On the effects of Sun's gravity and solar radiation pressure to the Earth-Moon distant retrograde orbits

The distant retrograde orbits(DROs) form a family of planar periodic orbits that are retrograde around the Moon in the Earth-Moon circular restricted three-body problem(CR3BP). Known for their "low-energy insertion, long-term stability, and global accessibility", DROs are regarded as ideal candidates for future cis-lunar exploration. Sun's gravity and solar radiation pressure(SRP), as primary perturbations in the Earth-Moon system, could significantly alter the orbit dynamics of spacecraft. Based on the above considerations, the effect of the Sun's gravity and SRP on the dynamics and geometry of Sun-resonant DROs within a quasi-bicircular problem(QBCP) is investigated. Each resonant DRO in the CR3BP bifurcates into at least two branches in the QBCP. Furthermore, the Sun's gravity can qualitatively alter the phase-space structure of most resonant DROs, transforming them from stable to unstable, which opens the possibility of low-energy transfer. Regarding SRP, it induces more complex changes in the phase-space structures and leads to more bifurcation types, such as tangent bifurcation, period-doubling bifurcation and second-class Hopf bifurcation, thus deriving richer families of orbits. It is worthily noted that SRP may help stabilize orbits, making it beneficial for station-keeping. Additionally, SRP can significantly alter the geometry of DROs. Especially when the spacecraft which has a relatively large lightness number, is pitched at certain angles, the planar DROs evolve into spacial orbits to make them more suitable for cis-lunar space missions.