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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
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 %