Spacecraft Bus / Platformand more massive than the Sun (delta Scuti and rapidly oscillating Ap...

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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

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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Rømer (1999-2003)

Top-down methodology

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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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.

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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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

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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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

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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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.

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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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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Payload

PropulsionThrusters

Communication

PowerThermal

Shield

Rømer (1999-2003)

PropulsionThrusters

Shield

Communication

PowerThermal

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ADCS:Attitude DeterminationAnd Control Subsystem

Shield

Communication

PowerThermal

CDH:Command andData HandlingSubsystem

PropulsionThrusters

ADCS:Attitude DeterminationAnd Control Subsystem

Shield

Communication

PowerThermal

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29 p/cm10 3

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Payload

PropulsionThrusters

Communication

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

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,

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

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Payload

PropulsionThrusters

Communication

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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Spacecraft

Perturbations, Pointing, SlewNo. of wheels, orientation, Speed, mass-ratio

Impulsmomentog inertimoment

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Spacecraft attitude

AttitudeDetermination

AttitudeControl

ControlDeterminationAttitude

Attitude controltorque

Attitudesensor

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Inertimoment

Cylinder:

Impulsmoment

2SS RM

2WW rm

2SWS rm

1ωL L0

Attitude Control

RMωω

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Attitude Control

RMωω

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

Spacecraft Bus / Platformand more massive than the Sun (delta Scuti and rapidly oscillating Ap...

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