Relative Navigation Performance of LEO Vehicles Considering GPS–KPS Constellation and Measurement Characteristics

This paper proposes a method for relative navigation between two satellites in low-earth orbit (LEO) using the global positioning system (GPS) and Korean positioning system (KPS). The extended Kalman filter (EKF) is designed using pseudorange and Doppler single differences from GPS and KPS, as well as inter-satellite link measurements. The designed EKF accurately estimates relative position, velocity, receiver clock biases, and drift. Measurement noise at a level suitable for the space environment and process noise based on the stability specifications of the receiver clock are modeled. The effectiveness of the proposed method is validated through simulations, and the results of relative navigation based on GPS, a mid-Earth orbit constellation, and KPS-based relative navigation, a geosynchronous orbit constellation, were analyzed. The relative position error showed a precision of cm level, and the relative velocity error showed a precision of mm/s level. The proposed algorithm can effectively estimate the relative position and velocity between two satellites in LEO.