Two-Impulse Transfers from Lunar Distant Retrograde Orbits to Resonant Orbits

As unique types of orbits in the cislunar space, distant retrograde orbits (DROs) and resonant orbits (ROs) are of great significance in future cislunar explorations, and the transfer between them deserves special attention. The design of transfer trajectories between these two kinds of orbits remains a challenge due to their stability. In this study, a novel transfer pathway from DROs and ROs is constructed based on a search and optimization methodology, which could offer an alternative for mission design related to these two orbits. Two-impulse transfers for both planar and nonplanar cases are designed in the circular restricted three-body problem, and three types of transfer orbits are obtained and characterized, including the direct transfer, the lunar gravity assisted transfer, and the external transfer. Planar transfers are also refined in the bicircular restricted four-body problem in consideration of the solar gravity. Furthermore, representative transfer orbits are transitioned into the ephemeris model to validate the preliminary design, and the result indicates that the transfer cost fluctuates with different departure epochs for all types of transfers.