Formation flying around displaced orbit

The solar sails formation flying around displaced orbit is investigated in this paper. Considering that the relative distance between two sails is very small compared to the distance between the Sun and the sails, linear time invariant relative motion equations are obtained when the first order approximation is applied. The qualitative characteristic and stability of relative motion are obtained according to the linear equations. At last, the algorithm for calculating the periodic solution of original nonlinear equations is given. The initial values of natural formation flying are also given.