Addressing Inaccurate Phase Center Offsets in Precise Orbit Determination for Agile Satellite Missions

Incorrect offsets between a satellite’s center of mass and its global navigation satellite system antenna phase center pose challenges to the precise orbit determination (POD) of many current Earth observation missions. Based on hardware-in-the-loop simulations, this paper demonstrates the more adverse effects on agile satellites, which perform frequent attitude maneuvers around all spacecraft axes. However, findings obtained from an observability analysis and Monte Carlo simulations indicate that rapid attitude changes enable the direct estimation of otherwise unobservable offsets. Application to the POD of agile satellites leads to a consistent and significant performance improvement in the presence of incorrect phase center offsets. Directly estimated corrections for the phase center offset of Sentinel-6A, which performs slews on several occasions, are consistent with values obtained from other studies via independent methods. These results underscore the possibility of estimating the lever arm for both agile and non-agile satellites in dedicated calibration maneuvers.