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1COROT Science Week, Berlin, 10-12 December 2003
AgendaAgenda
Corotweeks' progress reports
Operational orbit & its environment (I)
Mission constraints
Reference orbit parameters
Housekeeping & maneuvers
Environment & troublemakers
Duty cycle
Proposal for an orbit drift (II)
Illustrated example
Displays on Corotsky
2COROT Science Week, Berlin, 10-12 December 2003
Progress reportsProgress reports
Agenda of Corotweeks (since 2001)Vienna (09/2001)
Overview of the mission constraintsFirst proposal for an orbit plane drift
Paris (05/2002)« PROTEUS Evolution » upgradesAOCS preliminary simulation campaign
Liege (12/2002)Progress report of instrument developmentEfficiency of baffle against straylight
Marseille (06/2003)Optimization of performances in the flight domain
Telescope design and optics performances
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10/2001System key point
04/2002TelescopePDR
04/2003EquipmentBay CDR
06/2003Satellitecontract
10/2003SystemPDR
web pages at http://smsc.cnes.fr/COROT
3COROT Science Week, Berlin, 10-12 December 2003
Progress reportsProgress reports
Agenda of Corotweeks
Berlin (12/2003)Focus on the orbit and its environmentOn-board data processing & software design
Proposal for 2004
OrsayProgress report of instrument development after CDRAOCS performances after satellite PDR
GranadaOverview of the Corot Mission CenterGround data processing
11/2003SoftwarePDR
01/2004SatellitePDR
03/2004PayloadCDRStart of integration
04/2004MissionCenterPDR
11/2004RISBeginningof system tests
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4COROT Science Week, Berlin, 10-12 December 2003
Operational orbitOperational orbit
Mission constraintsLong duration for central program : 150 days• the line of sight is assigned to keep a constant direction for 150 days• data available and correct at least 90 % of the time • the Sun must remain at more than 90° from the observed field• no occultation by the Earth
Inertial polar circular orbit between 800 and 900 km• inclination i = 90° leads to have a fixed orbital plane• right ascension of the ascending node : = 12.5°
chosen in 2001 by the COROT Sc. Committee
• altitude 896 km preferred to increase telemetry budget (+19 %)upper limit for radiations
Orbit plane drift• if not strictly polar (i=90°+i), the orbit plane drifts at d/dt
272
22
3/a
ieaJdt/d
μ=
5COROT Science Week, Berlin, 10-12 December 2003
Operational orbitOperational orbit
Mission constraintsStraylight from the Earth
• Line of sight at more than = 20° from the Earth limb• Radius of the observation cone : = arccos (R/a) - = 10 °• Flux less than 1 photon/pel/s guaranteed up to 7 °
Roll domain• 20° on the line of sight, after North/South alignment of the solar arrays• Helpful to optimize the projection of the targets onto the CCDSouth
North
Orbit plane
Perpendicular to the orbit plane
boresightRoll angle
Sun
6COROT Science Week, Berlin, 10-12 December 2003
Operational orbitOperational orbit
The sky observed by COROT
11 main stars A, F, G (mv=6)813 secondary stars (mv<9)at least 200 000 candidates for the exoplanet program (mv<16)
0°
30°
60°
90°
120°
150°
180°
210°
240°
270°
300°
330°
0h2h4h6h8h10h12h14h16h18h20h22h
SummerZone of observationcentered at 18h50
WinterZone of observationcentered at 6h50
Galaxy
7COROT Science Week, Berlin, 10-12 December 2003
Operational orbitOperational orbit
Reference orbit parameters• a = 7274 km (altitude =896 km) phase properties (16 days) in
BOL
• e < 0.01 frozen with = 90°
• i = 90 degrees
• = 12.5 degrees (J2000) line of sight at 6 h 50 12 h
Properties
• Torb = 6174 sec 12 exo exposures (16x32 s)
• Ncycle = 223
• Local time : - 4 min / day flybys repeat every 16 days,
with a move back of 64 min
New
8COROT Science Week, Berlin, 10-12 December 2003
7269
7270
7271
7272
7273
7274
7275
mars 2006 mars 2007 mars 2008 mars 2009 mars 2010
Date
demi-grand axe moyen (km)
Evolution of orbital parameters Semi-major axis (a)decrease < 5 km due to atmospheric drag
Operational orbitOperational orbit
Torb < 6 s
9COROT Science Week, Berlin, 10-12 December 2003
Eccentricity (e)Naturally frozen
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0
Ex (x1000)
Ey (x1000)
Operational orbitOperational orbit
10COROT Science Week, Berlin, 10-12 December 2003
