Bio-inspired guidance method for a soft landing on a Near-Earth Asteroid

Abstract

Achieving a soft landing over the surface of small celestial bodies is an essential maneuver in space to advance the status of space exploration, sample collecting and in-situ resource utilization, among other on-orbit tasks. Landing on these bodies is challenging due to the reduced-gravity and airless environment. The correct planning of execution of the trajectory to land on the surface of the body is of cumbersome importance to prevent the vehicle from bouncing up and eventually reach escape velocity. In this paper, a bio-inspired trajectory planning method to land on the surface of a Near-Earth Asteroid (NEA) with zero relative velocity is proposed. The method is based on Tau theory, which has been demonstrated to explain the way that humans and some other animals’ approach to different target spots to perform tasks such as perching, landing, and grasping. We have selected the NEA Apophis asteroid as our case study due to its accessibility, and small rotational velocity and orbit condition code. Two landing scenarios are studied; one considers the case where the satellite is hovering at a low altitude; the other corresponds to a landing maneuver right after a deorbiting or breaking phase, which may cause residual initial velocity in the vehicle prior to the landing maneuver. Once the descending trajectory is obtained, a closed-loop controller is in charge of achieving trajectory tracking and calculating the continuous and on/off thrust control signals. The simulation results show that the introduced approach can achieve zero final relative velocity in both cases for different initial condition, which is a requirement for a soft landing. Besides, different kinematic behaviors can be obtained by modifying the single variable named the Tau constant. The particular advantages of the method with respect to a commonly used approach are devised and analyzed as well.