New Mars Moon Ephemerides in the Context of the December 2013 Mars Express Phobos Close Flyby

International audienceAlmost 70 years after its discovery (Sharpless 1945), Phobos tidal acceleration is still the only way to assess Mars tidal dissipation from observations. But monitoring the Phobos' and Deimos' motion has also important consequences for the success of space experiments. In particular, flyby of moons by spacecraft are the opportunity to quantify with great accuracy gravitational field parameters and to constrain their interior. On December 29th 2013, Mars Express (MEX) crossed Phobos' path at a daring distance of less than 50 km. Due to the satellite's small size, an accuracy of 100 meters on Phobos' position is mandatory to allow for a reliable gravity field estimation. To reach this goal, we reduced 340 astrometric observations acquired by the Super Resolution Channel (SRC) camera onboard of MEX during 38 flybys between May 2013 and February 2014. Moreover, efforts have been done to model the Mars moon dynamical environment with unprecedented accuracy. In particular, last results on Mars rotation as well as the introduction for the first time of asteroids perturbations on the motion of the Martian satellites have been considered. Last, improved trajectories of MEX during SRC observation times have been developed