Inclination (i)Variation of 0.01 deg/an due to luni-solar attraction
89.99
90.00
90.01
90.02
90.03
90.04
90.05
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Date (années à partir du 01/03/2006)Inclinaison (degrés)
Operational orbitOperational orbit
11COROT Science Week, Berlin, 10-12 December 2003
Right ascension of the ascending node ()Parabolic variation < 1 deg/an due to J2 and luni-solar attraction
12
12.5
13
13.5
14
14.5
15
15.5
16
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Date (années à partir du 01/03/2006)
Ascension droite du Noeud Ascendant (deg)
Operational orbitOperational orbit
12COROT Science Week, Berlin, 10-12 December 2003
Operational orbitOperational orbit
Variation of with / without maneuvers
12.4
12.5
12.6
12.7
12.8
12.9
13.0
13.1
13.2
13.3
1/3/061/5/061/7/061/9/061/11/061/1/071/3/071/5/071/7/071/9/071/11/071/1/081/3/081/5/081/7/08Date
Ascension droite du Nœud Ascendant (deg)
02/04/2006DV0 = 0 m/s
08/10/2006DV1 = 0.63 m/sDi = -0.0048 deg
02/04/2007DV2 = 0.5 m/sDi = -0.004 deg
08/10/2007DV3 = 0.5 m/sDi = -0.004 deg
02/04/2008DV4 = 0.5 m/sDi = -0.004 deg
Variation of without V
Variation of with V = 0.5 m/severy 6 months
13COROT Science Week, Berlin, 10-12 December 2003
Mission phasesemi-major axis (a) :
No correctionPhase properties helpful as engineering tool but not needed for missionRisky maneuver with open cover
inclination (i) & right ascension () :Corrections for housekeeping replaced by drift maneuvers
Housekeeping & maneuvers' strategyHousekeeping & maneuvers' strategy
Available for propulsionV round 100 m/sCommissioning phase
semi-major axis (a) :Correction to reach the operational altitudeLauncher dispersion : 10 km
inclination (i) & right ascension () :Correction on inclination if necessaryLauncher dispersion : i < 0.1 and < 0.2°
V = 14 m/s
End of lifeDecrease of perigee for re-entry into the atmosphereIADC recommendation
V = 60 m/s(allocated)
V < 2 x 13 m/s
14COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Sun blindingThe Sun must stay at more than 90 ° from the line of sight in every run
the movement of the Sun in the spacecraft reference frame determines when to start and stop every run(S)J 2000.(Xs)J 2000 < 0
Summer : Xs = mom+ depointing
Xs= mom+ depointing
Winter : Xs = mom+ 180° + depointing
Xs= mom+ depointing
Files used by Corot Mission Center :(S)J 2000 and (mom ; mom)J 2000 = f(day)
15COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Variations of the border dates with depointing
30
50
70
90
110
130
150
170
190
01/03/06 01/04/06 01/05/06 01/06/06 01/07/06 01/08/06 01/09/06 01/10/06 01/11/06
Date
An
gle
(d
egre
es)
No depointing
alpha +10 deg
alpha -10 deg
delta +10 deg
delta -10 deg
6 monthsSummer eye (galactic center)
16COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Scenario against Sun blinding Toward eye center
Line of nodes
Summer
Winter
Autumn
Solar declinationup to +23°
Solar declinationdown to –23°
Central Program 2
Exploratory Programs 1 & 2
180° rotation on Zs
180° rotation on Zs
Satellite axesin a fixed orbital reference frame ROF
XJ2000
YJ2000
XOF
ZOF
Equatorial plane
12.5°
Earth orbit
Central Program 1
Line of Equinoxes
Xs+
Zs-
Ys+
Zs-
Xs+ Ys+
1b
1a 2b
2a
Center (18h50) Anticenter (6h50)S
Spring
17COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Scenario against Sun blinding
Toward r.a < 0
Line of nodes
Summer
Winter
Autumn
Solar declinationup to +23°
Solar declinationdown to –23°
Central Program 2
Exploratory Programs 1 & 2
180° rotation on Zs
180° rotation on Zs
Satellite axesin a fixed orbital reference frame ROF
XJ2000
YJ2000
XOF
ZOF
Equatorial plane
12.5°
Earth orbit
Central Program 1
Line of Equinoxes
Xs+
Zs-
Ys+
Zs-
Xs+ Ys+
1b
1a 2b
2a
Center (18h50) Anticenter (6h50)S
Spring
18COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Scenario against Sun blinding
Toward r.a > 0
Line of nodes
Summer
Winter
Autumn
Solar declinationup to +23°
Solar declinationdown to –23°
Central Program 2
Exploratory Programs 1 & 2
180° rotation on Zs
180° rotation on Zs
Satellite axesin a fixed orbital reference frame ROF
XJ2000
YJ2000
XOF
ZOF
Equatorial plane
12.5°
Earth orbit
Central Program 1
Line of Equinoxes
Xs+
Zs-
Ys+
Zs-
Xs+ Ys+
1b
1a 2b
2a
Center (18h50) Anticenter (6h50)
Spring
S
19COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Eclipses
Line of nodes
Summer
Winter
Autumn
