Local Distribution and Calibration of Timing Signals at NIST

Published

January 31, 2017

Author(s)

Joshua J. Savory, Liz C. Forero, Kristopher Maurer, Stefania Romisch

Abstract

The National Institute of Standards and Technology (NIST) timescale produces a real-time realization of UTC(NIST) in the form of a pulse-per-second (PPS) time signal and a 5 MHz frequency reference. The timing signals are distributed to the international and domestic community using various time transfer links (Two-Way Satellite Time and Frequency Transfer (TWSTFT), Global Positioning System (GPS), Network Time Protocol (NTP), NIST Automated Computer Time Service (ACTS), and NIST Time Measurement and Analysis Service (TMAS)). Accurate distribution of the NIST PPS time signal is dependent upon calibration of the time delay introduced by each link with respect to the UTC(NIST) reference point. Hardware constraints, spatial constraints and in some cases simply convenience require that the physical input to these links be distributed throughout the NIST campus. A robust on-campus timing distribution and calibration system is required to ensure the accuracy and stability of the signals received at each link. The current error budget for a typical link calibration requires local delays to be known to an uncertainty of less than ~200 ps. We utilize a clock trip calibration protocol to measure the delays introduced by local time distribution system at NIST. A clock trip involves measuring the time difference between the UTC(NIST) reference point and a travelling clock, then transporting the travelling clock to a remote secondary reference point followed by a subsequent measurement of the time difference at the remote location. Clock trips are advantageous as they are a nonintrusive measurement of the full system delay. To achieve calibrations with an accuracy on the order 100 ps, we have developed a means to transport a cesium clock between remote locations on site with minimal vibration and an analysis protocol to maximize the information acquired by each clock trip. We will introduce the system used to distribute time signals at NIST, the hardware and protocol we have dev

Conference Dates

January 30-February 2, 2017

Conference Location

Monterey, CA

Conference Title

Proceedings of the 2017 ION Precise Time and Time Interval Meeting (PTTI)

Pub Type

Conferences

Keywords

Calibration, Clock Trip, Time, UTC

Citation

Savory, J. , Forero, L. , Maurer, K. and Romisch, S. (2017), Local Distribution and Calibration of Timing Signals at NIST, Proceedings of the 2017 ION Precise Time and Time Interval Meeting (PTTI), Monterey, CA (Accessed May 2, 2024)