Investigating the control design of the disturbance reduction system for the LISA mission

The Laser Interferometer Space Antenna (LISA) mission will consist of a three spacecraft formation acting as a large interferometer. The spacecraft formation will measure the distortion of space caused by passing gravitational waves. Each spacecraft will contain two shielded proof masses that define the optical arms of the interferometer. To mitigate the effects of external disturbances, the LISA Disturbance Reduction System will control the spacecraft to fly drag-free trajectories with reference to their respective proof masses. This paper investigates control design issues associated with the LISA Disturbance Reduction System (DRS). In particular, this paper presents a two degrees-of-freedom (DOF) model representing a spacecraft with a single proof mass. With this model, key control design issues are identified. A Linear Quadratic Gaussian (LQG) controller design is then presented to illustrate the feasibility of the DRS control concept. A three DOF model is used to explore the DRS implications of a spacecraft with two proof masses.