Cheops will be a secondary passenger on a Soyuz-Fregat rocket launching from Europe’s Spaceport in Kourou, French Guiana. Launch is foreseen in mid-December 2019.
The launcher will deliver Cheops directly to its operational orbit, a Sun-synchronous dusk–dawn orbit 700 km above Earth.
This orbit allows the rear of the craft to permanently face the Sun with a minimum number of eclipses, offering a stable thermal environment and keeping stray light to a minimum while the instrument is observing night-side targets in the direction opposite to the Sun.
During each orbit the satellite will slowly rotate around the telescope line of sight to keep the instrument radiators orientated away from Earth and therefore maintain the required detector temperature stability needed for precise measurements.