LEO PNT Frameworks for Non-Cooperative Satellites With Poorly Known Ephemerides: Open-Loop SGP4, Tracking, and Differential

作者：Z. Kassas, Joe Saroufim · 发表于：IEEE Aerospace and Electronic Systems Magazine · 年份：2025 · DOI：10.1109/MAES.2025.3553471 · 被引用次数：10

Four frameworks for low Earth orbit (LEO) positioning, navigation, and timing (PNT) with pseudorange or Doppler measurements from noncooperative satellites with poorly known ephemerides are developed. The first utilizes publicly available ephemerides information from two-line element files, propagated in an open-loop fashion via the simplified general perturbations 4 (SGP4) model. The second utilizes the simultaneous tracking and navigation (STAN) framework, in which the LEO space vehicles' (SVs') position and velocity are simultaneously estimated with the rover's states along with the clock error difference between the rover and LEO SVs. The third is a differential framework, which utilizes measurements made by a base station with a known position. Here, the rover estimates its states along with its clock error difference with that of the base, while the LEO SVs' states are obtained from SGP4. The fourth is differential STAN (DSTAN)—a hybrid of the second and third frameworks. Simulation results are presented comparing frameworks' performance. An aerial vehicle, equipped with a tactical-grade inertial measurement unit (IMU), an altimeter, and global navigation satellite system (GNSS) and LEO receivers, navigates for 28 km, the last 23 km of which are without GNSS signals. The efficacy of the frameworks is compared with various combinations of LEO constellations (Starlink, OneWeb, Iridium NEXT, Orbcomm, and Globalstar), revealing that (1) using more SVs with SGP4 exacerbates ...