Strategies to capture asteroids to distant retrograde orbits in the Sun–Earth system

Abstract

Capturing near-Earth asteroids would be of great significance for future space missions. Due to its stability, distant retrograde orbit (DRO) around the Earth has the potential to be an ideal destination for the captured asteroids. In this paper, we propose three strategies to capture asteroids to DROs in the model of the circular restricted three-body problem in the Sun–Earth system. In the manifold-assisted strategy, Lyapunov orbits that are tangential to DROs are calculated, and then stable manifolds are employed to design transfers for capturing asteroids. The non-coplanar Hohmann transfer is used to guess the total cost of capturing an asteroid, and candidate asteroids are thus selected. The second strategy of asteroid capture is defined as direct capture to increase opportunities of capturing asteroids with low cost. The captured asteroid can be inserted into the target DRO with a maneuver at any position along the DRO. Then optimal results are obtained after analyzing the capture conditions. Finally, a strategy of using a flyby of the Earth is proposed as the power Earth-flyby capture, and an additional maneuver is imposed on an asteroid at the perigee of the transfer trajectory. Results show that the direct and powered Earth-flyby asteroid capture strategies potentially need fewer velocity increments than the manifold-assist strategy. Furthermore, 2020SO can be captured into DROs with lower energy than the other candidate asteroids in three capture strategies, and the minimum cost is approximately 189.93 m/s.