Mars' time variable gravity: How to improve the solution of its seasonal variations from orbit reconstruction of spacecraft?

Pascal Rosenblatt, Royal Observatory of Belgium, Brussels, Belgium, Jean-charles Marty, GET-CNES, OMP, Toulouse, France, Stefano Bertone, NASA GSFC / UMBC CRESST, Greenbelt, MD, United States, Daniel Arnold, University of Bern, Astronomical Institute, Bern, Switzerland and Adrian Jaeggi, Astronomical Institute, University of Bern, Bern, Switzerland