Spacecraft Bus / Platform

Transcription

1 Spacecraft Bus / Platform Propulsion Thrusters ADCS: Attitude Determination and Control Subsystem Shield CDH: Command and Data Handling Subsystem Thermal Payload Power Communication Structure and Mechanisms Hubble Space Telescope 1

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5 000 rad / år Rad, Gray (Gy), Rem, Sievert mange forskellige enheder Sievert (Sv) bruges generelt i forbindelse med stråledoser i f.eks. A-kraftværker. rem = rad x Q, hvor Q ~ 1 for røntgen-, gamma- og betastråling og Q ~ 5 for protoner og neutroner og Q ~ 0 for alfastråling. 100 rem = 1 Sv = 1000 msv Så msv = rad X Q / 10 5

6 000 rad / år = 1000 msv / år (protoner) 50% dødelighed ved 4000 msv 6

7 rad / år = msv / år 50 msv / år svarer til folk som arbejder ved en reaktor kerne 7

8 Space Payload Design and Sizing Requirements Specifications Interface Control Document (ICD) Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades (Specifikke krav og håndtering af nyttelastens formål) 3. Payload Operations Concept (end-to-end, all phases) 4. Required Payload Capability 5. Identify Candidate Payloads 6. Candidate Payload Characteristics 7. Evaluate Candidate and Select a Baseline 8. Assess Life-cycle Cost and Operability 9. Payload-derived Requirements 10. Documentation! 8

9 Mission Objective and Critical mission requirements Top-down methodology Rømer ( ) Mission Objective and Critical mission requirements Example: Rømer primary mission objective To provide new insights into the structure and evolution of stars, using them as laboratories to understand physics under extreme conditions, by studying oscillations in a sample of 0 solar-type stars. 9

10 Mission Objective and Critical mission requirements Example: Rømer secondary mission objectives 1. To study the structure and evolution of stars hotter and more massive than the Sun (delta Scuti and rapidly oscillating Ap stars) by measuring their oscillations.. To study variability in a large sample of stars of all types. Mission Objective and Critical mission requirements Example: Scientific aims (Rømer): Properties of convective cores, including overshoot Structure and age of low-metallicity stars Physical properties of stellar matter Stellar helium abundances Effects and evolution of stellar internal rotation Dependence of the excitation of oscillations Surface features Convective motions on stellar surfaces Reflected lights from exoplanets (and transits) 10

11 Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål) Example: Rømer Payload Objectives Photometric precision: We must be able to detect oscillations that have very low amplitudes (1-10 ppm) Temporal coverage: Each primary target must be observed almost continuously for about one month Sky coverage: The science goals require access to the whole sky over the course of the mission Wavelength coverage: Photometry in more than one colour is required for mode identification Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades (Specifikke krav og håndtering Things that the spacecraft af nyttelastens formål) will interact with Example: Rømer PRS (Payload Requirements Specification) PRS-01: The main data from MONS should be differential photometry PRS-0: The main data from MONS should be two-colour broad-band photometry PRS-03: The MONS payload requires high-stability on short time scales and progressively less stability on longer timescales, to match the shape of the intrinsic stellar granulation noise. PRS-04: Blue filter: the passband should be nm, with a mean wavelength of 460 nm. PRS-05: Red filter: the passband should be nm, with a mean wavelength of 700 nm. 11

12 Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades (Specifikke krav og håndtering af nyttelastens formål) Example: Rømer PRS (Payload Requirements Specification) PRS-10: We specify 3 cm as the Telescope diameter and about 17 cm as the diameter of the central obstruction. The detector will be placed out of focus in order to avoid saturation (see PRS-18). PRS-11: The ACS power spectrum should be flat below 10 mhz and drop between 10 mhz to 10 Hz by a factor of more than 100 in amplitude (10000 in power). PRS-19: Fine structure (intrapixel/subpixel): a white noise with peak-to-peak of 1- % PRS-0: Over scales of a few pixels (4-10 pixels): 4-5 % (peak-to-peak PRS-1: Over large scales: non-symmetric structure PRS Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades (Specifikke krav og håndtering af nyttelastens formål) 3. Payload Operations Concept (end-to-end, all phases) Example: Rømer Operations Concept MONS Science Data Centre (pipeline reductions): Level 0: Raw CCD images (Operations Team, mission evaluation) Level 1: Raw time series data + HK Level : Calibrated data Level 3: Oscillation amplitude spectra Level 4: Extracted frequencies, amplitudes, mode-life times background 1

13 Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades) 3. Payload Operations Concept Star (end-to-end, Trackers all phases) Rømer Baseline 4. Required Payload Capability Molniya 5. Identify Candidate Payloads ACS req. 6. Candidate Payload Characteristics 7. Evaluate Candidate and Select a Baseline MONS Telescope + sunshield CDU downlink Momentum W Field Monitor Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades (Specifikke krav og håndtering af nyttelastens formål) 3. Payload Operations Concept (end-to-end, all phases) 4. Required Payload Capability 5. Identify Candidate Payloads 6. Candidate Payload Characteristics 7. Evaluate Candidate and Select a Baseline 8. Assess Life-cycle Cost and Operability 13

