Station-Keeping Approach for Extremely Low Lunar Orbits with Solar Sailing

Renewed interest in cislunar space has created opportunities for sustained operations in extremely low-lunar orbits (eLLOs), where altitudes below 50 km enable close surface proximity. However, these orbits are strongly perturbed by the irregular lunar gravity field, leading to rapid eccentricity growth, high station-keeping costs, or even surface impact. Recent advances in our understanding of the lunar “translation theorem” have revealed predictable behavior in the eccentricity vector, offering new opportunities for efficient control. This paper introduces a two-stage framework for solar sail station-keeping in eLLOs. First, a mixed-integer second-order cone programming approach leverages the translational behavior of the eccentricity vector to identify orbit and sail configurations favorable for station-keeping. Second, a lightweight sequential convex programming formulation refines these into high-fidelity trajectories, enabled by a recently developed lossless convexification of solar sail dynamics. A case study inspired by the Lunar Reconnaissance Orbiter mission demonstrates that a realistic solar sail spacecraft can be maintained within the eLLO regime for at least 1 year without propellant expenditure. The approach remains effective at reduced control update frequencies (down to monthly) and exhibits low sensitivity to uncertainties. This study provides evidence that stable station-keeping across the annual variations in sun–moon geometry is possible and therefore indicates the possibility of indefinite station-keeping.