Closed-loop orbit transfer using solar electric propulsion

A closed-loop control method for the solution of the multirevolution transfer from low Earth orbit to geostationary orbit with very low thrust is presented. Results of the orbit transfer for three different cases (LEO to GEO, LEO to MEO, and GTO to GEO) are shown. In all cases, transfer is achieved with results that compare favorably to those obtained with traditional optimization methods in terms of the transfer time. Results of the circular-to-circular transfers are close to optimal, both in terms of time and fuel consumption. The closed-loop control is of simple and direct implementation, requiring the real-time knowledge of the spacecraft position and velocity with respect to Earth. The closed-loop control is an effective real-time solution with all well-known characteristics of feedback solutions. It is robust, needs no lengthy and complex optimization, and naturally copes with unmodeled effects, as well as changing operating characteristics of real propulsion systems. This closed-loop control law enables the satellite to implement the transfer from any closed orbit to any circular orbit.