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Measurement of Transient Environmental Effects in GPS-Disciplined Clocks



Andrew Novick, Michael A. Lombardi, Demetrios Matsakis, John Clark


GPS-disciplined clocks (GPSDCs) are designed to optimize the accuracy and stability of their pulse-per-second (PPS) and frequency outputs by steering an internal oscillator to the timing solution from a GPS receiver based on the received satellite signals. The steering function uses either a frequency-lock or phase-locked loop (PLL), typically implemented with a proportional integral derivative (PID) controller. Ideally, a GPSDC will exploit the stability of its local oscillator for short intervals but derive its long-term accuracy and stability from the GPS system's delivered prediction of UTC(USNO), the Coordinated Universal Time (UTC) scale maintained by the United States Naval Observatory (USNO). The output frequency of both quartz and rubidium oscillators is affected by changes in external environmental conditions, primarily temperature. Therefore, it would not be expected that the optimal steering function in the steady state would also be optimal during rapid variations of environmental conditions surrounding the device. We report the observed behavior of several commercially available GPSDCs while they are subjected to rapid temperature variations and discuss potential modifications that might make them less sensitive to these variations.
Proceedings Title
Proceedings of the 54th Precise Time and Time Interval Systems and Applications (PTTI) Meeting
Conference Dates
January 23-26, 2023
Conference Location
Long Beach, CA, US
Conference Title
Precise Time and TIme Interval


GPS, global positioning system, GPS disciplined clock, GPS disciplined oscillator, time calibration, time measurement, environmental effects, temperature


Novick, A. , Lombardi, M. , Matsakis, D. and Clark, J. (2023), Measurement of Transient Environmental Effects in GPS-Disciplined Clocks, Proceedings of the 54th Precise Time and Time Interval Systems and Applications (PTTI) Meeting, Long Beach, CA, US, [online],, (Accessed June 17, 2024)


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Created January 23, 2023, Updated June 7, 2024