Analysis of Preliminary Impulsive Trajectory Design for Near-Earth Asteroid Missions under Approaching Phase Constraints

This study investigates the preliminary trajectory design for high-thrust missions to near-Earth asteroids (NEAs), considering distance and phase angle constraints during the approaching phase to enable pre-rendezvous optical navigation and the scientific identification of asteroids. A global optimization algorithm called monotonic basin hopping is used to design (Formula presented.) -optimal impulsive trajectories both with and without constraints. Comparisons reveal that extending the final leg of the unconstrained reference trajectory and incorporating a few deep-space maneuvers in that final leg can yield a constrained trajectory with a (Formula presented.) increase of only a few percent. The effects of the phase angle and minimum distance constraint on (Formula presented.) are also examined. The results indicate that in (Formula presented.) -optimal constrained trajectories, an additional deep-space maneuver enables the redistribution of maneuvers in the last leg to ideally insert the spacecraft into the constraint cone. However, additional small maneuvers may be necessary at times to ensure that the spacecraft remains within the cone. Based on these findings, we present a two-step approach for the preliminary design of constrained trajectories for NEA missions based on global optimization algorithms. This approach serves as a valuable tool for initial mission design and trade-off analyses involving constraints, fuel usage, and transfer durations.