Use of MESSENGER radioscience data to improve planetary ephemeris and to test general relativity

TL;DR

This paper utilizes MESSENGER radioscience data to significantly enhance Mercury's orbital models and planetary ephemerides, enabling more precise tests of general relativity and PPN parameters.

Contribution

It introduces an improved planetary ephemeris, INPOP13a, derived from MESSENGER data, and provides more stringent constraints on PPN parameters for gravity theories.

Findings

Enhanced accuracy of Mercury's orbit from MESSENGER data

Improved planetary ephemeris INPOP13a

More stringent tests of general relativity

Abstract

The current knowledge of Mercury orbit has mainly been gained by direct radar ranging obtained from the 60s to 1998 and by five Mercury flybys made by Mariner 10 in the 70s, and MESSENGER made in 2008 and 2009. On March 18, 2011, MESSENGER became the first spacecraft to orbit Mercury. The radioscience observations acquired during the orbital phase of MESSENGER drastically improved our knowledge of the orbit of Mercury. An accurate MESSENGER orbit is obtained by fitting one-and-half years of tracking data using GINS orbit determination software. The systematic error in the Earth-Mercury geometric positions, also called range bias, obtained from GINS are then used to fit the INPOP dynamical modeling of the planet motions. An improved ephemeris of the planets is then obtained, INPOP13a, and used to perform general relativity tests of PPN-formalism. Our estimations of PPN parameters (beta and gamma?) are more stringent than previous results.