The Coarse Sun Sensor (CSS) delivers coarse information about the position of the sun relative to the spacecraft. This information is used for coarse maneuvering of the spacecraft and to inform the spacecraft about the position of the sun when it is in a safe mode of operation.

The CSS is a rugged, highly reliable, self-redundant device designed to detect sunlight in potentially a hemispherical field of view (FOV). The sensor is designed to deliver individual detector outputs to the Attitude & Orbit Control Subsystem (AOCS). This approach enables the AOCS to derive solar aspect angles for offset sun positions in a portion of the near-hemispherical FOV of the sun sensor.