CHEOPS

Rather than searching for new planets, CHEOPS (Characterising Exoplanets Satellite) targets those already found. It records the precise dip in stellar brightness as a known exoplanet crosses its host star - from which the planet's radius can be derived; combined with ground-based mass estimates, those radii yield bulk densities and likely compositions for worlds ranging from super-Earths to Neptunes.

ESA's first S-class mission under the Cosmic Vision programme, CHEOPS was selected in October 2012 from 26 competing proposals.