The CHaracterising ExOPlanet Satellite (CHEOPS) is an S-class ESA satellite mission dedicated to the study of extrasolar planets. CHEOPS, successfully launched on 18 Devember 2019, will observe planetary systems at an unprecedented photometric precision.
The main science goals of CHEOPS are to find transits of small planets, known to exist from radial-velocity surveys, measure precise radii for a large sample of planets to study the nature of Neptune- to Earth-sized planets, and obtain precise observations of transiting giant planets to study their atmospheric properties.
CHEOPS was built by an international consortium under the leadership of Willy Benz, Universiy of Bern, and ESA. CHEOPS weights about 200 kg and carries a 30 cm telescope. The satellite will fly at an altitude of about 700 km and it will observe roughly 500 bright stars, to characterize their planets, within three and a half years. CHEOPS will employ the transit method to precisely measure the size of planets, through the measurement of the dimming of light caused by the obscuration of part of the stellar disk by the planet. Together with previous radial velocity measurements, which deliver planetary masses, CHEOPS will provide us with precise densities that will tell us about the bulk composition, e.g. whether the planet is dominated by rocks, ice or gas or whether it hosts an atmosphere.
IWF has built one of the two on-board computers, which controls the instrument, manages the science data, and stabilizes the detector temperature. The Exoplanets group was involved in the preparation of the CHEOPS mission at the science team level (performing observation feasibility modeling, understanding the host star properties and photometric behavior, and CHEOPS observing program definition). Furthermore, IWF is member of the CHEOPS Board.