Cheops at ESA's technical centre

The CHaracterising ExOPlanet Satellite, Cheops, in the Rosetta room at ESA's technical centre in the Netherlands in September 2018.

Cheops 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.