U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by:

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 1 - 25 of 43

Use of SDR Receivers in TWSTFT for UTC Computation

August 3, 2018
Author(s)
Zhiheng Jiang, Victor S. Zhang, Yi-Jiun Huang, Joseph Achkar, Dirk Piester, Shinn-Yan Lin, Wenjun Wu, Sung-hoon Yang, Jerzy Nawrocki, Ilaria Sesia, Christian Schlunegger, Zhiqiang Yang, Miho Fujieda, Albin Czubla, Hector Esteban, Carsten Rieck, Peter Whibberley
Two-Way Satellite Time and Frequency Transfer (TWSTFT) is a primary technique for the generation of Coordinated Universal Time (UTC). About 20 timing laboratories around the world continuously operate TWSTFT using the SAtellite Time and Ranging Equipment

Implementation of SDR TWSTFT in UTC Computation

January 30, 2018
Author(s)
Zhiheng Jiang, Felicitas Arias, Victor S. Zhang, Yi-Jiun Huang, Joseph Ackhar, Dirk Piester, Shinn-Yan Lin, Wenjun Wu, Andrey Naumov, Sung-hoon Yang, Jerzy Nawrocki, Ilaria Sesia, Christian Schlunegger, Kun Liang
Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW for short) is a primary technique for the realization of Coordinated Universal Time (UTC), which is computed by the International Bureau of Weights and Measures (BIPM). TWSTFT is carried out

A Study on Using the SDR Receiver for the Europe-Europe and Transatlantic TWSTFT Links

January 31, 2017
Author(s)
Victor S. Zhang, Thomas E. Parker, Joseph Achkar, Dirk Piester, Yi-Jiun Huang, Shinn-Yan Lin, Zhiheng Jiang
The BIPM and the CCTF Working Group on TWSTFT have stimulated a pilot study on using software defined radio (SDR) receivers for TWSTFT in the framework of the realization of International Atomic Time (TAI). The SDR receivers based on a software developed

Accurate TWSTFT time transfer with indirect links

January 31, 2017
Author(s)
Victor S. Zhang, Zhiheng Jiang, Thomas E. Parker, Jian Yao, Yi-Jiun Huang, Shinn-Yan Lin
The conventional wisdom suggests a direct Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) time link should result in a smaller uncertainty than that of an indirect TW link over the same baseline [12]. This is why all Coordinated Universal Time

Long-term instability in UTC time links

January 31, 2017
Author(s)
Victor S. Zhang, Demetrios Matsakis, Zhiheng Jiang
Calibration and link stability are the key issues for the UTC time transfer. This study is made in the framework of a joint task group of the CCTF Working Group on TWSTFT and Working Group on GNSS Time Transfer to investigate the long-term instability of

The effects of the January 2016 UTC offset anomaly on GPS clocks monitored at NIST

January 31, 2017
Author(s)
Jian Yao, Michael A. Lombardi, Andrew N. Novick, Bijunath Patla, Jeffrey A. Sherman, Victor S. Zhang
Errors in the Coordinated Universal Time (UTC) offset parameters broadcast by Global Positioning System (GPS) satellites caused many thousands of GPS clocks to be in error by approximately -13 µs on January 25-26, 2016. The erroneous UTC offset information

Doppler Sensitivity and Its Effect on Transatlantic TWSTFT Links

December 6, 2016
Author(s)
Shengkang Zhang, Tom Parker, Victor S. Zhang
Two Way Satellite Time and Frequency Transfer (TWSTFT or TW) is a commonly used technique to compare time and frequency precisely among the time and frequency laboratories. The precision of TWSTFT on time comparison is about 0.5 ns or even better, which

A Study on Reducing the Diurnal in the Europe-to-Europe TWSTFT Links.

April 4, 2016
Author(s)
Victor S. Zhang, Thomas E. Parker, Shengkang Zhang
Most of the Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) links exhibit a daily variation (diurnal) on the order of 1 ns in the differences. The stability of TW is degraded by the diurnal. Many studies on the sources of diurnal have been

The 2015 TWSTFT calibration for UTC and related time links

April 4, 2016
Author(s)
Zhiheng Jiang, Dirk Piester, Christian Schlunegger, Erik Dierks, Javier Galindo, Demetrios Matsakis, Victor S. Zhang
Two-Way Satellite Time and Frequency Transfer (TWSTFT or TW) is one of the primary time transfer techniques for UTC generation. Although it has expensive financial requirements it provides highly accurate calibration, and provides both robustness and

Precision measurement of the speed of propagation of neutrinos using the MINOS detectors

