Predictive Station Keeping of Areostationary Satellites Using Natural Motion Trajectories

Future expeditions to the Martian surface will require satellite presence to enable navigation and communication. Satellites in areostationary orbit around Mars will make up an important aspect of a potential constellation since they remain stationary relative to a ground observer, providing a means to transfer data to and off the planet with a fixed antenna. Forces experienced by such a satellite will cause it to drift from its nominal orbit, which needs to be mitigated by station keeping. The unique challenges associated with Mars’ gravitational field and the large communication delay between Earth and Mars motivates the need for novel, autonomous station-keeping policies for areostationary satellites that leverage highly efficient, low-thrust electric propulsion. In this paper, we introduce an approximation of the dynamical equations of motion compatible with on-line execution of a predictive control policy. Specifically, this novel formulation allows predictive station-keeping policies to harness gravitational perturbations to maintain a natural motion trajectory in orbit around Mars to reduce fuel consumption without compromising on-line computation complexity. The novel contributions of this work include: An autonomous station keeping policy that reduces fuel consumption by following natural limit cycles caused by phenomena in the Martian gravitational potential present at certain longitudes. A general framework for off-line computation of accurate linear models that would be used during operation.