Abstract: Distant Retrograde Orbit (DRO) is a family of large-scale, lunar-retrograde periodic orbits in the cislunar space. Due to its advantages of long-term stability, and low-energy transfer, DRO has become a potential orbit for many cislu-nar space missions. Investigating close formation techniques on DRO is of great significance for cislunar on-orbit servicing. Considering navigation and execution errors, it is essential to study the uncertainty propagation of close relative motion on DRO and design stationkeeping strategies. The fundamental solution set of linearized relative motion on DRO obtained through Floquet theory is introduced. Based on periodic solutions, analysis of position-velocity and safety uncertainty propagation of DRO formation flight is conducted using Cauchy-Green tensor and unscented transformation, respectively. Based on these analyses and considering engineering constraints, it was found that the maneuver frequency of 2 times per cycle and the maneuver locations at two perilunes is the near-optimal stationkeeping scheme. Following this, based on the relative motion perspective, an algorithm was de-signed for following reference trajectory. Based on the absolute motion perspective, an algorithm was designed to control the time of perilune passage. The simulation results show that both stationkeeping algorithms can ensure long-term safety and reasonable configuration of DRO close formation flight.

Key words: distant retrograde orbit, circular restricted three-body problem, relative motion, uncertainty propagation, sta-tionkeeping