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Spacecraft Bus / Platform
Payload
PropulsionThrusters
CDH:Command and DataHandling Subsystem
ADCS:Attitude Determinationand Control Subsystem
Communication
Structure andMechanisms
PowerThermal
Shield
Hubble Space Telescope
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2000 rad / år
Rad, Gray (Gy), Rem, Sievert… mange forskellige enheder
Sievert (Sv) bruges generelt i forbindelse med stråledoseri f.eks. A-kraftværker.
rem = rad x Q, hvor Q ~ 1 for røntgen-, gamma- og betastråling ogQ ~ 5 for protoner og neutroner og Q ~ 20 for alfastråling.
100 rem = 1 Sv = 1000 mSv
Så
mSv = rad X Q / 10
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2000 rad / år= 1000 mSv / år (protoner)
50% dødelighed ved 4000 mSv
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30-100 rad / år= 15-50 mSv / år
50 mSv / år svarer til folk som arbejderved en reaktor kerne
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Space Payload Design and Sizing
Requirements Specifications
Interface Control Document (ICD)
Mission Objective and Critical mission requirements
1. Payload Objectives (Nyttelastens formål)2. Payload Subject Trades (Specifikke krav og håndtering
af nyttelastens formål)
3. Payload Operations Concept (end-to-end, all phases)4. Required Payload Capability5. Identify Candidate Payloads6. Candidate Payload Characteristics7. Evaluate Candidate and Select a Baseline8. Assess Life-cycle Cost and Operability9. Payload-derived Requirements
10. Documentation!
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Mission Objective and Critical mission requirements
Rømer (1999-2003)
Top-down methodology
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 tounderstand physics under extreme conditions, by studying oscillations in a sample of 20 solar-typestars.
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Mission Objective and Critical mission requirements
Example:
Rømer secondary mission objectives
1. To study the structure and evolution of stars hotterand more massive than the Sun (delta Scuti andrapidly oscillating Ap stars) by measuring theiroscillations.
2. To study variability in a large sample of starsof 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)
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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)2. Payload Subject Trades (Specifikke krav og håndtering
af nyttelastens formål)
Example:
Rømer PRS (Payload Requirements Specification)• PRS-01: The main data from MONS should be differential photometry• PRS-02: 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 400 - 520 nm, with amean wavelength of 460 nm.
• PRS-05: Red filter: the passband should be 620 - 780 nm, with amean wavelength of 700 nm.
Things that the spacecraftwill interact with
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Mission Objective and Critical mission requirements
1. Payload Objectives (Nyttelastens formål)2. Payload Subject Trades (Specifikke krav og håndtering
af nyttelastens formål)
Example:
Rømer PRS (Payload Requirements Specification)• PRS-10: We specify 32 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 avoidsaturation (see PRS-18).
• PRS-11: The ACS power spectrum should be flat below 10 mHz anddrop between 10 mHz to 10 Hz by a factor of more than100 in amplitude (10000 in power).
• PRS-19: Fine structure (intrapixel/subpixel): a white noise withpeak-to-peak of 1-2 %
• PRS-20: Over scales of a few pixels (4-10 pixels): 4-5 % (peak-to-peak• PRS-21: Over large scales: non-symmetric structure….. -- 28 PRS
Mission Objective and Critical mission requirements
1. Payload Objectives (Nyttelastens formål)2. Payload Subject Trades (Specifikke krav og håndtering
af nyttelastens formål)
3. Payload Operations Concept (end-to-end, all phases)
Example:
Rømer Operations ConceptMONS Science Data Centre (pipeline reductions):Level 0: Raw CCD images (Operations Team, mission evaluation)Level 1: Raw time series data + HK Level 2: Calibrated dataLevel 3: Oscillation amplitude spectraLevel 4: Extracted frequencies, amplitudes, mode-life times background
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Mission Objective and Critical mission requirements
1. Payload Objectives (Nyttelastens formål)2. Payload Subject Trades)
3. Payload Operations Concept (end-to-end, all phases)4. Required Payload Capability5. Identify Candidate Payloads6. Candidate Payload Characteristics7. Evaluate Candidate and Select a Baseline
Rømer BaselineStar Trackers
Field Monitor
MONS Telescope+ sunshield
CDU – downlinkMomentum W
MolniyaACS req.
Mission Objective and Critical mission requirements
1. Payload Objectives (Nyttelastens formål)2. Payload Subject Trades (Specifikke krav og håndtering
af nyttelastens formål)
3. Payload Operations Concept (end-to-end, all phases)4. Required Payload Capability5. Identify Candidate Payloads6. Candidate Payload Characteristics7. Evaluate Candidate and Select a Baseline8. Assess Life-cycle Cost and Operability
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Mission Objective and Critical mission requirements
1. Payload Objectives (Nyttelastens formål)2. Payload Subject Trades (Specifikke krav og håndtering
af nyttelastens formål)
3. Payload Operations Concept (end-to-end, all phases)4. Required Payload Capability5. Identify Candidate Payloads6. Candidate Payload Characteristics7. Evaluate Candidate and Select a Baseline8. Assess Life-cycle Cost and Operability9. Payload-derived Requirements
