Harmony, ESA's 10th Earth Explorer mission, consists of 2 satellites that will orbit Earth in tandem with a Copernicus Sentinel-1 satellite in various configurations. The Harmony satellites’ synthetic aperture radar instruments will receive the Sentinel-1 satellite's radar signals that bounce back, or ‘backscatter’, from Earth’s surface. At the same time, Harmony’s thermal-infrared instruments provide complementary observations of the sea surface as well as the position and motion of clouds above it.