Cheops, the Characterising Exoplanet Satellite, is ESA’s first mission dedicated to the study of extrasolar planets, or exoplanets. It will observe bright stars that are already known to host planets, measuring minuscule brightness changes due to the planet’s transit across the star’s disc.
The design of Cheops was driven by the need to precisely measure the ‘signal’ from exoplanet host stars. Precision is of particular importance because the transit signal can be extremely tiny for the smallest planets, and noise from the instrument itself can potentially obscure the transit. The instrument therefore needs to be as stable as possible, both in terms of keeping jitter to a minimum while observing the star in ‘stare and track’ mode, and in keeping cool to avoid thermally-induced noise.