Evaluation of Orbit Errors and Measurement Corrections in Differential Navigation with LEO Satellites

Joe Saroufim, Samer Hayek, and Zaher M. Kassas

Peer Reviewed

Abstract: Ephemeris errors and measurement corrections in differential navigation with low Earth orbit (LEO) space vehicles (SVs) are analyzed. First, orbit errors are characterized for the non-differential case, showing the dependency of the range measurement errors on the receiver-to-SV geometry. The study is then extended to the differential case, where the maximum differential range error is found to occur when the baseline is normal to the projected measurement vector from one receiver onto the local navigation frame. A simulation study is presented to assess the differential navigation performance with 14 Starlink and 11 OneWeb LEO satellites. The framework fused differenced pseudorange measurements from a base and rover to LEO SVs with inertial measurement unit (IMU) measurements via an extended Kalman filter (EKF) in a tightly-coupled fashion to estimate the rover’s states. The simulation considered an aerial vehicle equipped with a tactical-grade IMU, an altimeter, a GNSS receiver, and a LEO receiver making pseudorange measurements to the LEO SVs. During 300 seconds of flight time, the vehicle traveled a distance of 28 km, the last 23 km of which were without GNSS, achieving a three-dimensional (3-D) position root mean squared error (RMSE) of 52 cm, compared to 12.5 m using the non-differential framework. Experimental results are presented, showing the potential of differential navigation in reducing ephemeris, clocks, and atmospheric errors. A ground vehicle traversed a distance of 540 m in 60 seconds, the last 492 m of which without GNSS signals, while making Doppler measurements to 2 Orbcomm and 1 Iridium LEO SVs, whose ephemerides were obtained from two-line element (TLE) files, propagated with simplified general perturbation 4 (SGP4) orbit propagator. The differential framework yielded a position RMSE of 7.13 m, compared to 41.29 m using non-differential measurements, and 87.74 m with GNSS-aided IMU.
Published in: Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023)
September 11 - 15, 2023
Hyatt Regency Denver
Denver, Colorado
Pages: 2823 - 2834
Cite this article: Saroufim, Joe, Hayek, Samer, Kassas, Zaher M., "Evaluation of Orbit Errors and Measurement Corrections in Differential Navigation with LEO Satellites," Proceedings of the 36th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2023), Denver, Colorado, September 2023, pp. 2823-2834. https://doi.org/10.33012/2023.19452
Full Paper: ION Members/Non-Members: 1 Download Credit
Sign In