Use of Doppler and Doppler Rate for RF Geolocation Using a Single LEO Satellite

Abstract

A passive radio frequency (RF) geolocation solution is provided that uses a single low earth orbit (LEO) satellite to find an uncooperative earth-bound emitter. For the first time, an unambiguous solution is available for real-time, single-pass, and time-constrained acquisition scenarios where single transmissions are expected. The geolocation algorithm rapidly maps Doppler and Doppler rate measurements to an RF emitter location. Corresponding theoretic performance bounds are provided for mission analysis and optimality comparison. The proposed algorithm is a variant of the constrained Unscented Kalman Filter (cUKF), chosen for computational efficiency, modeling abilities, and ease of constraint incorporation. A novel, low-computation method of sigma point projection upon the surface of the earth is derived that drastically improves search area capabilities and convergence rates. The theoretical performance bound is in the form of the recursive constrained Posterior Cramér-Rao Bound (rcPCRB), which is uniquely suited to gauge the mean squared error optimality of iterative nonlinear estimation algorithms. Numerical analysis over measurement noise, center frequency, slant angle, and initialization error exhibit the algorithm's robustness over various mission types. The performance of the cUKF is demonstrated on raw IQ data acquired from the TDS-1 satellite operated by Surrey Satellites.

Improvement of Signal Reception Reliability at Satellite Spectrum Monitoring System

“…Thus, it is easier to apply restrictions to cUKF filters, which are natural when performing the tasks of determining the location of radio emission sources. In [38], the errors in determining the ephemeris and the influence of oscillator drift were considered. However, all the considered works do not take into account the rotation of the Earth, which can affect the accuracy in determining the location of radio emission sources.…”

First results from three years of GNSS interference monitoring from low Earth orbit

“…Assuming a carrier can be extracted from an interference signal, single‐satellite‐based transmitter geolocation is possible from Doppler measurements alone (Becker, 1992; Ellis et al., 2020). The analysis presented here emphasizes the effect of transmitter clock stability on geolocation accuracy.…”

Multi-Constellation Software-Defined Receiver for Doppler Positioning with LEO Satellites

“…The authors in [ 23 ] have shown a new algorithm for estimating the downlink Doppler frequency of LEO satellites as the main measurements of Doppler positioning systems in Nav-SOP applications. Moreover, the analysis of using Doppler and Doppler rate of LEO satellites for Radio Frequency (RF) geolocation and enhancement of Doppler positioning algorithms for stand-off trajectories are studied in [ 24 , 25 ], respectively. A Precise Point Positioning (PPP) system was also designed and validated in [ 26 , 27 ].…”