PROCYON Mission Reanalysis: Low-Thrust Asteroid Flyby Trajectory Design leveraging Convex Programming

PROCYON is the world's first deep-space micro spacecraft launched on December 3, 2014, as a secondary payload on the launch of JAXA's Hayabusa2 spacecraft. The mission objectives include the high-speed flyby observation of a near-Earth asteroid, which is enabled by utilizing miniature electric propulsion and an Earth swing-by. Through the PROCYON mission design, we encountered a limitation with the zero-radius sphere-of-influence patched-conics approach used in typical mission design. The patched-conics approach could not find a trajectory toward 2000 DP107, the nominal target asteroid, which is attainable only by a distant Earth swing-by under multi-body dynamics. This limitation mainly comes from the low orbital control capabilities of small spacecraft systems. To overcome this difficulty, we propose a preliminary mission design method that quickly calculates low-thrust and gravity assist trajectories using a convex programming approach. The method enables us to search for reachable asteroids extensively under multi-body dynamical systems. We reanalyze the PROCYON mission by the proposed mission design procedure and broadly perform trade studies regarding candidate asteroids in terms of transfer costs and operational requirements. The numerical result demonstrates that the proposed method efficiently finds the nominal target that we could not find by the patched-conics approach.