September 17, 2015
Author(s)
Stefania Romisch, P Adamson, I Anghel, Neil Ashby, A Aurisano, G. Barr, M. Bishai, A. Blake, C. M. Castromonte, S. Childress, M. Christensen, J. A. Coelho, L. Corwin, D. Cronin-Hennessy, J. K. de Jong, A. V. Devan, N. E. Devenish, M. V. Diwan, C. O. Escobar, J. J. Evans, E. Falk, G. J. Feldman, Blair Fonville, M. V. Frohne, H. R. Gallagher, R. A. Gomes, M. C. Goodman, P. Gouffon, N. Graf, R. Gran, K. Grzelak, A. Habig, S. R. Hahn, J. Hartnell, R. Hatcher, Jonathan Hirschauer, A. Holin, J. Huang, J. Hylen, G M. Irwin, Z. isvan, C. James, Steven R. Jefferts, D. Jensen, T. Kafka, S. M. Kasahara, G. Koizumi, M. Kordosky, A. Kreymer, K. Lang, J. Ling, P. J. Litchfield, P. Lucas, W. A. Mann, M. L. Marshak, Demetrios Matsakis, N. Mayer, Angela Mckinley, C. McGivern, M. M. Medeiros, R. Mehdiyev, J Meier, M. D. Messier, W. H. Miller, S. R. Mishra, Stephen Mitchell, S. Moed Sher, C. D. Moore, L. Mualem, J. A. Musser, D. Naples, J. K. Nelson, H. Newman, R. J. Nichol, J. A. Nowak, J. C. O'Conner, M. Orchanian, R. B. Pahlka, J. Paley, Thomas E. Parker, R. B. Patterson, G. Pawloski, A. Perch, S. Phan-Budd, R. K. Plunkett, N. Poonthattatil, Ed Powers, X. Qiu, A. Radovick, B. Rebel, K. Ridl, C. Rosenfeld, H. A. Rubin, M. C. Sanchez, J. Schneps, A. Schreckenberger, P. Schreiner, R. Sharma, A, Sousa, N. Tagg, R, L. Talaga, J. Thomas, M. A. Thomson, X. Tian, A. Timmons, S. C. Tognini, R. Toner, D. Torretta, J. Urheim, P. Vahle, B. Viren, A. Weber, R. C. Webb, C. White, L. Whitehead, L. H. Whitehead, S. G. Wojcicki, J. Wright, Victor S. Zhang, R. Zwaska
We report a two-detector measurement of the propagation speed of neutrinos over a baseline of 734 km. The measurement was made with the NuMI beam at Fermilab between the near and far MINOS detectors. The fractional difference between the neutrino speed and

Long-Term Uncertainty in Time Transfer Using GPS and TWTFT Techniques

April 13, 2015
Author(s)
Victor S. Zhang, Thomas E. Parker, Jian Yao
The techniques of GPS time and frequency transfer (code based and carrier phase) and two-way satellite time and frequency transfer (TWSTFT) are widely used in remote clock comparison and in the computation of International Atomic Time (TAI). Many timing

Measured Ionosphere Delay Correction for Code-Based GPS Time Transfer

December 4, 2014
Author(s)
Victor S. Zhang, Zhiqi Li
Nowadays, more and more dual-frequency, multichannel receivers are used in GPS time and frequency transfer applications. Instead of using the modeled ionosphere delay correction or using the IGS ionospheric map, we can obtain the ionosphere delay

A Low-Cost Time Transfer Receiver for Contributions to Coordinated Universal Time

November 6, 2014
Author(s)
Michael A. Lombardi, Andrew N. Novick, Victor S. Zhang
This paper describes a low-cost time transfer receiver that allows timing laboratories, including national metrology institutes and other designated institutions, to contribute data to the computation of Coordinated Universal Time (UTC). The time transfer

A Study of the Diurnal in the Transatlantic TWSTFT Difference

September 7, 2013
Author(s)
Victor S. Zhang, Thomas E. Parker
The daily variation (diurnal) in the two-way satellite time and frequency transfer (TWSTFT) difference is one of the most significant instabilities of the TWSTFT technique. The diurnal comes from the daily delay change of the TWSTFT signal paths. In recent

Enabling accurate differential calibration of modern GPS receivers

November 26, 2012
Author(s)
Stefania Romisch, Victor S. Zhang, Thomas E. Parker, Steven R. Jefferts
The difference between the local time reference and a GNSS receiver's internal time base is an essential contributor to the calibration of that receiver when used as a timing device. In the past, in the absence of a PPS output signal provided by the

