Arianespace has signed a contract with the European Space Agency (ESA) to launch the Characterising Exoplanet Satellite (CHEOPS), which is its upcoming exoplanet mission as part of ESA’s science program.

Arianespace will launch the satellite from the Guiana Space Center, Europe’s spaceport in Kourou, French Guiana, between late 2018 and early 2019 using a Soyuz launch vehicle.

CHEOPS will target nearby, bright stars already known to have planets orbiting around them. Through high-precision monitoring of a star’s brightness, scientists will examine the transit of a planet as it passes briefly across the star’s face. In turn, this will allow an accurate measurement of the planet’s radius. For those planets with a known mass, the density will be revealed, providing an indication of the internal structure.

According to ESA, these key parameters will help scientists to understand the formation of planets from a few times the mass of the Earth (known as “super-Earths”) up to Neptune-sized worlds. The data also will help refine ideas about how planets change orbits during the formation and evolution of their parent systems.

CHEOPS is an ESA mission implemented in partnership with Switzerland and a number of other member states.

Based on an Airbus Defense and Space satellite platform, CHEOPS will weigh about 300 kg. at launch, and will be injected into a 700-km.-altitude sun-synchronous dawn-to-dusk orbit around Earth, inclined by approximately 98 degrees to the Equator as it circles the globe from pole to pole.