# CHEOPS
Who / What
CHEOPS (CHaracterising ExOPlanets Satellite) is a European space telescope designed to study the sizes of known extrasolar planets. By measuring precise changes in brightness as these planets pass in front of their host stars, it enables scientists to estimate their masses, densities, compositions, and formation processes.
Background & History
CHEOPS was developed under the framework of ESA’s (European Space Agency) Cosmic Vision scientific program, specifically as a Small-class mission. It was selected for launch following an open call for proposals in 2012. The satellite was built by a consortium led by Switzerland, with contributions from several European countries and international partners. After years of development, CHEOPS was launched on **18 December 2019** aboard a Soyuz rocket from the Guiana Space Centre in French Guiana.
Why Notable
CHEOPS represents a groundbreaking advancement in exoplanet research by providing high-precision measurements of planetary radii. Its data complements observations from other missions like Kepler and TESS, offering critical insights into the nature of transiting exoplanets—particularly those already known to have masses determined through radial velocity methods. By refining our understanding of planet compositions (e.g., rocky vs. gaseous), it contributes directly to broader astrophysical questions about planetary formation and habitability.
In the News
Since its launch, CHEOPS has delivered groundbreaking results, including the discovery of a super-Earth with an unusually high density and the characterization of planets in close orbits around bright stars. Its ongoing observations continue to refine models of exoplanet evolution, making it a key player in the search for Earth-like worlds. The mission’s success has also spurred interest in future missions focused on atmospheric studies and direct imaging of exoplanets.