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Search Publications by: Judah Levine (Fed)

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Displaying 1 - 25 of 111

A Resilient Architecture for the Realization and Distribution of Coordinated Universal Time to Critical Infrastructure Systems in the United States: Methodologies and Recommendations from the National Institute of Standards and Technology (NIST)

November 3, 2021
Author(s)
Jeffrey Sherman, Ladan Arissian, Roger Brown, Matthew J. Deutch, Elizabeth Donley, Vladislav Gerginov, Judah Levine, Glenn Nelson, Andrew Novick, Bijunath Patla, Tom Parker, Benjamin Stuhl, Jian Yao, William Yates, Michael A. Lombardi, Victor Zhang, Douglas Sutton
The Time and Frequency Division of the National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce (DOC), was tasked with fulfilling Section 4, Part (i) of the Position, Navigation and Timing (PNT) Executive

Distributing Time and Frequency Information

December 15, 2020
Author(s)
Judah Levine
This chapter discusses the statistics that are used to characterize the performance of clocks, oscillators, and the networks that are used to calibrate and synchronize and calibrate clocks and oscillators by means of data received from global navigation

Optical-Clock-Based Time Scale

October 30, 2019
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Andrew D. Ludlow, Holly Leopardi, Thomas E. Parker, William F. McGrew, Scott A. Diddams, Judah Levine
A time scale is a procedure for accurately and continuously marking the passage of time. It is exemplified by coordinated universal time (UTC), and provides the backbone for critical navigation tools such as the global positioning system (GPS). Present

Metrological and legal traceability of time signals

March 1, 2019
Author(s)
Michael A. Lombardi, Demetrios Matsakis, Judah Levine
Metrological traceability requires an unbroken chain of calibrations that relate to a reference, with each calibration having a documented measurement uncertainty. In the field of time and frequency metrology, the desired reference is usually Coordinated

Progress on Optical-clock-based Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

April 20, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

Incorporating an Optical Clock into a Time Scale at NIST: Simulations and Preliminary Real-Data Analysis

March 29, 2018
Author(s)
Jian Yao, Jeffrey A. Sherman, Tara M. Fortier, Thomas E. Parker, Judah Levine, Joshua J. Savory, Stefania Romisch, William F. McGrew, Robert J. Fasano, Stefan A. Schaeffer, Kyle P. Beloy, Andrew D. Ludlow
This paper shows the recent NIST work on incorporating an optical clock into a time scale. We simulate a time scale composed of continuously-operating commercial hydrogen masers and an optical frequency standard that does not operate continuously as a

Metrological and legal traceability of time signals

January 30, 2018
Author(s)
Demetrios Matsakis, Judah Levine, Michael A. Lombardi
Metrological traceability requires an unbroken chain of calibrations that relate to a reference, with each calibration having a documented measurement uncertainty. In the field of time and frequency metrology, the desired reference is usually Coordinated

Incorporating an Optical Clock into a Time Scale

January 1, 2018
Author(s)
Jian Yao, Thomas E. Parker, Neil Ashby, Judah Levine
This paper discusses how to build a time scale with an intermittently-operated optical clock. In particular, it gives suggestions on how long and how often to run an optical clock. It also explores the benefits of having an optical clock in a time scale

JY1 Time Scale: a New Kalman-Filter Time Scale Designed at NIST

October 17, 2017
Author(s)
Jian Yao, Thomas E. Parker, Judah Levine
We report on a new Kalman-filter Hydrogen-maser time scale (i.e., JY1 time scale) designed at NIST. The JY1 time scale is composed of a few Hydrogen masers and a Cs clock. The Cs clock is used as a reference clock, to ease operations with existing data

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

GPS Measurements Anomaly and Continuous GPS Carrier-Phase Time Transfer

December 4, 2014
Author(s)
Jian Yao, Judah Levine
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 a lot and can be solved by a few