State Estimation for Spacecraft Formation Flying Based on the Separation

The requirements for autonomous satellite formation flying in tight configurations, has given rise for the identification of reliable controllers using linearized relative dynamics equations that include nonlinear perturbations and more realistic scenarios. In this paper, a controller for close-manoeuvring, spacecraft in formation equipped with collision-avoidance capabilities, is presented using a state estimator built on the forward-in-time separation principle. The separation principle allows the observer and the controller to be designed independently, by exploiting the advantages of the linear quadratic regulator theory (LQR), in order to estimate the states of a nonlinear dynamical system with model and sensor uncertainty. The proposed dynamical model accounts for both circular and eccentric reference orbits and incorporates accelerations from an artificial potential field, in order to perform evasive actions during proximity manoeuvring. Moreover, test cases based on the Prototype Research Instruments and Space Mission Technology Advancement (PRISMA) will be implemented, comprising multiple spacecraft transfers and on-orbit position switching. The results obtained will be compared against the performance of an LQR-based controller (LQRC) previously designed by the authors for ideal scenarios, showing that the proposed controller provides similar performance to that obtained by the LQRC in terms of time of convergence, manoeuvre delta-v and fuel consumption.