Abstract
AbstractOrbit determination of probes visiting Solar System bodies is currently the main source of our knowledge about their internal structure, inferred from the estimate of their gravity field and rotational state. Nongravitational forces acting on the spacecraft need to be accurately included in the dynamical modeling (either explicitly or in the form of empirical parameters) not to degrade the solution and its geophysical interpretation. In this study, we present our recovery of NASA GRAIL orbits and our lunar gravity field solutions up to degree and order 350. We propose a systematic approach to select an optimal parametrization with empirical accelerations and pseudo‐stochastic pulses, by checking their impact against orbit overlaps or, in the case of GRAIL, the very precise inter‐satellite link. We discuss how parametrization choices may differ depending on whether the goal is limited to orbit reconstruction or if it also includes the solution of gravity field coefficients. We validate our setup for planetary geodesy by iterating extended lunar gravity field solutions from pre‐GRAIL gravity fields, and we discuss the impact of empirical parametrization on the interpretation of gravity solutions and of their error bars.
Highlights
Navigation of deep space probes is currently mainly based on Doppler tracking by Earth based antennas
We validate our setup for planetary geodesy by iterating extended lunar gravity field solutions from pre-GRAIL gravity fields, and we discuss the impact of empirical parametrization on the interpretation of gravity solutions and of their error bars
6 Conclusions At Astronomical Institute of the University of Bern (AIUB), orbit determination capabilities from Doppler deep-space tracking have been recently developed in the framework of the Bernese GNSS Software following the guidelines of Moyer (2003) and the most recent conventions for planetary reference frames and ephemerides
Summary
Navigation of deep space probes is currently mainly based on Doppler tracking by Earth based antennas. We present the planetary extension within the development version of the Bernese GNSS Software (BSW, Dach et al, 2015) We use it to provide independent solutions for the orbits of GRAIL-A and GRAIL-B and for the gravity field of the Moon up to degree and order (d/o) 350 in spherical harmonic expansion based on data from the GRAIL Primary Mission (PM, 01-Mar-2012 to 29-Apr-2012). These are in turn used to setup the observation equations required for the least-squares recovery of arc-specific orbital and global (e.g., gravity field coefficients) parameters. The orbits emerging from this procedure serve as a priori orbits for the setup of the generalized OD and the solution of NEQs containing both orbit and gravity field parameters
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