Sun Sensor for Absolute Orientation Determination

With an increasing interest in extraterrestrial exploration new systems need to be developed for absolute heading determination, since e.g. the Moon or Mars lack usable magnetic field. This makes the magnetic compass, the most widely used option on Earth, ineffective. We present a novel design for a Sun sensor for absolute heading determination in this paper. It combines three low-cost commercial off-the-shelf 2D analog light angle sensors, each with a 90° field of view, to a single Sun sensor with almost 180° field of view, that can continuously determine the absolute heading at a rate of 200 Hz. The whole system comes in a small size of 9 cm x 9 cm x 4.5 cm and only weighs 45 g. To determine the heading the measurements from all three sensors are combined and compared to the predicted Sun position. A sensitivity analysis is conducted on all inputs for the computation. In our tests a root-mean-square error of 10.7° could be achieved compared to a magnetometer in clear sky conditions.