Disposal Strategies for Spacecraft in Lagrangian Point Orbits

This work presents three different strategies for the disposal of Lagrangian Point Orbit (LPO) missions that have been analyzed in the frame of the European Space Agency study "End-of-life disposal concepts for Lagrange-points and HEO missions". The first strategy analyzes a Moon impact scenario, the second one a reentry in Earth's atmosphere, whereas the third concerns the injection into heliocentric graveyard orbits. For Moon impact and Earth's reentry an optimization problem is set up to minimize the propellant consumption while satisfying constraints on terminal position. For the graveyard, two methods are proposed: the first is a fully numerical approach based on the solution of an optimization problem via genetic algorithms, whereas the second one is based on the Jacobi constant and on a tangential disposal maneuver designed to close the Hill's regions. In this paper, solutions compatible with mission constraints are presented for SoHO and GAIA.