A NEW STAR-CONSTELLATION MATCHING ALGORITHM FOR SATELLITE ATTITUDE DETERMINATION

An important task in spacecraft control is the computation of attitude information. An algorithm is described here which allows the recovery of position information by processing data obtained from a Modular St ar Sensor (MOSS) mounted on a spacecraft. In particular, the coordinat es of the region of space in the sensor field of view are obtained by matching the star configuration detected by the MOSS with those in the ESA Stellar Catalogue. Great attention has been given to the complexi ty of the algorithm, which must deal with an extremely large volume of data, due to the large number of stars in the Catalogue. Experimental results indicate that the system, if implemented by means of dedicate d hardware, can locate a star configuration in less than 1 s. Errors i n the position and magnitude of each star, due to sensor tolerances, a re taken into account and the configuration is detected regardless of its orientation. The search is performed over the whole celestial sphe re. Ambiguous matchings (i.e. other configurations compatible with the stars detected by the sensor) are taken into account. The error proba bility of the algorithm is also investigated.