Measurement of the velocity of the neutrino with MINOS

November 26, 2012
Author(s)
Stefania Romisch, P Adamson, Neil Ashby, G. Barr, M. Bishal, A. Blake, G. J. Bock, D. Bogert, Russell Bumgarner, S. V. Cao, S. Childress, M. Christensen, J. Coelho, L. Corwin, D. Cronin-Hennessy, J. K. de Jong, N. E. Devenish, M. V. Diwan, C. O. Escobar, J. J. Evans, E. Falk, G. J. Feldman, C. Flores, Blair Fonville, M. V. Frohne, H. R. Gallager, A. Gavrilenko, R. A. Gomes, P. Gouffon, N. Graf, R. Gran, K. Grzelak, A. Habig, J. Hartnell, R. Hatcher, Jonathan Hirschauer, A. Holin, J. Hylen, G M. Irwin, Z. isvan, C. James, Steven R. Jefferts, D. Jensen, T. Kafka, S. M. Kasahara, G. Koizumi, M. Kordosky, A. Kreymer, K. Lang, J. Ling, P. J. Litchfield, P. Lucas, W. A. Mann, M. L. Marshak, M. Mathis, Demetrios Matsakis, N. Mayer, Angela Mckinley, M. M. Medeiros, R. Mehdiyev, J. R. Meier, B. Mercurio, M. D. Messier, W. H. Miller, S. R. Mishra, S. Moed Sher, C. D. Moore, L. Mualem, J. A. Musser, J. K. Nelson, H. Newman, R. J. Nichol, J. A. Nowak, J. C. O'Conner, W. P. Oliver, M. Orchanian, R. B. Pahlka, J. Paley, Thomas E. Parker, R. B. Patterson, G. Pawloski, S. PhanBudd, R. K. Plunkett, N. Poonthattatil, Ed Powers, X. Qiu, A. Radovic, B. Rebel, C. Rosenfeld, H. A. Rubin, M. C. Sanchez, J. Schneps, P Schireiner, A. Schreckenberger, R. Sharma, A, Sousa, N. Tagg, R, L. Talaga, J. Thomas, M. A. Thomson, X. Tian, S. C. Tognini, R. Toner, D. Torretta, G. Tzanakos, J. Urheim, P. Vahel, A. Webber, R. C. Webb, C. White, L. H. Whitehead, L. Whitehead, K. P. Wilson, S. G. Wojcicki, J. Wright, Victor S. Zhang, R. Zwaska
The MINOS experiment uses a beam of predominantly muon-type neutrinos generated using protons from the Main Injector at Fermilab in Batavia, IL and travelling 735 km through the Earth to a disused iron mine in Soudan, MN. The 10 us-long beam pulse contains

Recent Calibrations of UTC(NIST) and UTC(USNO)

November 26, 2012
Author(s)
Victor S. Zhang, Thomas E. Parker, Russell Bumgarner, Jonathan Hirschauer, Angela Mckinley, Stephen Mitchell, Ed Powers, Jim Skinner, Demetrios Matsakis
The National Institute of Standards and Technology (NIST) and the United States Naval Observatory (USNO) use GPS common-view, carrier-phase time transfer and Two Way Satellite Time and Frequency Transfer (TWSTFT, also known as TWSTT) techniques in our time

Synchronization between remote sites for the MINOS experiment

November 26, 2012
Author(s)
Stefania Romisch, Steven R. Jefferts, Victor S. Zhang, Thomas E. Parker, Neil Ashby, P Adamson, G. Barr, A. Habig, J Meier, C. James, R. Nicol, R. Plunkett, C. Rosenfeld, Russell Bumgarner, M. Christensen, Jonathan Hirschauer, Blair Fonville, Demetrios Matsakis, Ed Powers, J. Wright, Angela Mckinley
In the context of time-of-flight measurements, the timing at the departure and arrival locations is obviously critical to the outcome of the experiment. In the case of neutrino time-of-flight experiments, the locations are many hundreds of kilometers apart

Coordinating GPS Calibrations Among NIST, NRL, USNO, PTB, and OP

July 31, 2011
Author(s)
Marc A. Weiss, Victor S. Zhang, J White, K Senior, Demetrios Matsakis, S. Mitchell, P Uhrich, D Valat, W Lewandowski, G. Petit, Andreas Bauch, T. Feldman, A. Proia
Reviewing calibration results over the history since early 1980’s among several labs shows very mixed results. The best stabilities of receivers, as given by calibrations, are of the order of a few ns or better over a year, though many results are quite a

Distributing UTC(NIST) to Industrial Time and Frequency Users

November 18, 2009
Author(s)
Michael A. Lombardi, Victor S. Zhang
The National Institute of Standards and Technology (NIST) maintains one of the world s most accurate and stable time scales, UTC(NIST), as well as the NIST-F1 cesium fountain, the primary frequency standard for the United States. These standards are

Two-Way Satellite Time and Frequency Transfer Using 1 MChip/S codes

November 16, 2009
Author(s)
Victor S. Zhang, Thomas E. Parker, Demetrios Matsakis, Joseph Achkar, Daniele Rovera, Dirk Piester, Andreas Bauch, Luca Lorini
The Ku-band transatlantic and Europe to Europe two-way satellite time and frequency transfer (TWSTFT) operations used the 2.5 MChip/s pseudo-random codes with 3.5 MHz bandwidth until the end of July, 2009. The cost of TWSTFT operation is associated with