A stable heliocentric disposal strategy for LPO missions, inspired by the natural co-orbital motion of Saturn's moons

In this work, we present a disposal strategy for Sun-Earth LPO missions, based on stable heliocentric graveyard trajectories that do not approach the Earth-Moon system in the long term. Previous studies analyzed the possibility of reentering to the Earth, impacting on the Moon or move to a heliocentric graveyard orbit. The novelty of our work is that we take advantage of the mutual configuration observed in nature between Janus and Epimetheus, two moons of Saturn, to design a heliocentric graveyard strategy that is stable in the long term and does not require additional operations to stay away from the Earth. Rather than lowering the energy of the spacecraft (or increasing the Jacobi constant) to close the zero-velocity curves, the configuration needs an energy increase to reach a trajectory that encompasses L3, L4 and L5. Taking advantage of the theory developed to explain the motion of Janus and Epimetheus, we design horseshoeshaped orbits, that satisfy the conditions required to be stable under the dominant orbital perturbations. The stability of these disposal orbits is verified considering a n-body problem with solar radiation pressure. The transfer required to move from a given L2 LPO mission to such orbits can be designed exploiting the unstable invariant manifold of the L2 orbit.