Austin M. Smith and David M. Bevly, Auburn University

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The work presented in this paper aims to assess the accuracy, stability, and convergence rates of static receiver timing solutions from low-Earth orbit (LEO) Satellite Time and Location (STL) signals. The motivation for this work lies in the wide range of industries that rely on nanosecond-level timing precision. Traditional means of satellite-based timing, such as Global Navigation Satellite Systems (GNSS), prove to be vulnerable under various conditions, compromising their accuracy. The STL signals from the Iridium satellite constellation are received at a much higher signal power, rendering them more resilient to these interferences. Two tests were conducted in this study. For Test 1, two scenarios were considered. The first scenario assumes a known, static antenna position, where the receiver clock bias and drift were estimated with an Extended Kalman Filter (EKF). The second scenario assumes an unknown, static antenna position, where a 3-dimensional Earth-Centered, Earth-Fixed (ECEF) position, clock bias and clock drift were estimated with a Recursive Least Squares (RLS) Solution. The algorithms were implemented with live-sky STL data collected with a newly-released, commercially-available Jackson Labs STL-2600 receiver with a Rubidium clock input. For Test 2, a time interval difference test between the Jackson Labs receiver 1-PPS output and a GNSS 1-PPS reference. In each of the tests, the long-term timing accuracy was determined to be within 205 nanoseconds, with sub-nanosecond per second drift. The results for Test 1 include time state estimate plots, filter covariance convergence, and error statistics. The results for Test 2 include pre- and post-settling time difference plots and error statistics.