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 Star Sensor (MOSS) mounted on a spacecraft. In particular, the coordinates 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 complexity 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 dedicated hardware, can locate a star configuration in less than 1 s. Errors in the position and magnitude of each star, due to sensor tolerances, are taken into account and the configuration is detected regardless of its orientation. The search is performed over the whole celestial sphere. Ambiguous matchings (i.e. other configurations compatible with the stars detected by the sensor) are taken into account. The error probability of the algorithm is also investigated.