14 Mission Objective and Critical mission requirements 1. Payload Objectives (Nyttelastens formål). Payload Subject Trades (Specifikke krav og håndtering af nyttelastens formål) 3. Payload Operations Concept (end-to-end, all phases) 4. Required Payload Capability 5. Identify Candidate Payloads 6. Candidate Payload Characteristics 7. Evaluate Candidate and Select a Baseline 8. Assess Life-cycle Cost and Operability 9. Payload-derived Requirements 10. Documentation! 14

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19 Baner og perturbationer Baner og banemanøvre Fysiske forhold i rummet Nyttelasten Platform ACS (styring) Energi- og termiskdesign Opsendelse af satellitter Rummissioner Jordkontrol Orbit Perturbations Orbit Maneuvering The Space Environment Payload The Platform/Bus Attitude Determination and Control Power and Thermal Propulsion Subsystem and Launches Space Projects Ground System ESA, NASA, DK Space 19

20 Spacecraft Bus / Platform Propulsion Thrusters ADCS: Attitude Determination and Control Subsystem Shield CDH: Command and Data Handling Subsystem Thermal Payload Power Communication Structure and Mechanisms Rømer ( ) ADCS: Attitude Determination and Control Subsystem Propulsion Thrusters Shield CDH: Command and Data Handling Subsystem Communication Thermal Power Structure and Mechanisms 0

21 ADCS: Attitude Determination And Control Subsystem CDH: Command and Data Handling Subsystem Shield Communication Structure and Mechanisms Thermal Power ADCS: Attitude Determination And Control Subsystem Propulsion Thrusters Shield CDH: Command and Data Handling Subsystem Communication Thermal Power Structure and Mechanisms 1

22 310 9 p/cm

23 Spacecraft Bus / Platform Propulsion Thrusters ADCS: Attitude Determination and Control Subsystem Shield CDH: Command and Data Handling Subsystem Payload Communication Thermal Power Structure and Mechanisms Propulsion Subsystem Propellant and tank Lines, valves Engines / Thrusters Nitrogen (Cold Gas), Hydrazine (NH4) (Liquid/Chemical), Solid (Powdered Aluminium) or Ion (Hg, Xe, Cs, Electrostatic) 3

24 Cold Gas System Simplest form of rocket engine. Reliable, very low cost. Low Performance (heavy) Nitrogen (m = 8 m(u)), T = 300 K v 157 m/s T(K) m/m u v 157 m/s km/s Liquid Chemical V = 1,4 km/s (Hydrazine, NH4) V =,36 km/s (Cryogenic, Liquid O, H) Simpel, reliable, low cost, low performance (Cryogenic: complicated), Toxic(NH4+NO4, NH4+F), dangerous 4

25 Nitrogen (Cold Gas): Pegasus Attitude Control Hydrazine (NH4) (Liquid/Chemical) Thrusters, Space Shuttle Solid (Powdered Aluminium) Transfer. (v= km/s) Ion (Hg, Xe, Cs, Electrostatic) SMART-1 (ESA) (v=0-30 km/s) Solid and Liquid Solid and Liquid Cold Gas and Liquid Ion 5

26 Spacecraft Bus / Platform Propulsion Thrusters ADCS: Attitude Determination and Control Subsystem Shield CDH: Command and Data Handling Subsystem Thermal Payload Power Communication Structure and Mechanisms Spacecraft attitude Attitude Determination Attitude sensor Control Determination Attitude Attitude Control Attitude control torque 6

27 Attitude Determination and Control Subsystem (ADCS) Attitude, Orbit position, Pointing Payload Requirements Pointing (Entire payload or a subset of the payload) Pointing Direction (and the reference system) Pointing Range Pointing Accuracy Pointing Knowledge Pointing Stability Slew Rate Exclusion Zones General Requirements Sun Pointing (thermal control, Safe mode) Pointing During Thrusting Communications Antenna Pointing Attitude Control Spin Stabilization Passive Spin Spin with precession control (off-axis thruster) Dual Spin 3-axis control Sensor: Earth, Sun and/or star sensors Gyroscopes, magnetometers, antennas Torquers: Gravity gradient, Magnetic, Thrusters Wheels: Reaction Wheels Momentum Wheels (spinning) Control moment Gyros (fixed speed) 7

28 Impulsmoment og inertimoment Wheel L I Spacecraft Perturbations, Pointing, Slew No. of wheels, orientation, Speed, mass-ratio 8

29 Spacecraft attitude Control Determination Attitude Attitude Determination Attitude sensor Attitude Control Attitude control torque L I 9

30 30 Inertimoment Cylinder: R M 1 I Impulsmoment S S R M 1 ω L W W r m 1 ω L r m W S W S r m 1 ω R M 1 ω L L 0 Attitude Control W S r m 1 ω R M 1 ω S W r m R M ω ω

31 Attitude Control ω W ω S M R m r R M r m ω 4 W ωs 10 Attitude Control ω 4 W ωs Hz Hz sec 31

32 Kepler Environmental tests at Ball Kepler Spacecraft Bus Kepler reaction wheels ACS 3-axis stabilized 3

33 Kepler Spacecraft Bus Kepler reaction wheels Kepler Star Trackers Kepler reaction wheel 33