecture targeting / navigation challenges More configuration changes of the spacecraft Multiprobe / network missions Lower technology readiness (TRL scale) More stringent planetary protection requirements Mobility requirements

5 Some Important Things to Worry About 1. Power (solar vs. nuclear vs. primary batteries at Jupiter; nuclear vs. primary batteries further out) 2. Communications a. Relay or Direct To Earth (DTE)? b. Two-way or one-way? c. If relay, where is the orbiter? 3. Probes are generally preprogrammed to surface the long descent destinations are too far away to make commanded operation attractive (long-lived balloons a possible exception) a. Interaction almost always desirable once probe is on the ground 4. Thermal Design a. linked to choice of power source b. RHUs needed? 5. Atmospheric Entry a. Heat shield mass 6. Parachute Descent (& inflation of balloon envelope, if applicable) 7. Encountering the surface 8. Mobility (mechanisms, robotic arms, roving, digging, ) 9. Making sure the lifetime is aligned with the time needed for achieving the objectives

6 Types of Surface / Atmosphere Probe 1. End-of-Mission Impactors a. usually destructive! 2. Atmospheric Entry Probes a. not driven by surface requirements 3. Pod Landers a. don t mind which way up they hit the surface 4. Legged Landers a. need to land the right way up, usually with retros 5. Payload Delivery Penetrators a m/s, c.f m/s for soft landers 6. Minor Body Surface Missions a. don t necessarily need to land, low g

7 India: + Chandrayaan-2 China: Chang'e II Japan: Hayabusa/ MINERVA Europe: Huygens Beagle 2 Philae ExoMars US Other: Pioneer Venus Galileo NEAR US Mars: Viking Landers Pathfinder MPL/DS-2 MER Phoenix MSL Programme Surveyor 1-7 Apollo Ranger 3-5 Soviet Luna Phobos 1,2 Mars 96 Phobos-Grunt Soviet Venera/VeGa Launch date

8 Giant Planet Entry Probes Deep gravity wells high entry speeds large amounts of KE to lose Whether entering prograde, polar or retrograde makes a significant difference If targeted by parent spacecraft, avoidance manoeuvre needed trade-off between targeting precision and saving propellant High speed entry then parachute descent entry science much more restricted than descent science Choice of ablative TPS materials is limited How to (delta-)qualify the TPS? Atmospheric profiles needed to model entry and descent and help determine critical parameters for heatshield, g-loads, parachutes, timing, etc. To what pressure (/depth) do you need to go? Can you get the radio signal out? Some atmospheric species at high pressures absorb at wavelengths used for radio transmission.

9 Entry Probes for Jupiter Galileo Probe (NASA mission) Entered Jupiter s atmosphere in 1995

10 Parachute Deployment Sequence - example

11 Payload Instruments kg entry mass 2. Last transmissions 61.4 min after entry interface point, 3. Payload (28 kg, 26 W) a. ASI atmospheric-structure instrument (Seiff) b. NMS neutral mass spectrometer (Niemann) c. NEP nephelometer (Ragent) d. LRD lightning and radioemissions detector (Lanzerotti) e. HAD helium abundance detector (von Zahn) f. NFR net-flux radiometer (Sromovsky) g. EPI energetic-particles instrument (Fischer) h. DWE Doppler wind experiment (Atkinson)

12 Pioneer Venus Large Probe NASA

13 Huygens: Titan Atmospheric Entry Probe

14 Titan Mare Explorer (TiME) 1. Candidate for NASA Discovery programme

15 Titan Mare Explorer (TiME)

16 Titan Mare Explorer (TiME)

17 Titan: Landers, Balloons? Titan Montgolfières (hot air balloons) use waste heat from RTG to heat the atmosphere in a balloon envelope Probes and balloons end up on the surface at the end of the mission Where to target? Engineering constraints; scientific interest

18 Landers for Large Icy Satellites 1. Europa Lander studied, e.g. see workshop in Moscow 2. Enceladus also studied since Tiger Stripe plumes discovered 3. Low T and (for Europa) high radiation dose 4. Deploy from a. hyperbolic approach from heliocentric orbit? b. hyperbolic approach from planetary orbit? c. orbit around the satellite? 5. Significant uncertainties in small-scale topography and mechanical properties of surface materials pertinent to landing dynamics 6. Otherwise, essentially like landing on the Moon! a. Main braking burn b. Vernier engines c. Doppler radar d. Vision-based guidance for landing?

