The Cosine Sun Sensor Redundant (CoSS-R) delivers coarse information about the position of the sun relative to the spacecraft with integrated redundancy. This information is used for coarse maneuvering of the spacecraft and to inform the spacecraft about the position of the sun.

With a suite of CoSS-R, of which at least three sensors with different viewing directions have the sun in their field of view, the Attitude & Orbit Control Subsystem (AOCS) can retrieve the position of the sun in the coordinate reference system of the spacecraft.

The design of the CoSS-R exploits the excellent heritage of the dual chip detectors while optimizing the footprint and mass. The core element is the detector which is based on proven technology applied in the Coarse Sun Sensor (CSS) formerly known as Sun Acquisition Sensors (SAS) with an excellent heritage since 1975.