  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.
