Stability of Highly Elliptical Orbits at the Moon

In this paper, we present the results of an investigation into the dynamics of a special class of science orbits at the Moon, characterized by high apoapsis and low periapsis altitudes: highly elliptical orbits. The combination of relatively high apoapsis and low periapsis altitudes results in complex stability characteristics. We assess the natural evolution of these orbits and the station-keeping V necessary to maintain them within dened constraints, over the period of one year. We outline the strong dependence of orbital stability on inclination, right ascension of the ascending node, and argument of periapsis. Further, we identify orbits that mimic the behavior of frozen orbits and are potential candidates for further research to minimize station-keeping requirements. Finally, we also provide results from an initial study performed to assess the station-keeping requirements. We see that the station-keeping V necessary to maintain these orbits is strongly a function of the initial orbital parameters chosen. In the most optimal cases the V can be less than 100m/s; however, in particularly bad cases it can exceed 1000m/s. Hence, the choice of initial orbital parameters is crucial to mission success.