Daily-repeat stereo monitoring from formation flying

Three satellites in formation flying have the flexibility to monitor the target on the ground and the vicinity in the space, and can even achieve stereo view for any object. We consider each satellite orbit is slightly different with a daily-repeat circular Sun-synchronous orbit in the inclination, the right ascension of ascending node, the argument of perigee, and the mean anomaly. According to the linearized orbit equation, a formation of a tilted triangle with respect to the equatorial plane can be constructed. A Sun-synchronous formation is then obtained through a rotation. We investigate the maintenance cost through the evaluation of the delta-V for the triangle formation under perturbation by the PID autonomous control of the nonlinear equation of motion. With reference to the relative position with respect to the formation centroid, the formation configuration can be maintained with less delta-V.

► Sun-synchronous formation is constructed according to the linearized orbit equation.
► Nonlinear equation of motion for the formation with PID control is investigated numerically.
► Using control with respect to its centroid, the formation can be maintained with less delta-V.