Transfers from near-rectilinear halo orbits to low-perilune orbits and the Moon’s surface

Abstract

Near-rectilinear halo orbits (NRHOs) are periodic orbits that belong to the families of halo orbits around the L1/L2 points in a three-body system and have low minimum distances to the smaller primary. NRHOs possess some good dynamical and geometrical properties and are now considered as potential orbits for a near-future crewed deep space station. Recently, intensive investigations have been performed with regard to different aspects of a lunar NRHO mission: Earth-NRHO transfers, station keeping, shadow avoidance, and ground station visibility conditions are deeply studied. At the same time, the important operation of soft lunar landing from the working NRHO is still poorly covered in literature. In this research, we analyze both the direct landing scenario and the option of a transfer from the working NRHO to the intermediate low-perilune orbit (LPO). This kind of orbit can serve as a platform for transport communication between the lunar surface and the working NRHO. Lunar regions attainable after a one-impulse NRHO departure maneuver are identified, and the costs required for the soft landing are analytically estimated based on the classical gravity-turn landing strategy. In the scenario of a two-impulse transfer to the intermediate LPO, a wide range of perilune distances and inclinations is proved to be available. Several resonant NRHOs have been considered as a working orbit: the 4:1 and 9:2 L2 orbits, and the 11:3 L1 orbit. The calculations are performed in a high-fidelity model of motion that includes the JPL's DE430 ephemeris model of the Solar system and solar radiation pressure. The lunar gravitational field is evaluated based on the GRGM1200A spherical harmonic model truncated to degree and order 8.