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Session E3c: LEO for Positioning, Navigation, and Timing

Tracking GNSS-like Signals Transmitted from LEO Satellites and Propagated Through Ionospheric Plasma Irregularities
Jiawei Xu, Y. Jade Morton, University of Colorado Boulder; Dongyang Xu, NovAtel; Yu Jiao, Trimble Navigation; Joanna Hinks, Air Force Research Laboratory
Date/Time: Thursday, Sep. 14, 11:03 a.m.

Peer Reviewed Best Presentation

LEO satellite-based navigation has gained much attention recently. Our earlier simulation study indicated that for signals transmitted from LEO satellites, ionospheric scintillation introduces deeper and more frequent fades and much higher phase dynamics compared to signals transmitted from MEO satellites (Morton et al., 2022). However, there has not been a study on the impact of ionospheric scintillation on the performance of ground-based receiver signal tracking. This paper applies simulated ionospheric plasma irregularity effect on GNSS-like L-band signals transmitted from LEO satellites to assess ground-based receiver signal tracking performance. A physics-based, data-consistent ionosphere scintillation simulator presented by Xu et al. (2020) is used to produce a phase screen model designed to generate realistic strong scintillation effects. The input parameters are extracted from real GPS signal received by a ground station in Hong Kong during a strong ionospheric scintillation event. In this paper, we simulate GPS L1 C/A signals transmitted from LEO orbit, traveling through the phase screen and received by a stationary receiver on the ground. Multiple scenarios have been simulated assuming phase screens generating different levels of scintillation, LEO satellite orbit parameters, and transmission signal parameters such as amplitude and carrier phase. A total of 9 different space-to-time scale factors associated with these satellite and ionosphere phase screen configurations are considered. A conventional receiver architecture is implemented to track the simulated signals. Signal amplitude, carrier phase, and tracking loop performances are analyzed. Both case studies and statistical analysis are presented. The impact of ionospheric plasma irregularities on the signal and its tracking process are analyzed and compared with the same signal traveling through the same irregularity, but from a GPS satellite in MEO orbit. Results show that the same ionospheric structure leads to lower C/N0, less stable tracking loops, more loss-of-lock cases, and more cycle slips for the same signals transmitted from LEO than from MEO. And the negative impact is especially serious with LEO signals having higher phase dynamics, as expected. The statistical analysis of the tracking results provides a quantitative understanding of the level of degradation associated with LEO signal tracking during scintillation. The findings in this study will provide insights into signal design and receiver signal processing strategies for future LEO satellite-based PNT systems.

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