The Development of an Attitude Sensing System for Small Satellites

This paper describes the attitude sensing system developed by Globesat, Inc. for its gravity-gradient-stabilized satellites. Compactness, low cost, low power, and high performance were the main considerations of the system design. The sensor is based on a commercial CCD video camera for imaging the sun and the horizon. The images are digitized by a frame grabber and then processed for attitude computation. The system has a field of view of 90 X 360 and can determine attitude to 10 or better. Using the sun and nadir vectors as references, the orientation of the satellite with respect to the Earth is completely determined. The method used for the attitude calculations is outlined in this paper