NSS Fine Sun Sensor
The sun sensor determines the spacecraft body angles with respect to the sun. It accepts configuration commands and outputs digital angles and telemetry over a serial interface to the on-board computer. The unit is powered from unregulated DC power from the spacecraft.
The front surface of the sensor is a mirror with slits cut in the reflective metal. Sunlights passes through these slits and then through an optical filter. Below this is an array of photosensors interfaced to a micro-controller.
The charge on the photosensors are read by the micro-controller, which processes the image and computes the sun vector. The vector and other telemetry is returned to the spacecraft through the serial interface.