The ut1 and utc time services provided by the national institute of standards and technology

Judah Levine

pp. 127-139

in: Elisa Felicitas Arias, Ludwig Combrinck, Pavel Gabor, Catherine Hohenkerk (eds), The science of time 2016, Berlin, Springer, 2017

Abstract

I will describe the network-based time services provided by the Time and Frequency Division of NIST. The network service is realized with approximately 20 servers located at many locations in the USA. The servers receive approximately 340,000 requests per second for time information in a number of different formats. The Network Time Protocol (NTP) receives approximately 98% of these requests. In addition to the servers that transmit UTC time, we also operate a single server that transmits UT1 time in NTP format. The UT1 server implements the offset between UT1 and UTC based on the data in the International Earth Rotation and Reference Systems Service (IERS) Bulletin A. The accuracy of the extrapolation is better than 4 ms; the accuracy of the time received by a user will depend on the stability of the network connection and is generally better than 8 ms. I will also describe the plan to improve the accuracy of the time service. This upgrade should be completed in the next few months.