Earth resonant gravity assists for asteroid retrieval missions

Asteroids and comets are of strategic importance for science in an effort to uncover the formation, evolution and composition of the Solar System. Near-Earth objects (NEOs) are of particular interest because of their accessibility from Earth, but also because of their speculated wealth of material resources. The possibility of retrieving entire NEOs from accessible heliocentric orbits and moving them into the Earth’s neighbourhood is today a credible possibility considered by NASA, within its Asteroid Initiative Framework, and examined in several recent scientific publications. This paper searches for asteroid retrieval trajectories that benefit from several resonant Earth encounters to decrease at each encounter the transfer ¿v cost. Particularly, the paper focuses on the Amor asteroid population, which have the encounters always occurring outside the Earth’s sphere of influence. Thus, the patched conic approximation is rendered essentially not applicable. Numerical exploration in the framework of the Circular Restricted Three Body Problem (CR3BP) becomes computationally expensive when combined with the sensitivities of multiple Earth encounters. Hence, this paper proposes a 3D extension of the energy kick function to rapidly assess all possible third-body effects into the asteroid’s trajectory. The osculating elements of the asteroid can be updated by means of Picard’s first iteration on each Keplerian element, where the perturbing forces of the third body (i.e., the Earth) are given by the Lagrange’s planetary equations. This allows a rapid scanning process of sequences of Earth encounters that may in turn allow a favourable perturbation to the asteroid orbital elements.Peer Reviewe