Moon-Centered Orbit

Author: Tianjiang Shuo

Website: https://cislunarspace.cn

Definition and Classification Position

A moon-centered orbit is a periodic orbit around the Moon that can be continued from initial guesses of the lunar two-body problem — prograde or retrograde alike (He 2026). In periodic-orbit classification, moon-centered orbits stand alongside libration point orbits and resonant orbits (He 2026, Folta 2015).

Three Member Families

Moon-centered orbits comprise three families, corresponding respectively to the f, g, and g′ families of Hénon 1969 (the periodic-orbit classification of Hill's case) (He 2026):

• DRO (distant retrograde orbit, f family): retrograde around the Moon in the rotating frame; as amplitude grows it can extend beyond L1/L2 — see Distant Retrograde Orbit (DRO).
• DPO (distant prograde orbit, g family): figure-eight-shaped in the rotating frame, with perilune close to the Moon and apolune extending along the y direction.
• LoPO (low prograde orbit, g′ family): prograde, nearly circular, low-amplitude orbits; as amplitude grows the apolune extends along the x direction.

Engineering Members: Low Lunar Orbit and Lunar Parking Orbit

The moon-centered orbit most used in engineering is the low lunar orbit (LLO) / lunar parking orbit — a two-body nearly circular orbit rather than a three-body orbit family. Typical usage: a near-circular orbit 100 km above the lunar surface serves as the parking orbit; a large-amplitude L1 Lyapunov orbit tangent to it can enter the parking orbit directly with a single tangential braking impulse at the tangent point (on the x-axis) (Zheng & Zhao 2023). This mechanism constitutes an Earth–Moon low-energy transfer in which "one manifold connects near-Earth and near-Moon orbits" (see Low-Energy Transfer).

Transfer Construction via Manifold Intersections with Lunar Periodic Orbits

Giancotti 2012 introduced a cylindrical isomorphic mapping in the planar CR3BP, reducing the state at a given Jacobi constant to the (x, y, γ) phase space (γ being the velocity direction angle), so that a lunar periodic orbit and the unstable manifold of an L1 Lyapunov orbit can be compared in the same space; along their intersection set one takes the minimum impulse that "only rotates the velocity vector without changing its magnitude." In the example (a single-revolution lunar periodic orbit at C=3.185), the best transfer from the L1 Lyapunov orbit costs only 18.71 m/s.

Related Umbrella Term

"Near-Moon periodic orbits" is a cross-category umbrella term selected by distance from the Moon — its members span libration point orbit families (halo, Lyapunov, butterfly) and moon-centered orbit families (DRO, LoPO) (Qi & Oguri 2023, used for comparing optical autonomous orbit determination performance: the periapsis–apoapsis distance difference sets the range of lunar apparent diameter variation, which in turn affects determination performance). It is not the same level of concept as "moon-centered orbit" — distinguish the two when citing.

Terminology Variants

Related Concepts

• Distant Retrograde Orbit (DRO)
• Quasi-Satellite Orbit (QSO)
• Lyapunov Orbit
• Low-Energy Transfer

References

• Hénon, 1969, Numerical exploration of the restricted problem. V. Hill's case
• Giancotti, Pontani & Teofilatto, 2012, Lunar capture trajectories and homoclinic connections through isomorphic mapping
• Folta et al., 2015, An Earth-Moon system trajectory design reference catalog
• Qi & Oguri, 2023, Analysis of autonomous orbit determination in various near-Moon periodic orbits
• Zheng & Zhao, 2023, Earth–Moon transfer method based on the stable manifolds of large-amplitude Lyapunov orbits
• He et al., 2026, A review of cislunar constellation design and optimization