Solar declinationup to +23°
Solar declinationdown to –23°
XJ2000
YJ2000
XOF
ZOF
Equatorial plane
12.5°
Earth orbit
Line of Equinoxes
Spring
S No eclipse
Eclipses
No eclipse
Eclipses
Thermal shock on solar wings
Perturbation on the line of sight for 20 s
20COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Eclipses (over the year)Eclipses à 826 km
0
500
1000
1500
2000
2500
0 1000 2000 3000 4000 5000 6000
numéro d'orbitedurée totale (sec)
19/01 19/06 22/07 19/12
Favorable period of timeLow-level perturbations
21COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Rotations of solar wings
Line of nodes
Summer
Winter
Autumn
Solar declinationup to +23°
Solar declinationdown to –23°
XJ2000
YJ2000
XOF
ZOF
Equatorial plane
12.5°
Earth orbit
Line of Equinoxes
Spring
S
Every 10 / 15 days for power budget
Perturbation on the line of sight for 240 s
Coupled with LED calibrations (1 hour)
22COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Moon blindingAngle between Moon and COROT eye center
0
20
40
60
80
100
120
140
160
180
mars2006
sept2006
mars2007
sept2007
mars2008
sept2008
mars2009
sept2009
mars2010
sept2010
Angle avec l'axe instrument (degrés)
Soleil vs Axeinstrument
lune vs Axeinstrument
23COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Moon blinding
Distance between Moon and line of sightalways > 15° up to 2008always > 10° up to 2010
Risk of blinding if wrong direction
6h 12h 18h
Trajectory of the Moon
Anticenter Center
24COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Cosmic Rays
Cosmic Rays
(Électrons & protons)
Ions
Solar flares
25COROT Science Week, Berlin, 10-12 December 2003
0
50
100
150
200
1985 1990 1995 2000 2005 2010
Su
n S
pot
Nu
mb
er
22nd 23rd
Sun Activity
Environment & troublemakersEnvironment & troublemakers
Mission
26COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Cosmic Rays Solar Flares Radiation Belts
Ions Protons Protons Electrons
Singular Effects
Lens Scintillation
Atomic Displacements
Loss of Transmission
Gammas
detectorsdetectors
Dose EffectsElectronics
Optics
Increase of detector dark currents
interstitial
vacancy
Oxide
Silicon
Trappedcharges
Interfacetraps
+ + - + - - + - + - - + - + - +- + - + - + - +
Oxide
Silicon
Component lifetime
Ion
Ionization
Dysfunction, glitches
+ - + - + + - + - - +-+ + +
Oxide
Silicon
Contribute to duty cycle
27COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Electrons with energy > 4.2 MeV
28COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Protons with energy > 50 MeV
29COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
Glitches
Seismology channel :Correct data up to 3000 p+/cm2/s
Exoplanet channel :Correct data up to 300 p+/cm2/sOn-board accumulations interrupted by TCfor 4 x 2 x 16 x 32 + 4 x 16 x 32 s
Lens-glass scintillation
20 ph/pel/s at 3000 p+/cm2/s
SAA crossed by 4 ascending & 4 descending orbits / dayMean time : 9 min at flux > 300 p+/cm2/s
30COROT Science Week, Berlin, 10-12 December 2003
Environment & troublemakersEnvironment & troublemakers
31COROT Science Week, Berlin, 10-12 December 2003
Duty cycleDuty cycle
Interruptions in the data : decrease of S/N and ringing in the Fourier spectrumInterruptions in the data : decrease of S/N and ringing in the Fourier spectrum(as soon as an observing run is started)(as soon as an observing run is started)
Predictive events
mission operations
environment (effect of radiations)
Failures with reboot or reconfiguration
payload
bus
Short interruptions
duration < 1 orbit
likely to occur over 5 days
possibly quasi-periodic
Long interruptions
occurring in a 150-day run
Events outside of observing runs (maneuvers, station acquisition operations,heavy calibration on demand…) are not taken into account
< 10 %
< 20 %
Mission requirements
32COROT Science Week, Berlin, 10-12 December 2003
Duty cycleDuty cycle
Budget of unavailability Astero channel Exo channel5 days 150 days 150 days
Predictive events
SAA crossing 0.80 % 0.80 % 7.10 %
Ground station use conflict 0.75 % 0.75 % 0.75 %
Eclipses Entries/Exits 0.54 % 0.54 % 0.54 %
Rotation of solar wings & calibrations 0.45 % 0.45 % 0.45 %
Corruption of data (payload, MM…) 0.12 % 0.12 % 0.12 %
Pole crossing with solar eruptions 0.42 % 0.42 %
Failures with reboot or reconfiguration
Payload (DPU) and Mass memory 4.50 % 4.50 %
Proteus Bus 2.47% 2.47 %
Total 2.66 % 9.95 % 16.25 %
< 10 % < 20 %