Periodic orbits high above the ecliptic plane in the solar sail 3-body problem

Due to the non-central nature of the force on a solar sail, there exist equilibrium points of the equations of motion out of the ecliptic plane in the Sun-Earth-Sail circular restricted 3-body problem, in contrast with the classical Lagrange points. Analogous to the 'halo' orbits, we construct large amplitude periodic orbits about these equilibria. By timing the period of the orbit we may negate the seasonal effects of the variation in the Earth's axis of rotation, and thus the sail's position when viewed from the pole subtends a much smaller angle (around 8 deg rather than 46 deg). These orbits are of practical interest with regards to communication with, and constant imaging of, the poles.