Remote Time Calibrations via the NIST Time Measurement and Analysis Service

The National Institute of Standards and Technology (NIST) now offers a new remote calibration service designed to assist laboratories that maintain an accurate local time standard. The service monitors the local time standard by continuously comparing it to the national time standard and reports the comparison results to the customer in near real-time. This new service, called the NIST Time Measurement and Analysis Service, or TMAS, works by making simultaneous common-view measurements at NIST and at the customer’s laboratory with up to eight Global Positioning System (GPS) satellites. Each customer receives a time measurement system that performs the measurements and sends the results to NIST via the Internet for instant processing. Customers can then view their standard’s performance with respect to NIST in near real-time, using an ordinary web browser. Time is measured with a combined standard uncertainty of less than 15 nanoseconds, and frequency is measured with an uncertainty of less than 1#10–13 after 1 day of averaging. This paper describes the multi–channel GPS common–view technique used by the service and the measurement system sent to each customer. It also explains how NIST calibrates each measurement system prior to shipment, how measurement results are reported to the customer, and how the measurement uncertainties are estimated. 1 This paper is a contribution of the United States government, and is not subject to copyright. An earlier version of this paper appeared in the 2006 NCSLI Conference proceedings. The identification of commercial equipment is for purposes of illustration only, and does not imply endorsement by NIST or by NCSL International. Michael A. Lombardi and Andrew N. Novick Time and Frequency Division National Institute of Standards and Technology1 Boulder, CO 80305 USA Email: [email protected]