Alternating orbiter strategy for asteroid exploration

This paper proposes the use of highly non-Keplerian trajectories enabled by solar radiation pressure and devices with variable area or reflectivity to map and characterize small asteroids. Strategies alternative to hovering involving a combination of retrograde and prograde orbits, together with inversions of the orbit direction by either maneuvers or exploiting the natural dynamics, are presented and analysed. As opposed to terminator orbits, this alternating orbiter strategy allows direct overflies of the subsolar point and other equatorial regions. A simple cost comparison demonstrates a significant improvement with respect to traditional hovering strategies. Additional orbits of interest for hopper spacecraft are also discussed. Finally, various possible implementations of variable-area spacecraft that could provide the required solar radiation pressure control are suggested and discussed.