Bouncing return trajectory design for precise lander deployment to asteroids

This paper investigates a novel method to increase the accuracy of ballistic deployment by controlling the spin rate of the lander, assuming that the lander is spherical. The concept of the bouncing return trajectory is proposed, which takes off and lands at the same point on the asteroid surface. The spin rate of a spherical lander is controlled before each impact to change its postimpact velocity so that it can be driven into the bouncing return trajectory and remains in the vicinity of its original landing site until it finally rests on the surface. First, the properties of bouncing return trajectories are investigated based on a spherical model. Based on the contact dynamics, the analytical solution of the required spin rate to change velocity is derived. Next, candidate deployment trajectories of the proposed method are studied under different asteroid parameters. Finally, the feasibility and robustness of the method are verified using a model of the asteroid Bennu. It is found that the proposed deployment method can achieve a precise landing if the surface environment is ascertained and largely reduce the landing dispersion under an uncertain environment. This paper provides a novel idea for future asteroid lander deployment and surface exploration missions.