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Characterising Exoplanets Satellite
CHEOPS spacecraft
Artist's impression of the CHEOPS spacecraft bus
Operator Swiss Space Office
Mission duration 3.5 yrs (planned)
Spacecraft properties
Bus SEOSAT platform
Manufacturer Airbus Defence and Space
Launch mass ~300 kg (660 lb)
Payload mass 58 kg (128 lb)
Dimensions 1.5 x 1.5 x 1.5 m
Power ~64 watts[1]
Start of mission
Launch date 2019[2][3]
Rocket Soyuz[4]
Launch site Guiana Space Centre
(Ensemble de Lancement Soyouz)
Contractor Arianespace[2]
Orbital parameters
Reference system Geocentric
Regime Sun-synchronous 6 am/pm
Perigee 700 km (430 mi)[3]
Apogee 700 km (430 mi)[3]
RAAN 6am
Type Ritchey-Chretien
frame-transfer back-side illuminated CCD
Diameter 32 cm (13 in)[3]
Focal length F/8
Wavelengths 330-1100 nm

CHEOPS mission logo
ESA astrophysics insignia for CHEOPS

CHEOPS (CHaracterising ExOPlanets Satellite) is a planned European space telescope for the study of the formation of extrasolar planets.

CHEOPS is to be ready to launch in early 2019. The mission aims to bring an optical Ritchey–Chrétien telescope with an aperture of 30 cm, mounted on a standard small satellite platform, into a Sun-synchronous orbit of about 700 km (430 mi) altitude. For the planned mission duration of 3.5 years, CHEOPS is to examine known transiting exoplanets orbiting bright and nearby stars.[5]


Organized as a partnership between the European Space Agency (ESA) and the Swiss Space Office, CHEOPS was selected in October 2012 from among 26 proposals as the first S-class ("small") space mission in ESA's Cosmic Vision programme.[5] ESA is the mission architect and responsible for the spacecraft and launch opportunity procurement. The project is led by the Center for Space and Habitability at the University of Bern, Switzerland, with contributions from other Swiss and European universities. The principal investigator for the science instrument is Willy Benz from the University of Bern. After a competition phase, Airbus Defence and Space in Spain was selected as the spacecraft builder.[4] The mission is cost capped at €50 million.[4]


The main goal of CHEOPS will be to accurately measure the radii of the exoplanets for which ground-based spectroscopic surveys have already provided mass estimates. Knowing both the mass and the size of the exoplanets will allow scientists to determine the planets' density and thus their approximate composition, such as whether they are gaseous or rocky. CHEOPS will be the most efficient instrument to search for shallow transits and to determine accurate radii for known exoplanets in the super-Earth to Neptune mass range (1-6 Earth radius).[4]

CHEOPS will measure photometric signals with a precision limited by stellar photon noise of 150 ppm/min for a 9th magnitude star. This corresponds to the transit of an Earth-sized planet orbiting a star of 0.9 Rsun in 60 days detected with a S/Ntransit >10 (100 ppm transit depth). For example, an Earth-size transit toward a G star creates an 80 ppm depth.

The spacecraft is to be powered by solar panels that are also part of its sunshield. They will provide 60 W continuous power for instrument operations and allow for at least a 1.2 gigabit/day data downlink capacity.[6]

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