The Mini Fine Sun Sensor (Mini-FSS) is an analogue sensor, based on the use of a quadrant detector which is capable of measuring the solar aspect angle in two axis. Processing the four quadrant outputs results in the two components and of the solar aspect angle. The applied algorithms cancel out all disturbances that are common to the four quadrants, such as temperature effects, particle radiation degradation, window performance and scale factors. For the conversion to signals that can be used by the spacecraft electronics system, the spacecraft may use passive conversion into signal voltages across load-resistors, or active conversion using current-to-voltage converters.

The Mini-FSS is designed for long duration low earth orbit missions. The Mini-FSS variant without read-out electronics is especially suited for small satellites.