An Autonomous Planetary Navigation System Independent of GNSS and Ground Station Tracking

When ground station tracking or Global Navigation Satellite System (GNSS) signals are not readily available, orbit determination can be challenging. For these situations, a computationally efficient and autonomous navigation system that is independent of these update sources is proposed. This navigation system involves two satellites, designated Chief and Deputy. The Chief is equipped with a star camera and can measure the relative position of the Deputy. Using an Extended Kalman Filter (EKF) equipped with a second-order zonal harmonic gravity model and Gravity Model Error Compensation (GMEC), absolute position and velocity estimates of the Chief and Deputy can be obtained near any celestial body. Despite the low fidelity of the second-order zonal harmonic gravity model, we show that the GMEC technique used in this study enables accurate orbit determination of both satellites in the absence of a high-fidelity gravity model. As a result, this navigation system becomes feasible to implement aboard small satellites which can be computationally constrained. Through performance demonstrations in various geocentric and Lunar orbits, we show that our navigation system is well suited for cislunar and deep space navigation.