1 COROT Science Week, Berlin, 10-12 December 2003 Agenda Corotweeks' progress reports Operational...

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


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


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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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=



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



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



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


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


Torb < 6 s


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)



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)



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)




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


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


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)



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)



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


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



Scenario against Sun blinding

Toward r.a < 0

Line of nodes

Summer

Winter

Autumn



Central Program 2





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



Scenario against Sun blinding

Toward r.a > 0

Line of nodes

Summer

Winter

Autumn



Central Program 2





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



Eclipses

Line of nodes

Summer

Winter

Autumn



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



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



Rotations of solar wings

Line of nodes

Summer

Winter

Autumn



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)



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



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



Cosmic Rays

Cosmic Rays

(Électrons & protons)

Ions

Solar flares


0

50

100

150

200

1985 1990 1995 2000 2005 2010

Su

n S

pot

Nu

mb

er

22nd 23rd

Sun Activity


Mission



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



Electrons with energy > 4.2 MeV



Protons with energy > 50 MeV



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


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


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 %

1 COROT Science Week, Berlin, 10-12 December 2003 Agenda Corotweeks' progress reports Operational...

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