10. Documentation!
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Baner og perturbationer Orbit PerturbationsBaner og banemanøvre Orbit ManeuveringFysiske forhold i rummet The Space EnvironmentNyttelasten PayloadPlatform The Platform/Bus
ACS (styring) Attitude Determination and ControlEnergi- og termiskdesign Power and Thermal
Opsendelse af satellitter Propulsion Subsystem and LaunchesRummissioner Space ProjectsJordkontrol Ground System
ESA, NASA, DK Space
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Spacecraft Bus / Platform
Payload
PropulsionThrusters
CDH:Command and DataHandling Subsystem
ADCS:Attitude Determinationand Control Subsystem
Communication
Structure andMechanisms
PowerThermal
Shield
Rømer (1999-2003)
PropulsionThrusters
ADCS:Attitude Determinationand Control Subsystem
Shield
Communication
Structure andMechanisms
PowerThermal
CDH:Command and DataHandling Subsystem
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ADCS:Attitude DeterminationAnd Control Subsystem
Shield
Communication
Structure andMechanisms
PowerThermal
CDH:Command andData HandlingSubsystem
PropulsionThrusters
ADCS:Attitude DeterminationAnd Control Subsystem
Shield
Communication
Structure andMechanisms
PowerThermal
CDH:Command and DataHandling Subsystem
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29 p/cm10 3
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Spacecraft Bus / Platform
Payload
PropulsionThrusters
CDH:Command and DataHandling Subsystem
ADCS:Attitude Determinationand Control Subsystem
Communication
Structure andMechanisms
PowerThermal
Shield
Propulsion Subsystem
• Propellant and tank
• Lines, valves
• Engines / Thrusters
Nitrogen (Cold Gas), Hydrazine (N2H4) (Liquid/Chemical), Solid (Powdered Aluminium) or
Ion (Hg, Xe, Cs, Electrostatic)
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Cold Gas System
um/m
T(K) m/s 157v
Nitrogen (m = 28 m(u)), T = 300 K
km/s 0.528
300 m/s 157v
Simplest form of rocket engine. Reliable, very low cost. LowPerformance (heavy)
Liquid Chemical
• V = 1,4 km/s (Hydrazine, N2H4)
• V = 2,36 km/s (Cryogenic, Liquid O2,
H2)
Simpel, reliable, low cost, low performance (Cryogenic: complicated),Toxic(N2H4+N2O4, N2H4+F2), dangerous
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Nitrogen (Cold Gas):Pegasus Attitude Control
Hydrazine (N2H4) (Liquid/Chemical)Thrusters, Space Shuttle
Solid (Powdered Aluminium)Transfer…. (v=2 km/s)
Ion (Hg, Xe, Cs, Electrostatic)SMART-1 (ESA) (v=20-30 km/s)
Solid andLiquid
Cold GasandLiquid
Solid andLiquid
Ion
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Spacecraft Bus / Platform
Payload
PropulsionThrusters
CDH:Command and DataHandling Subsystem
ADCS:Attitude Determinationand Control Subsystem
Communication
Structure andMechanisms
PowerThermal
Shield
Spacecraft attitude
AttitudeDetermination
AttitudeControl
ControlDeterminationAttitude
Attitude controltorque
Attitudesensor
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Attitude Determination and Control Subsystem (ADCS)
• Attitude, Orbit position, Pointing
• Payload RequirementsPointing (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 RequirementsSun Pointing (thermal control, Safe mode)
Pointing During Thrusting
Communications Antenna Pointing
Attitude Control
• Spin StabilizationPassive SpinSpin with precession control (off-axis thruster)Dual Spin
• 3-axis controlSensor: Earth, Sun and/or star sensors
Gyroscopes, magnetometers, antennasTorquers: Gravity gradient, Magnetic, Thrusters
Wheels: Reaction WheelsMomentum Wheels (spinning)Control moment Gyros (fixed speed)
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IL
Spacecraft
Perturbations, Pointing, SlewNo. of wheels, orientation, Speed, mass-ratio
Wheel
Impulsmomentog inertimoment
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Spacecraft attitude
AttitudeDetermination
AttitudeControl
ControlDeterminationAttitude
Attitude controltorque
Attitudesensor
IL
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Inertimoment
Cylinder:
2RM2
1 I
Impulsmoment
2SS RM
2
1ω L
2WW rm
2
1ω L
r m
2W
2SWS rm
2
1ωRM
2
1ωL L0
Attitude Control
2W
2S rm
2
1ωRM
2
1ω
2
2
SW rm
RMωω
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Attitude Control
2
2
SW rm
RMωω
10r
R 100
m
M
4SW 10ωω
Attitude Control
4SW 10ωω
100-1000 Hz 0.01-0.1 Hz
10-100 sec
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KeplerEnvironmentaltests at Ball
Kepler reaction wheels
Kepler Spacecraft Bus
ACS 3-axis stabilized
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Kepler Spacecraft Bus
Kepler reaction wheels Kepler Star Trackers
Kepler reaction wheel