Solar Sails and Lunar South Pole Coverage

Abstract

Potential orbits for continuous surveillance of the lunar south pole with just one spacecraft and a solar sail are investigated. Periodic orbits are first computed in the EarthMoon Restricted Three-Body Problem, using Hermite-Simpson and seventh-degree GaussLobatto collocation schemes. The schemes are easily adapted to include path constraints favorable for lunar south pole coverage. The methods are robust, generating a control history and a nearby solution with little information required for an initial guess. Five solutions of interest are identified and, using collocation, transitioned to the full ephemeris model (including the actual Sun-to-spacecraft line and lunar librations). Of the options investigated, orbits near the Earth-Moon L2 point yield the best coverage results. Propellant-free transfers from a geosynchronous transfer orbit to the coverage orbits are also computed. A steering law is discussed and refined by the collocation methods. The study indicates that solar sails remain a feasible option for constant lunar south pole coverage.