GNSS-Based Relative Navigation for Two Satellite Formation Under Uncertainty Using Three-EKF Architecture

The concept of satellite formation flying in a stochastic environment involves the coordinated movement of multiple spacecraft. This coordination is aimed at achieving a unified objective. This research proposes an autonomous relative navigation approach for dual satellite formations utilizing a three Extended Kalman Filter (EKF) based on Global Navigation Satellite System (GNSS) data. The proposed methodology involves estimating the states of the mother and follower satellites using nonlinear GNSS measurements and Keplerian orbital elements, incorporating J2 perturbations. The differences in state estimates between the mother and follower satellites serve as inputs to the EKF, facilitating estimation of relative satellite states. Furthermore, a novel approach integrates the state vectors derived from three EKFs utilizing the Hill-Clohessy-Wiltshire (HCW) relative motion model, enhancing accuracy by accommodating satellite motion perturbations.