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Search Publications by: Judah Levine (Fed)

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Displaying 26 - 50 of 224

The development of a new Kalman-filter time scale at NIST

January 31, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a preliminary design of a new Kalman-filter Hydrogen-maser time scale at NIST. The time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, just for easy operations with the existing data. All

Coordinated Universal Time and the Leap Second

December 1, 2016
Author(s)
Judah Levine
I will discuss the considerations that were important in the design of the current version of Coordinated Universal Time. The design includes the addition of additional “leap” seconds to keep Coordinated Universal time within 0.9 s of the UT1 time scale

Measuring Time and Comparing Clocks

April 1, 2016
Author(s)
Judah Levine
I will discuss methods of comparing and synchronizing clocks and the procedure of characterizing their performance in terms of the two-sample Allan variance. I will describe methods that are used when the device under test and the reference device are in

Usage analysis of a national internet time service

March 8, 2016
Author(s)
Jeffrey A. Sherman, Judah Levine
The Internet Time Service (ITS) at the National Institute of Standards and Technology (NIST) currently receives over 12 billion time requests per day. ITS servers derive their system time from the NIST atomic-referenced timescale and distribute it freely

GPS Jamming and GPS Carrier-Phase Time Transfer

January 25, 2016
Author(s)
Jian Yao, Marc A. Weiss, Charles Curry, Judah Levine
This paper studies the impact of GPS jamming on GPS carrier-phase time transfer. To study this issue, at NIST, we have installed a commercial GPS jamming detector since 2014 April. During 2014 April – 2015 April, the detector detected more than 100 jamming

A detailed comparison of two continuous GPS carrier-phase time transfer techniques

September 8, 2015
Author(s)
Jian Yao, Judah Levine, Skakun Ivan, Zhiheng Jiang
The wide application of GPS carrier-phase (CP) time transfer is limited by the problem of boundary discontinuity (BD). The discontinuity has two categories. One is "day boundary discontinuity," which has been studied extensively and can be solved by a few

Comparison of Two Continuous GPS Carrier-Phase Time Transfer Techniques

April 12, 2015
Author(s)
Jian Yao, Skakun Ivan, Zhiheng Jiang, Judah Levine
Global Positioning System (GPS) carrier-phase (CP) time transfer, as a widely accepted high-precision time transfer method, frequently shows a data-batch boundary discontinuity of up to 1 ns, because of the inconsistency of the phase ambiguities between