Sensor data simulations for a future dedicated satellite gravimetry mission at Mars

Improving the data on the gravitational field of Mars enhances our knowledge about Martian planetary dynamics and subsurface water reservoirs. A future dedicated satellite gravimetry mission at Mars following the archetype of GRACE-FO, with two identical spacecraft chasing one-another along a low polar orbit, has been proposed. Measuring changes in their mutual separation could produce valuable data for the derivation of improved static and time variable gravity field solutions of Mars.

Requirement for such a mission are primarily two sensors: an accelerometer located at the center of mass of the spacecrafts and a ranging measurement system. The latter one is used to measure the range variations e.g. via laser interferometry, as the separation between both spacecrafts varies due to gravity anomalies. The accelerometer is needed to distinguish between gravitational accelerations and non-gravitational perturbations acting on the satellite.

Compared to terrestrial missions, the Martian environment implies several challenges. Using doppler tracking instead of a GNSS system reduces positioning accuracy. Insufficiently known data on Mars Orientation Parameters may result in misinterpretations within the gravity field recovery process. Existing models for atmospheric drag fail to describe short term variations in the Martian upper atmosphere. The accelerometer is mitigating this by measuring the non-gravitational accelerations acting on the spacecraft.

Simulating the output of both sensors is valuable to evaluate the sensor requirements needed to ensure the quality of the scientific outcome of the mission. It enables to decide upon technical and mission details such as orbital parameters and to assess the feasibility of such a mission in general. For this purpose, we develop a simulation tool for the precise orbit propagation. It includes the modelling of gravitational and non-gravitational forces for orbit integration. Together with a sensor model for both the accelerometer and a laser ranging interferometer, it can emulate realistic sensor outputs. In this talk, we present the first version of simulated sensor data.