Joint pseudo-range and Doppler positioning method with LEO Satellites‘ signals of opportunity

Abstract Low Earth Orbit (LEO) satellites, with their wide coverage and large number, have gradually become a crucial platform and means for navigation and positioning services. Compared to other LEO constellations, Starlink has over 6000 satellites in orbit, and its signals contain synchronous sequences usable for pseudo-range positioning. Thus, it has a potential serve as an alternative to Global Navigation Satellite System (GNSS) for providing Positioning, Navigation, and Timing (PNT) services. Compared to parabolic antennas and electronically scanned phased array antennas for receiving Starlink signals, wide-beam antennas (such as Low-Noise Block (LNB) downconverters) can be used to achieve low-cost multi-satellite tracking. However, it also encounters the issues of distinguishing between multiple satellite signals and low received signal power, which requires high-sensitivity detection. Moreover, there are some other issues such as unknown signal transmission time and real-time satellite orbits, thereby causing failure to navigation. Accordingly, this study focuses on LEO constellations represented by Starlink, proposes a joint pseudo-range and Doppler positioning method for Starlink satellite Signals of Opportunity (SOP) based on the comprehensive utilization of signals and information from LEO satellites. Moreover, this study analyzes the signal detection capability and satellite isolation method, examines the algorithm’s orbital error suppression performance, and establishes the concept of Equivalent Position Dilution of Precision (EPDOP) $$s_{{{\text{EPDOP}}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>s</mml:mi> <mml:mtext>EPDOP</mml:mtext> </mml:msub> </mml:math> for joint pseudo-range and Doppler positioning. In the experiment because Starlink satellite signals are not available in China, we take the advantage of Iridium NEXT satellites’ global seamless coverage, utilize an algorithm to get pseudo-range observations with the Iridium NEXT signals, and then combine them with Starlink Doppler observations to achieve the joint pseudo-range and Doppler positioning of LEO satellites’ SOPs. The experiment results demonstrate that when relying on Starlink Doppler observations for positioning, the proposed method achieves Two-Dimensional (2D) positioning accuracy of 3.6 m and Three-Dimensional (3D) positioning accuracy of 6.2 m. Compared to existing Starlink positioning algorithms based on parabolic antennas and electronically scanned phased array antennas, this method improves the accuracy by at least 35.7%. Additionally, Iridium NEXT signals are used to validate the performance of the proposed algorithm for joint pseudo-range and Doppler positioning. In a 40 km long-baseline scenario, the algorithm achieved a 2D positioning accuracy of 24 m and a 3D positioning accuracy of 41 m with Iridium NEXT satellite pseudo-range and Doppler measurements.