Solar system expansion and strong equivalence principle as seen by the NASA MESSENGER mission

The NASA MESSENGER mission explored the innermost planet of the solar system and obtained a rich data set of range measurements for the determination of Mercury's ephemeris. Here we use these precise data collected over 7 years to estimate parameters related to general relativity and the evolution of the Sun. These results confirm the validity of the strong equivalence principle with a significantly refined uncertainty of the Nordtvedt parameter eta = (-6.6 +/- 7.2) x 10(-5). By assuming a metric theory of gravitation, we retrieved the post- Newtonian parameter beta = 1 + (-1.6 +/- 1.8) x 10(-5) and the Sun's gravitational oblateness, J(2 circle dot) = (2.246 +/- 0.022) x 10(-7). Finally, we obtain an estimate of the time variation of the Sun gravitational parameter, GM(circle dot)/GM(circle dot) = (- 6.13 +/- 1.47) x 10(-14), which is consistent with the expected solar mass loss due to the solar wind and interior processes. This measurement allows us to constrain vertical bar(D)over dot vertical bar/G to be <4 x 10(-14) per year.