In this paper, we consider a linear quadratic regulator control problem for spacecraft rendezvous in an elliptical orbit. A new spacecraft rendezvous model is established. On the basis of this model, a linear quadratic regulator control problem is formulated. A parametric Lyapunov differential equation approach is used to design a state feedback controller such that the resulting closed-loop system is asymptotically stable, and the performance index is minimized. By an appropriate choice of the value of a parameter, an approximate state feedback controller is obtained from a solution to the periodic Lyapunov differential equation, where the periodic Lyapunov differential equation is solved on the basis of a new numerical algorithm. The spacecraft rendezvous mission under the controller obtained will be accomplished successfully. Several illustrative examples are provided to show the effectiveness of the proposed control design method.OPTIMAL CONTROL APPROACH TO SPACECRAFT RENDEZVOUS 159 As it is well known, the propellant storage capacity of a spacecraft rendezvous system is very small. Thus, it is important to reduce fuel consumption in the spacecraft rendezvous process. Once the chaser spacecraft runs out of fuel, the spacecraft rendezvous mission will no longer be possible to continue. Thus, the minimization of the fuel consumption during the spacecraft rendezvous mission is critically important. Consequently, the minimum fuel consumption problems in spacecraft rendezvous have been actively studied among the control community. For instance, the minimum fuel rendezvous problem is studied in [8], where the spacecraft is driven by normal power; a minimum fuel consumption for spacecraft rendezvous problem in a general central gravity force field is investigated in [9]; a minimum fuel consumption problem subject to constraint on the inverse square field is considered in [10]; low-thrust optimal rendezvous maneuver in the vicinity of an elliptical orbit is studied in [11]; differential game theory is applied in [12] to achieve the optimum lowacceleration rendezvous maneuver for spacecraft rendezvous; an exact penalty function method is used in [13] to solve a fuel optimization problem for continuous-thrust orbital rendezvous subject to collision avoidance constraint. However, the optimal control methods mentioned previously are for the design of open-loop controllers. It remains a challenge to design optimal closed-loop controllers, which are much preferred in engineering applications.In this paper, we consider a linear quadratic regulator (LQR) control problem. The nonlinear spacecraft rendezvous system is first linearized around the origin, resulting in a linear time-varying system. By considering the true anomaly as a new variable, the linear time-varying system is transformed into a linear periodic system. A parametric Lyapunov differential equation approach is proposed to design a state feedback controller such that the resulting closed-loop system is asymptotically stable, and the performance index is minimize...