CHEOPS

CHaracterising ExOPlanets Satellite

Mission Profile

CHEOPS (CHaracterising ExOPlanets Satellite) is ESA's first small-class science mission, launched on 18 December 2019 to a sun-synchronous orbit to precisely measure the sizes of known exoplanets by observing their transits across their host stars with photometric precision exceeding ground-based observatories. Unlike planet-hunting missions that discover exoplanets, CHEOPS targets planets already known from radial velocity surveys, determining their radii to calculate bulk density when combined with known masses — revealing whether a planet is rocky, water-rich, or gas-dominated. The mission has characterized hundreds of exoplanet systems including several multi-planet systems and provided detailed atmospheric characterization targets for the James Webb Space Telescope. CHEOPS operates as a flexible observatory, allocating observing time across European research teams for a broad range of planetary science programs.