Nobel laureate Michel Mayor (left) and ESA Cheops project scientist Kate Isaak (right) during a Cheops media briefing at the joint meeting of the European Planetary Science Congress and the Division for Planetary Sciences of the American Astronomical Society EPSC-DPS held in September 2019 in Geneva, Switzerland.
Cheops, the CHaracterising ExOPlanet Satellite, is ESA's first mission dedicated to the study of exoplanet. Scheduled for launch in mid December 2019, it will make observations of exoplanet-hosting stars to measure small changes in their brightness due to the transit of a planet across the star's disc, targeting in particular stars hosting planets in the Earth-to-Neptune size range. The information will enable precise measurements of the sizes of the orbiting planets to be made: combined with measurements of the planet masses, this will provide an estimate of their mean density – a first step to characterising planets outside our Solar System.
Cheops is the first small, or S-class, mission in ESA's science programme. It is a partnership between ESA and Switzerland, with a dedicated Consortium led by the University of Bern, and with important contributions from 10 other ESA Member States.