Agenda

1. Agenda 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

2. Progress reports Agenda of Corotweeks (since 2001) Vienna (09/2001) Overview of the mission constraints First proposal for an orbit plane drift Paris (05/2002) « PROTEUS Evolution » upgrades AOCS preliminary simulation campaign Liege (12/2002) Progress report of instrument development Efficiency of baffle against straylight Marseille (06/2003) Optimization of performances in the flight domain Telescope design and optics performances 10/2001 System key point 04/2002 TelescopePDR 04/2003 Equipment Bay CDR 06/2003 Satellite contract 10/2003 SystemPDR web pages at http://smsc.cnes.fr/COROT

3. Progress reports Agenda of Corotweeks Berlin (12/2003) Focus on the orbit and its environment On-board data processing & software design Proposal for 2004 Orsay Progress report of instrument development after CDR AOCS performances after satellite PDR Granada Overview of the Corot Mission Center Ground data processing 11/2003 Software PDR 01/2004 Satellite PDR 03/2004 Payload CDR Start of integration 04/2004 Mission Center PDR 11/2004 RIS Beginning of system tests

4. Operational orbit Mission constraints Long 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 kmpreferred 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

5. North South Operational orbit Mission constraints Straylight 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 CCD Orbit plane Sun boresight g Roll angle Perpendicular to the orbit plane

6. Operational 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)

7. Operational 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 • W = 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

8. Operational orbit Evolution of orbital parameters Semi-major axis (a) decrease < 5 km due to atmospheric drag Torb < 6 s

9. Operational orbit Eccentricity (e) Naturally frozen

10. Operational orbit Inclination (i) Variation of 0.01 deg/an due to luni-solar attraction

11. Operational orbit Right ascension of the ascending node () Parabolic variation < 1 deg/an due to J2 and luni-solar attraction

12. Operational orbit Variation of  with / without maneuvers Variation of Wwithout DV Variation of Wwith DV = 0.5 m/s every 6 months

13. Available for propulsion V round 100 m/s Housekeeping & maneuvers' strategy Commissioning phase semi-major axis (a) : Correction to reach the operational altitude Launcher dispersion : 10 km inclination (i) & right ascension () : Correction on inclination if necessary Launcher dispersion : i < 0.1 and < 0.2° V = 14 m/s Mission phase semi-major axis (a) : No correction Phase properties helpful as engineering tool but not needed for mission Risky maneuver with open cover inclination (i) & right ascension () : Corrections for housekeeping replaced by drift maneuvers V < 2 x 13 m/s End of life Decrease of perigee for re-entry into the atmosphere IADC recommendation V = 60 m/s (allocated)

14. Environment & troublemakers Sun blinding The 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)

15. Environment & troublemakers Variations of the border dates with depointing 190 170 150 No depointing 130 alpha +10 deg Angle (degrees) 110 alpha -10 deg 90 6 months Summer eye (galactic center) delta +10 deg 70 delta -10 deg 50 30 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

16. Zs- Zs- Ys+ Xs+ Ys+ Xs+ Environment & troublemakers 180° rotation on Zs Scenario against Sun blinding Toward eye center Spring Line of Equinoxes Line of nodes Satellite axes in a fixed orbital reference frame ROF 1a 2b Summer Earth orbit Solar declination up to +23° Central Program 1 Central Program 2 Center (18h50) Anticenter (6h50) S ZOF YJ2000 XJ2000 XOF Winter Exploratory Programs 1 & 2 Solar declination down to –23° 1b 2a Equatorial plane 12.5° Autumn 180° rotation on Zs

17. Zs- Zs- Ys+ Xs+ Ys+ Xs+ Environment & troublemakers 180° rotation on Zs Scenario against Sun blinding Toward r.a < 0 Spring Line of Equinoxes Line of nodes Satellite axes in a fixed orbital reference frame ROF 1a 2b Summer Earth orbit Solar declination up to +23° Central Program 1 Central Program 2 Center (18h50) Anticenter (6h50) S ZOF YJ2000 XJ2000 XOF Winter Exploratory Programs 1 & 2 Solar declination down to –23° 1b 2a Equatorial plane 12.5° Autumn 180° rotation on Zs

18. Zs- Zs- Ys+ Xs+ Ys+ Xs+ Environment & troublemakers 180° rotation on Zs Scenario against Sun blinding Toward r.a > 0 Spring Line of Equinoxes Line of nodes Satellite axes in a fixed orbital reference frame ROF 1a 2b Summer Earth orbit Solar declination up to +23° Central Program 1 Central Program 2 Center (18h50) Anticenter (6h50) S ZOF YJ2000 XJ2000 XOF Winter Exploratory Programs 1 & 2 Solar declination down to –23° 1b 2a Equatorial plane 12.5° Autumn 180° rotation on Zs

19. Environment & troublemakers Eclipses Spring Line of Equinoxes Thermal shock on solar wings Perturbation on the line of sight for 20 s Line of nodes Eclipses Summer Earth orbit Solar declination up to +23° No eclipse No eclipse S ZOF YJ2000 XJ2000 XOF Winter Solar declination down to –23° Eclipses Equatorial plane 12.5° Autumn

20. Environment & troublemakers Eclipses (over the year)

21. Environment & troublemakers Rotations of solar wings Spring Every 10 / 15 days for power budget Perturbation on the line of sight for 240 s Coupled with LED calibrations (1 hour) Line of nodes Summer Earth orbit Solar declination up to +23° S ZOF YJ2000 XJ2000 XOF Winter Solar declination down to –23° Equatorial plane Line of Equinoxes 12.5° Autumn

22. Environment & troublemakers Moon blinding Angle between Moon and COROT eye center

23. Environment & troublemakers Moon blinding Distance between Moon and line of sight always > 15° up to 2008always > 10° up to 2010 Risk of blinding if wrong direction Trajectory of the Moon 18h 6h 12h Anticenter Center

24. Environment & troublemakers Solar flares (Électrons & protons) Ions

25. 200 Sun Activity 150 100 Sun Spot Number 50 22nd 23rd 0 1985 1990 1995 2000 2010 2005 Environment & troublemakers Mission

26. Lens Loss of Ion Scintillation Transmission Ionization + + - + - - + - Oxide Oxide + - - + - + - + Trapped - + - + - + - + charges Dysfunction, glitches + - + Atomic - + + - Singular Interface Dose Effects + - - + Silicon Silicon traps Displacements - + + + Effects Component lifetime detectors Contribute to duty cycle detectors Gammas Ions Protons Protons Electrons Oxide interstitial Solar Flares Cosmic Rays Radiation Belts vacancy Silicon Increase of detector dark currents Environment & troublemakers Optics Electronics

27. Environment & troublemakers Electrons with energy > 4.2 MeV

28. Environment & troublemakers Protons with energy > 50 MeV

29. Environment & troublemakers SAA crossed by 4 ascending & 4 descending orbits / dayMean time : 9 min at flux > 300 p+/cm2/s Glitches Seismology channel : Correct data up to 3000 p+/cm2/s Exoplanet channel : Correct data up to 300 p+/cm2/s On-board accumulations interrupted by TC for 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

30. Environment & troublemakers

31. Duty cycle Interruptions in the data : decrease of S/N and ringing in the Fourier spectrum(as soon as an observing run is started) Mission requirements 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 < 10 % < 20 % Events outside of observing runs (maneuvers, station acquisition operations, heavy calibration on demand…) are not taken into account

32. Duty cycle Budget of unavailability Astero channelExo channel 5 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 % Total2.66 % 9.95 % 16.25 % < 10 % < 20 %