Abstract. A method is proposed for generating refined estimates of the position angles of star sensors rigidly fixed on the spacecraft body, in the presence of high-precision data on the orbit parameters. The instrumental errors in measuring stars coordinates by the sensors are several tenths of a second of arc. The estimates of the position angles of the trackers optical axes are determined by numerically solving a system of matrix equations. Application of the propose method leads to a significant, by one or two orders of magnitude, reduction in the errors in the orientation parameters of the instruments relative to the spacecraft body and, as a result, to formation of high-precision estimates of the spacecraft body orientation parameters in the geocentric and moving orbital coordinate systems. The resulting average errors do not exceed a few arcseconds, and sometimes decrease to the level of instrumental errors in measuring the coordinates of stars by the trackers. Results of modeling are presented and recommendations for the algorithm application are given.

Keywords: autonomous orientation, autonomous navigation, onboard control system, spacecraft, star tracker, random measurement errors

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