|Operator||Swiss Space Office
|Mission duration||3.5 yrs (planned)|
|Payload mass||58 kg (128 lb)|
|Start of mission|
|Launch date||December 2017 (planned)|
|Rocket||Soyuz or Vega|
|Launch site||Guiana Space Centre|
|Regime||Sun-synchronous 6 am/pm|
|Perigee||650 km (400 mi)|
|Apogee||800 km (500 mi)|
frame-transfer back-side illuminated CCD
|Diameter||32 cm (13 in)|
Foreseen to be launch-ready by the end of 2017, 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 800 kilometres (500 mi) altitude. For the planned mission duration of 3.5 years, CHEOPS is to examine known transiting exoplanets orbiting bright and nearby stars.
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.  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. The mission is cost capped at €50 million.
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' 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).
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.
- CHEOPS exoplanet mission meets key milestones en route to 2017 launch. ESA, 11 July 2014
- CHEOPS - Mission Status & Summary
- "ESA Science Programme's new small satellite will study super-Earths". ESA press release. 19 October 2012. Retrieved 19 October 2012.
- CHEOPS - Requirements
- CHEOPS homepage
- Europe to begin search for habitable planets in our cosmic backyard, 22 October 2012, Stuart Clark, The Guardian
- CHEOPS mission visualization - video
- Video (86:49) - "Search for Life in the Universe" - NASA (July 14, 2014).