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, observes 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 flys at an altitude of about 700 km and observes roughly 500 bright stars, to characterize their planets. CHEOPS employs 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 provide us with precise densities that tell us about the bulk composition, e.g. whether the planet is dominated by rocks, ice or gas or whether it hosts an atmosphere.

The IWF built one of the two on-board computers, which controls the instrument, manages the science data, and stabilizes the detector temperature. Additionally, the institute participated in the development of the software.

The IWF was involved in the preparation of the CHEOPS mission at science team level (performing observation feasibility modeling, understanding the host star properties and photometric behavior, and CHEOPS observing program definition) and is represented on both the CHEOPS Board and the Science Team (Meet the CHEOPS Team).

The research group Exoplanets: Weather and Climate provides 3D atmosphere models that are used for the interpration of the climate of exoplanets via precise CHEOPS phase curves and secondary eclipse measurements.

The research group Exoplanets: Characterisation and Evolution analyses the CHEOPS data during primary and secondary transit, i.e. when the planet is in front of or behind the star. Furthermore, the masses and ages of the observed stars are calculated and the masses of some planets are determined. By interpreting the CHEOPS data, the development of the planets' atmospheres is explored.

Detailed information can be found at the University of Bern and ESA.

CHEOPS observations-based education activity: "Hack an exoplanet"

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