SPACECRAFT METHODS AND SYSTEMS FOR AUTONOMOUS CORRECTION OF STAR TRACKER CHARGE-TRANSFER-EFFICIENCY ERRORS

摘要

Structures and methods are provided for deriving corrected star coordinates C_crctd from measured star coordinates C_ms that include star tracker charge transfer efficiency (CTE) errors. The structures and methods are based on a recognition that measured star coordinates C_ms of star image centroids include CTE errors which are functions of the CCD path lengths over which the associated electrical charges traveled. In particular, the errors are substantially a product of a respective path length and a star-coordinate error factor which, in turn, is a function of the star image magnitudes m_si. Information contained in different measured star coordinates C_ms is organized to facilitate the derivation of an estimate * of the star-coordinate error factor with conventional estimation processes. The measured star coordinates C_ms are then corrected with the error factor estimate * to realize the corrected star coordinates C_crctd and, thereby, improve the accuracy of spacecraft attitude control.