Disposal of libration point orbits on a heliocentric graveyard orbit: the Gaia mission

This paper presents the options for Gaia disposal through transfer into a heliocentric graveyard orbit. The disposal manoeuvre sequence is designed in a high-fidelity dynamical model using an energetic approach written in the osculating restricted three-body problem. A first manoeuvre is given to leave the Libration Point Orbit, while a second manoeuvre is used to decrease the three-body problem energy of the spacecraft. The disposal design is optimised to maximise the distance from Earth for a period of 100 years and to minimise the possibility of gravitational interaction with the Earth, due to perturbation induced by other planets. Particular emphasis is given to the effect of the eccentricity of the Earth’s orbit around the Sun. The elliptical restricted three body problem formulation and the results in the full dynamics are used to show the dependence of the manoeuvre to the angular position of the Earth-Moon barycentre with respect to the Sun at the time of injection into the disposal trajectory. These findings are exploited to design a novel disposal strategy that is sustainable and minimises the chance of return to Earth on the long term.