Design and Analysis of a Formation Tracking Controller for Future Space Interferometer Missions

Spacecraft formation flying is essential for space-based interferometry missions detecting gravitational waves, such as LISA, DECIGO, and the upcoming Japanese SILVIA mission. These missions require strict requirements of relative positions between spacecraft to guarantee accurate measurements. This thesis focuses on trajectory tracking for three spacecraft orbiting a General Circular Orbit (GCO). The goal is to maintain accurate relative distances despite initial perturbations and external disturbances, including J2 force perturbation and drag force. Three nonlinear control strategies are investigated: Passivity-Based Control (PD), First-Order Sliding Mode Control (FOSM), and Boundary Layer First-Order Sliding Mode Control (BLFOSM). Numerical simulations evaluate each method under realistic conditions. While Passivity Based Control and Sliding Mode Control both achieve good tracking accuracy, Sliding Mode exhibits chattering, and Passivity-Based Control demands high control effort. In contrast, Boundary Layer Sliding Mode reduces both chattering and control effort, and when combined with an adaptive sliding surface, it achieves faster convergence and the highest overall tracking accuracy. These results demonstrate the feasibility of high-precision formation flying and provide guidance for designing robust control strategies in future space interferometry missions.