Orbital formationkeeping with differential drag

This paper examines the feasibility of using differential drag between two spacecraft as the means for controlling their relative positions. The equations ofirelative motion between two satellites are derived and a coordinate transformation is made to reduce the formationkeeping problem to the simultaneous solution of a double integrator and a harmonic oscillator. A simple feedback control law is developed that simultaneously and dependently solves the double integrator and harmonic oscillator; the control law consists of two parts: the main control law and the eccentricity minimizing control scheme. Results are presented of four test cases which show that the control law can drive a satellite from an initial position to a target position and maintain the satellite at that location.