SATLASOptical · Space
CHEOPS
CHaracterising ExOPlanet Satellite
OperatingOperating since 18 December 2019.
A 32 cm Ritchey–Chrétien telescope built for ultra-high-precision photometryphotometryMeasuring the flux of a source in a passband. Aperture photometry sums pixels inside a region; PSF photometry fits the point-spread function; forced photometry measures at a position fixed in advance, whether or not a source is detected there. of stars already known to host planets, to 20 ppmppmParts per million of a star's flux; the unit of precision for transit and asteroseismic photometry. in 6 hours on G5 dwarfs of magnitudemagnitudeA logarithmic flux scale, m = −2.5 log₁₀(F/F₀): five magnitudes is a factor of 100, and larger is fainter. The naked eye reaches about 6; single Rubin exposures reach about 24 in r. 6–9. TransittransitA planet passing in front of its star and blocking a fraction (R_p/R_*)² of its light, about 84 ppm for an Earth across the Sun. Repeated transits give period and radius; spectra taken during transit probe the planet's atmosphere. depths precise enough, combined with radial-velocity masses, to measure the bulk densities of super-Earths and sub-Neptunes.
- Operator
- ESA, Switzerland
- Orbit
- Sun-synchronous low Earth orbit
- Aperture
- 32 cm
- Passband
- 330 nm – 1100 nm
- Launch
- 18 December 2019
Passband
Sky coverage
Pointed observationspointed observationObserving chosen targets, usually selected by peer review in annual proposal cycles, as opposed to surveying the sky systematically. Gives depth on few objects; the total area observed stays small. of known planet hosts from a 700 km dawn–dusk Sun-synchronous orbit; Earth occultations and South Atlantic Anomaly passages interrupt most visits.
Archives
Sources
Verified 15 November 2026.