OSIRIS-REx Pointing Performance

Navigation for spacecraft missions around small bodies requires Optical Navigation (OpNav) to achieve the Orbit Determination (OD) performance necessary to maintain spacecraft safety and achieve mission science objectives. Precise and accurate inertial pointing knowledge in inertial space of the OpNav imager is required to meet this necessary performance. This paper presents results of the OSIRIS-REx OpNav team’s routine trending of the NavCam1 imager pointing with respect to the spacecraft attitude, including analysis of thermal deviations the NavCam boresight correlated with sun-on-deck geometry as well as operation of high-energy instrument payloads. These analyses facilitated the calibration of the imager alignment with respect to the spacecraft and characterized the uncertainties for OpNav pointing. This paper also presents methods and results for a comparison of alternative pointing estimation techniques in order to understand their quality relative to highly accurate star-based pointing solutions. This analysis includes two cases of pointing estimation by the SPC software with different a priori errors and uncertainties, and a third pointing estimate was performed using the OD filter. This analysis characterized the accuracy and precision of these pointing estimation techniques relative to pointing solutions using long-exposure star images. We found that the OD-based pointing solutions performed best when compared to periods where we also had reliable star-based estimates.