Abstract: The problem of maintaining control is investigated for the hybrid propulsion spacecraft formation around the displaced solar orbit. Firstly, the equation of the formation around the displaced solar orbit for relative motion is derived. Since the changing of the displacement between two different spacecrafts is small and the displacement between two different spacecrafts is very small compared with the displacement from the spacecrafts to the sun, the equation of motion is linearized around the displaced solar orbit. Based on the linear equation, the linear quadratic regular (LQR) is designed. This control method which responds fast and is easier to control can change or maintain the formation configuration by adjusting the attitude of the solar sail and the Coulomb force between the spacecrafts. Simulations are given based on the linear equation. The results show that the strategies can realize the formation around the displaced solar orbit.

Key words: solar sail, displaced orbit, Coulomb force, formation maintaining, linear quadratic regular