The Pyramid Star Identification Technique

ABSTRACT: A new highly robust algorithm, called Pyramid, is presented to identify the stars observed by star trackers in the general lost-in-space case, where no a priori estimate of pointing is available. At the heart of the method is the k-vector approach for accessing the star catalog, which provides a searchless means to obtain all cataloged stars from the whole sky that could possibly correspond to a particular measured pair, given the measured interstar angle and the measurement precision. The Pyramid logic is built on the identification of a four-star polygon structure—the Pyramid—which is associated with an almost certain star identification. Consequently, the Pyramid algorithm is capable of identifying and discarding even a high number of spikes (false stars). The method, which has already been tested in space, is demonstrated to be highly efficient, extremely robust, and fast. All of these features are supported by simulations and by a few ground test experimental results.