Updated Mars Gravity Field with Five Additional Years of Lower-Noise MRO Doppler Tracking

Abstract:

The Mars gravity field has been globally mapped over more than two decades by polar orbiters, particularly the NASA Mars Global Surveyor (MGS; 1999-2006), Mars Odyssey (ODY; 2002-present), and Mars Reconnaissance Orbiter (MRO; 2006-present) spacecraft. While each brought appreciable improvement to the determination of the global gravity field spherical harmonics coefficients from their new orbit geometry, particularly lower altitude like MRO, their primary orbital characteristics have not changed. The buildup of the data coverage has been beneficial to extending the global effective spatial resolution of the field (to ~115km) and monitoring the seasonal atmosphere-cap mass exchanges.

Here, we analyze the recent MRO tracking data that were not included in the Genova et al. (2016, Icarus) study. Although they follow almost ten years of prior MRO tracking, these additional five years of data are still promising because the Doppler noise level was substantially reduced in March 2014, when the backup transponder alleviated a spurious 0.2-0.3 Hz noise signature. In effect, our new solutions complement the one year of higher-quality MRO dataset of Genova et al. (2016) with five more years. We will present an updated global gravity field model, measure its performance, for instance in terms of spatial resolution, and discuss the geophysical implications.