Recomputation and Updating of MOLA Geolocation

Abstract

The Mars Orbiter Laser Altimeter (MOLA) Precision Experiment Data Records (PEDR) serve as the geodetic reference of Mars. However, these MOLA footprints were geolocated using outdated auxiliary information that dates back to 2003. In this study, we recompute the MOLA PEDR footprint locations and investigate the impact of the updated spacecraft orbit model and Mars rotational model on MOLA’s geolocation. We observe quasi-exponential increases near the poles of up to 30 m in the recomputation residuals for the nadir profiles. Meanwhile, we demonstrate that limitations exist in the stored MOLA PEDR attitude records, which can shift the footprint up to hundreds of meters laterally and several meters radially. The usage of the Navigation and Ancillary Information Facility (NAIF)-archived attitude information instead can circumvent this issue and avoid the approximation errors due to discrete samplings of the attitude information used in geolocation by the PEDR dataset. These approximation errors can be up to 60 m laterally and 1 m radially amid controlled spacecraft maneuvers. Furthermore, the incorporation of the updated spacecraft orbit and Mars rotational model can shift the MOLA profiles up to 200 m laterally and 0.5 m radially, which are much larger in magnitude than the aforementioned dramatic increases near the poles. However, the shifted locations of the reprocessed profiles are significantly inconsistent with the PEDR profiles after the global cross-over analysis.