Dynamics and control for spacecraft tracking a displaced orbit around an asteroid exploiting solar sail

This study investigates the displaced orbit around a near-Earth asteroid for spacecraft achieved via a realistic solar sail with a performance based on the existing technology in a low distance. Using the realistic solar sail to achieve the displaced orbit with a short displaced distance is more difficult compared with using a traditional thruster under two main limitations: The force limitation and the position limitation. Firstly, the solar radiation pressure (SRP) force generated by the solar sail is limited by the solar sail’s property and the sunlight direction. Therefore, the feasibility of maintaining a displaced orbit at an equilibrium point around the asteroid at a low distance using a solar sail with realistic performance is investigated analytically. The results demonstrate that the equilibrium point of the displaced orbit can be achieved. Secondly, the usage of the solar sail is also limited by the position of the spacecraft. The SRP force cannot be generated in the eclipse region wherein sunlight is absent; specifically, in a displaced orbit with a low displaced distance, the position limitation is more notable. To address this challenge, spacecraft dynamics and control using a solar sail are investigated to achieve the displaced orbit, and a method of orbit transfer outside the eclipse region is proposed. Numerical simulations reveal that the spacecraft can maintain the displaced orbit using the solar sail without entering the eclipse region. Moreover, spacecraft can achieve orbit transfer between two equilibrium points without entering the eclipse region by using the solar sail. The impact of non-spherical shape of the primary asteroid is also investigated. Results show that the proposed method can maintain a displaced orbit with errors from the reference state less than 10 % during a limited time span when the primary asteroid has a non-spherical shape.