The Long-Term Timing Performance of Satellite Time and Location Receivers Utilizing Signals from Low Earth Orbit Satellites

Peter B. Johnson, Andrew N. Novick

Abstract:	We present the long-term timing accuracy and stability of STL receivers by validating their performance against UTC(NIST), the timing reference at the National Institute of Standards and Technology (NIST), for a duration of 100 days. STL is an existing timing and location service based on signals from Low Earth Orbit (LEO) satellites, available anywhere in the world. The data show that an STL receiver with an oven-controlled crystal (OCXO) or a rubidium (Rb) oscillator provides a stable timing solution and maintains an average offset less than one nanosecond (ns) to UTC(NIST) after calibration. An STL receiver with a Rb oscillator was able to maintain a Maximum Time Interval Error (MTIE) [10] of less than 80 nanoseconds to UTC(NIST) over a period of 66 days, increasing to 90 ns at 100 days duration, meeting the ITU-T G.8272 PRTC-A mask limit of 100 ns. [9] Since the timing variation of these receivers is balanced around an average time offset close the zero, the maximum time offset from UTC(NIST) at any point for the 100 days will be about one half of the MTIE value or less than 50 ns for the STL receiver with a Rb oscillator. The Time Stability (TDEV) of the STL receiver with a rubidium oscillator is less than 9 ns for all values of observation interval tau and the stability (ADEV) is below 2 × 10-13 at one day continuing to average down, reaching below 3 × 10-14 at eight days. All the timing measurements done with these four STL receivers at NIST and a remote lab location were done using Iridiumonly antennas (no GPS band) for the duration of all the testing.
Published in:	Proceedings of the 55th Annual Precise Time and Time Interval Systems and Applications Meeting January 22 - 25, 2024 Hyatt Regency Long Beach Long Beach, California
Pages:	51 - 64
Cite this article:	Johnson, Peter B., Novick, Andrew N., "The Long-Term Timing Performance of Satellite Time and Location Receivers Utilizing Signals from Low Earth Orbit Satellites," Proceedings of the 55th Annual Precise Time and Time Interval Systems and Applications Meeting, Long Beach, California, January 2024, pp. 51-64. https://doi.org/10.33012/2024.19593
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