19 Landing on a Large Airless Moon Example of NASA s Surveyor Landers Cruise attitude Pre-retro manoeuvre 30 mins before touchdown to align main retro with flight path Main retro start by altitude-marking radar which ejects from nozzle. Craft stabilized by vernier engines 60 miles, 6100 mph (96 km, 2730 m/s) Main retro burnout and ejection. Vernier engines control descent ft, 240 mph (7.6 km, 107 m/s) Vernier engines shut down 13 ft, 3.5 mph (4 m,1.5 m/s) J. Garry

20 Landers for small Icy Satellites 1. Giant planet systems are targetrich environments a. e.g. the Saturnian system has 62 (known) moons much diversity 2. Somewhat like landing on a cometary nucleus? 3. Large (~10-30%) payload mass fractions achievable Phobos 1988

21 Philae Comet Lander for Rosetta MPG/DLR

22 Penetrators Uses the ground (as opposed to propulsion, parachutes, etc.) for terminal deceleration Some heritage for Mars and the Moon: Mars 96, DS-2 Mars Microprobes, Lunar-A Some ESA-funded technology developments since early 90s for Mars and Europa Subject to uncertainty of properties of the target at the impact site May be viable as a demonstration payload, or fly many to assure survival of the minimum number needed?

23 Inflatable braking device (IBD) Solid rocket motor Antenna IBD cover Mars 96 Penetrators Instrumentation compartment Aftbody Umbilical tether Forebody NPO Lavochkin

24 Penetrators (3) DS-2 Mars Microprobes NASA

25 Planetary Protection 1. Solar System missions are categorised according to the COSPAR system for planetary protection 2. See 3. See also 2012 NRC Report, Assessment of Planetary Protection Requirements for Spacecraft Missions to Icy Bodies. 4. Limits on bioburden; sterilisation techniques

26 Measurement Categories Geodesy / tracking Space physics Atmospheric physics profiles Aerosol physics Fluid physics Sub-surface sounding Surface physical properties Imaging Photometry & spectrometry Microscopy Chemical composition Mineralogical & elemental composition Sample analysis Sample return

27 Payload Mass Fractions 1000 Luna 16,20,24 Luna 17, Viking Landers Venera 9-14, VeGa 1,2 guesses Payload Mass /kg 10 Phobos 2 PROP-F Phobos DAS Philae Galileo Probe MPL Mars 96 Small Stations Beagle 2 Pioneer Venus Large Probe Huygens Phoenix MPF Surveyor Mars 2,3,6,7 assuming 12kg p/l MSL 16% 8% Mars 96 Penetrators 4% Pioneer Venus Small Probes MER (excl. arm) Mass at Separation /kg

28 Some Possible Trends? Network science (geophysics, meteorology) Astrobiology Mobility (across & below surface) Bulk properties tracers Wider international participation / co-operation Lower frequency of missions Higher data rates / volumes More narrowly focused objectives Importance of landing site selection Sampling and sample return More exotic / extreme target environments Exoplanets / comparative planetology Money-limited Exploration context Establishment of programmes More precise measurements of the same targets / Focus on data quality Narrow objectives for smaller missions only

29 References / Bibliography 1. Ball, A. J., Garry, J. R. C., Lorenz, R. D. and Kerzhanovich, V. V., Planetary Landers and Entry Probes. Cambridge University Press, Wilson, A. (ed.), Huygens: Science, Payload and Mission. ESA SP-1177, Special Issue on Huygens, Space Sci. Rev. 104(1), Special Issue on Huygens, Nature 438(7069), Brown, Lebreton and Waite (eds), Titan from Cassini-Huygens. Springer, Dougherty, Esposito and Krimigis (eds), Saturn from Cassini-Huygens. Springer, Russell, C. T. (ed.), The Galileo Mission. Reprinted from Space Sci. Rev. 60(1 4). Kluwer, Young, R. E., Smith, M. A. and Sobeck, C. K., Galileo probe: in-situ observations of Jupiter s atmosphere, Science, 272(5263), , Young, R. E., The Galileo probe mission to Jupiter: science overview. J. Geophys. Res. 103(E10), , Lorenz, R. D., Planetary Penetrators: Their Origins, History and Future. Adv. Space Res. 48(3), , Planetary Mission Entry Vehicles Quick Reference Guide 12. Martinez Pillet et al. (eds), Payload and Mission Definition in Space Sciences. Cambridge University Press, Kemble, Interplanetary Mission Analysis and Design. Springer-Praxis, TiME publication? 15. Penetrator books / papers / slides 16. NRC SSB report coming out soon 17.