Passive orbit control for space-based geo-engineering

In this Note we consider using solar sail propulsion to stabilize a spacecraft about an artificial libration point. It has been demonstrated that the constant acceleration from a solar sail can be used to generate artificial libration points in the Earth-Sun three-body problem. This is achieved by directing the thrust due to the sail such that it adds to the centripetal and gravitational forces. These libration points have the potential for future space physics and Earth observation missions. Of particular interest is the possibility of placing solar reflectors at the L1 artificial libration point to offset natural and human driven climate change. One engineering challenge that presents itself is that these artificial libration points are highly unstable and require active control for station-keeping. Previous work has shown that it is possible to stabilize a solar sail about artificial libration points using variations in both pitch and yaw angles. However, in a practical sense, solar sails are large structures and active control of the sail's attitude is a challenging engineering problem. Passive stabilization of such reflectors is to be investigated here to reduce the complexity of space-based geo-engineering schemes