Design of optimal spatial low-energy trajectories to Near Earth Objects

Near Earth Objects (NEOs) are small Solar System bodies (such as asteroids, comets and meteoroids) in heliocentric orbits with perihelion below 1.3 astronomical units. With a catalog of over 30, 000 known asteroids and approximately 100 listed short-period comets, the NEO population represents an inventory of exploration targets reachable with significantly lower cost than the objects of the Main Asteroid Belt. Similarly to the latter, NEOs are primordial bodies, hence their study can provide insight into the origins of our planetary system. In addition, the materials present in these objects can be used to resupply spacecraft on course to other destinations. Past missions to NEOs, such as NEAR, Hayabusa, ICE, and Deep Impact, have traditionally used the patched-conics approximation, often combined with impulsive and/or low-thrust maneuvers. This contribution builds on a previous work which proposed a novel design technique that leverages the invariant dynamical structures of the planar circular restricted three-body problem (CR3BP) and the efficiency of the Keplerian approximation to connect the vicinity of the Earth with NEOs in nearly circular, low-inclined heliocentric orbits through planar Lyapunov orbits around the collinear points L1 and L2 of the Sun-Earth CR3BP. The resulting trajectories follow low-energy paths; therefore, they naturally minimize the launch cost. In this contribution, we develop an extension of the technique to the 3D domain, using libration point orbits with their hyperbolic invariant manifolds and an adaptation of a trajectory design method called MMAT to approach NEOs on inclined orbits. We evaluate key parameters such as time of flight, launch energy and ΔV to perform rendezvous with a variety of targets, and compare our results with existing solutions and past missions. Finally, we present a methodology to reshape the rendezvous maneuver using low-thrust arcs.