Autonomous Station Keeping of Satellites in Areostationary Mars Orbit: A Predictive Control Approach

TL;DR

The paper tackles autonomous station keeping for an areostationary Mars orbiter by formulating a nonlinear model predictive control policy that directly minimizes annual Δv under a high-fidelity environment model. It demonstrates that leveraging non-Keplerian perturbations and optimizing horizon and drift-window parameters yields substantial fuel savings across longitudes, including a practical case over Southern Meridiani Planum and an alternative stable-longitude design. Key contributions include a detailed environmental model (gravity harmonics, SRP, celestial perturbations), an implementable nMPC framework, and systematic longitudes/epoch analyses that guide mission-design decisions. The findings support fuel-efficient AMO station keeping and offer design insights for future Mars relay networks and ground-to-space communication infrastructures.

Abstract

The continued exploration of Mars will require a greater number of in-space assets to aid interplanetary communications. Future missions to the surface of Mars may be augmented with stationary satellites that remain overhead at all times as a means of sending data back to Earth from fixed antennae on the surface. These areostationary satellites will experience several important disturbances that push and pull the spacecraft off of its desired orbit. Thus, a station-keeping control strategy must be put into place to ensure the satellite remains overhead while minimizing the fuel required to elongate mission lifetime. This paper develops a model predictive control policy for areostationary station keeping that exploits knowledge of non-Keplerian perturbations in order to minimize the required annual station-keeping $Δv$. The station-keeping policy is applied to a satellite placed at various longitudes, and simulations are performed for an example mission at a longitude of a potential future crewed landing site. Through careful tuning of the controller constraints, and proper placement of the satellite at stable longitudes, the annual station-keeping $Δv$ can be reduced relative to a naive mission design.

Figures (13)

• Figure 1: Illustration of the MCI frame (aligned with $\mathcal{F}_a$) and Hill's frame ($\mathcal{F}_h$) attached to the spacecraft (point $c$) in a circular equatorial areostationary orbit. This figure also shows the spacecraft drift, $\delta {\underrightarrow{{r}}}$, relative to the station-keeping window fixed in Hill's frame and centered at point $h$. Stationary orbit and planet sizes are not to scale.
• Figure 2: A time history of disturbance acceleration components (m/s$^2$) in Hill's Frame $\mathcal{F}_h$ at a stable longitude ($17.92^\circ$ W) and an unstable longitude ($148^\circ$ W) over 668.6 orbits, which is 687 Earth days, the length of Mars' orbital period around the sun.
• Figure 3: Plots of uncontrolled error in latitude-longitude position relative to stationary orbit at (a) unstable ($148^\circ$ W) and (b) stable ($17.92^\circ$ W) longitudes over 100 orbits.
• Figure 4: Satellite response to a naïve station-keeping policy where along-track and cross-track perturbations are canceled out leaving only radial perturbations. Image shows satellite radial position and longitude (blue) vs number of orbits, and longitudinal bounds of an imaginary station-keeping window at $\pm 0.05^\circ$ (red) and $\pm 0.25^\circ$ (black).
• Figure 5: Annual (355-orbit) $\Delta v$ required for areostationary station keeping across all longitudes. The results in black ($\lambda$-drift only) use the station-keeping policy in Ref. Silva2013. The results in blue (complete station keeping) use the nonlinear MPC policy introduced in Section \ref{['sec:MPC']}.