Near-optimal capture in the planar circular restricted Pluto-Charon system

In this paper, the near-optimal capture problem is numerically investigated to locate the optimal capture points around Charon using the Pluto-Charon planar circular restricted three-body problem (PCRTBP). Capture orbits are divided into the pre- and post-maneuver portions. In the pre-maneuver portion, the gravitational capture conditions are discussed by backward numerical integration. In the post-maneuver portion, the smaller alignment index (SALI) is applied to numerically investigate the orbital characters of long-term capture orbits around Charon. The initial conditions corresponding to three types of motion: (i) bounded (regular or chaotic), (ii) escaping and (iii) collisional are classified and studied. Combining results of the pre- and post-maneuver portions, the near-optimal capture method is presented to find optimal capture points by overlay figures, and then the corresponding capture orbits are constructed in the PCRTBP. The different results between the Pluto-Charon system and the Earth-Moon system are compared and analyzed. Our results obtained in this paper, including the optimal capture points and the corresponding capture orbits, could be applied in future space mission design.