Generation of Optimal Forced Periodic Trajectories: Lunar Pole-Sitting Orbits

In Cislunar space, spacecraft are able to exploit naturally periodic orbits, which provide operational reliability. However, these periodic orbits only exist in a limited volume. We show that spacecraft equipped with low-thrust propulsion can follow a greater number of periodic trajectories in Cislunar space. Among these trajectories are pole-sitters, or trajectories that orbit North or South of the Moon throughout the whole orbit. Pole-sitters may be used to complement future Lunar South Pole habitats and provide a continuous line-of-sight to the polar region. We describe the convergence characteristics of pole-sitter families and the feasible domain over which they may be computed. We find two dominant families of pole-sitters and derive an analytical description of the feasible region which is accurate for low-period pole-sitters.