Revised Ephemerides of the Martian Satellites, Phobos and Deimos

We report on the new ephemerides (MAR099) for the satellites of Mars derived from 7 a large set of ground-based and spacecraft astrometric measurements. Our integrated 8 orbit fit yielded latest estimates for the Martian tidal parameter τ = k2/Q = 1.816 ± 0.084×10−3 and half the tidal acceleration of Phobos of s = 1 2 n˙ = 1.258±0.058×10−3 9 deg yr−2 10 . We used the spacecraft-measured physical libration amplitude of Phobos, 11 A = 1.14 ± 0.03 deg, to fit J2 and C22 and found that the result is consistent with 12 the value derived from its shape and the uniform density assumption. The data show 13 no sensitivity for the physical libration of Deimos. We report on the statistics of the 14 observation residuals, the satellites’ orbital elements, and projected uncertainties of 15 the satellites’ positions in the next few decades.