Passive control of displaced solar sail orbits

An analysis of the linear stability and control of families of displaced solar sail orbits is presented. Three families of orbits are reviewed along with their linear stability characteristics. It is then shown that the unstable subfamilies of orbits that exist are controllable using state feedback to the sail attitude. However, a more useful result is presented that demonstrates that linear stability can be achieved if the sail attitude is fixed relative to the sun-sail line. Such an attitude can be achieved by passive means by a suitable choice of sail shape. Therefore, the subfamilies of unstable orbits can in principle be stabilized by fully passive means. Such passive control is clearly useful for simplifying station-keeping on such orbits.