Relativistic Warning to Space Missions Aimed to Reach Phobos

Abstract

Disagreement in estimations of the observed acceleration of Phobos yields several theories empirically modifying classical description of motion of the satellite, but its orbital positions detected by Mars-aimed spacecraft differ from predictions. It is shown that the satellite's orbital perturbations can be explained as manifestations of the relativistic time-delay effect ignored in classical models. So computed limits of Phobos' acceleration essentially exceed the experimental values. The satellite's expected orbital shift is calculated for the moment of contact with a landing module of the Phobos-Grunt project; the shift assessed in kilometers may prevent the mission success. Limits of the apparent relativistic accelerations are predicted for fast satellites of Jupiter.