Butterfly Orbit

Author: Tianjiang Shuo

Website: https://cislunarspace.cn

Definition

A butterfly orbit is a three-dimensional periodic orbit family among the libration point orbits, also called the P2HO1 family: it is born by period-doubling bifurcation from the NRHO segment of the L2 halo family (Grebow 2008, Zimovan-Spreen 2022). The orbit's projection is a figure eight whose two lobes lie on the Moon's L1 side and L2 side respectively, that is, the orbit wraps around the Moon across its two sides, rather than connecting the L1 and L2 libration points (Zimovan-Spreen 2022). The name comes from this butterfly/figure-eight shape (Grebow 2008).

Like the vertical orbit, motion along a butterfly orbit traces a figure eight, but it loops around the Moon's near and far sides, keeping the lunar south pole in view for almost the entire period (Grebow 2008).

Applications

• Polar coverage: a butterfly orbit combined with a 6–7.2-day L2 halo orbit at a 2:1 period ratio can build a lunar south pole coverage constellation (Grebow 2008's example pairs a 14-day butterfly with a 7-day halo).
• Transfer initial guesses: the butterfly family's manifolds are used to construct impulsive NRHO↔DRO transfers; an example patched via a 4:3 resonant arc costs about 0.50 km/s over 97 days (Zimovan-Spreen 2022).
• Phasing: the butterfly family takes part in the comparison as one of the candidate parking-orbit strategies for NRHO phasing (Bucchioni 2023).
• Space domain awareness: the southern/northern butterfly families are listed as candidate observer orbit families for cislunar space domain awareness (Klonowski 2024).

Related Concepts

• Halo Orbit
• Near-Rectilinear Halo Orbit (NRHO)
• Vertical Orbit
• Axial Orbit

References

• Grebow et al., 2008, Multibody orbit architectures for lunar south pole coverage
• Zimovan-Spreen et al., 2022, Dynamical structures nearby NRHOs with applications to transfer design in cislunar space
• Bucchioni et al., 2023, Phasing with near rectilinear halo orbits: design and comparison
• Klonowski et al., 2024, Cislunar space domain awareness architecture design and analysis for cooperative agents