The CHaracterising ExOPlanet Satellite, CHEOPS, in the clean room at Airbus Defence and Space Spain, Madrid, in February 2019. The satellite was declared ready to fly and will target the period between 15 October and 14 November for launch. 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.
Cheops paves the way for the next generation of ESA's exoplanet satellites, with two further missions – PLATO and ARIEL – planned for the next decade to tackle different aspects of the evolving field of exoplanet science.