Solar sail cooperative constellation control in displaced asteroid orbits

This paper presents displaced solar sail orbits around an asteroid with free angular coordinates. We propose to displace the orbit plane in the normal direction of the varying incident sunlight. Moreover, the angular coordinate along the orbit is uncontrolled to tackle the underactuated control problem of a two-angle-controlled solar sail. Such orbits allow only limited angular velocity to ensure controllability. Secondly, two constellation strategies based on leader-follower configuration are investigated: the loose strategy is based on sliding-mode-like method for orbit control and clock-angle switching for collision avoidance, and the tight one is based on using optimisation to solve boundary value problem. The advantage of the loose strategy is the computational simplicity and that of the tight one is the accuracy and inherent avoidance of collision. Using the loose one for orbit insertion control and finally applying the tight one for spacing adjustment enables the realization of a precise constellation reducing risk of collision.