Design of long-lifetime lunar orbits: A hybrid approach

Abstract The behavior of low altitude near-circular lunar orbits is a key design issue for some missions related to the physical exploration of the Moon. Because of its masconian character, the gravity field of the Moon requires higher order truncations to give a realistic description of the long-term behavior of low-lunar orbits. We show that the required understanding of the dynamical behavior in the vicinity of the Moon can be reached through the combination of analytical techniques and periodic orbits computation. A model that consists of a high degree, zonal truncation of the Selenopotential superimposed to the Earth mass-point attraction is used to explore the existence and orbital characteristics of long-lifetime orbits close to the Moon at any inclination. The averaging provides a global view on the frozen orbit's geometry and local descriptions of the averaged flow. But it also makes available the short-period terms of the transformation from mean to osculating elements. A refinement of the osculating elements by means of differential corrections allows to compute lunar repeat ground-trace orbits in high fidelity potentials without restricting to zonal models.