Key science goals
- Detection of terrestrial exoplanets up to the habitable zone of solar-type stars and characterisation of their bulk properties needed to determine their habitability.
- Characterisation of hundreds of rocky (including Earth twins), icy or giant planets, including the architecture of their planetary system, to fundamentally enhance our understanding of the formation and the evolution of planetary systems.
- These goals will be achieved through:
- planet detection and radius determination (3% precision) from photometric transits;
- determination of planet masses (better than 10% precision) from ground-based radial velocity follow-up,
- determination of accurate stellar masses, radii, and ages (10% precision) from asteroseismology,
- identification of bright targets for atmospheric spectroscopy.
Observational concept
Ultra–high precision, long (at least two years), uninterrupted photometric monitoring in the visible band of very large samples of bright (V≤11-13) stars.
Primary data products
- High cadence optical light curves of large numbers of bright stars.
- Catalogue of confirmed planetary systems fully characterised by combining information from the planetary transits, the seismology of the planet-host stars, and the ground-based follow-up observations.
Payload
Payload concept
- Set of 24 normal cameras organised in 4 groups resulting in many wide-field co-aligned telescopes, each telescope with its own CCD-based focal plane array;
- Set of 2 fast cameras for bright stars, colour requirements, and fine guidance and navigation.
Optical system
6 lenses per telescope (1 aspheric)
Focal planes
104 CCDs (4 CCDs per camera) with 4510 x 4510 18 µm pixels
Instantaneous field of view
∼ 2232 deg², with 4 groups of cameras respectively looking on 301 deg², 247 deg², 735 deg², and 949 deg².
Overall mission profile
Operations reference scenario
Nominal in-orbit science operations with a Long duration observation phase including two single fields monitored for two years each. Optionally a split into 3 years long duration pointing and 1 year “step-and-stare” phase.
Lifetime
Satellite built and verified for an in-orbit lifetime of 6.5 years and to accommodate consumables for 8 years.
Duty cycle
≥ 93% per target in a year
Launcher
Launch by Soyuz-Fregat2-1b from Kourou in 2026 (compliant with a Ariane 6 launch)
Orbit
Transfer to L2, then large amplitude libration orbit around L2
Description of Spacecraft
Stabilisation
3-axis
Telemetry band
X and K-band
Average downlink capacity
~ 435 Gb per day
Pointing stability
0.2 arcsec (Hz)-1/2 over time scales of 25 s to 14 hours
Pointing strategy
A 90° rotation around the line of sight every 3 months
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