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Search Publications by: Michael A. Lombardi (Assoc)

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Displaying 51 - 75 of 287

Improvements in SIM Time Network and SIM Time Scale Performance

October 10, 2014
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz, E. de Carlos-Lopez, Marina Gertsvolf, Ricardo de Carvalho
We report recent results achieved within the Sistema Interamericano de Metrología (SIM) regarding the multinational cooperation program in the field of time and frequency metrology. We discuss the performance of the SIM Time Network (SIMTN) and the SIM

WWVB: A Half Century of Delivering Accurate Frequency and Time by Radio

March 12, 2014
Author(s)
Michael A. Lombardi, Glenn K. Nelson
In commemoration of its 50th anniversary of broadcasting from Fort Collins, Colorado, this paper provides a history of National Institute of Standards and Technology (NIST) radio station WWVB. The narrative describes the evolution of the station, from its

Frequency Measurement

February 3, 2014
Author(s)
Michael A. Lombardi
An overview of frequency metrology, with emphasis on estimating accuracy and stability, oscillator types, and measurement instrumentation. It describes how to measure frequency and the statistics and terminology that are used to report the results. The

Time Measurement

February 3, 2014
Author(s)
Michael A. Lombardi
An overview of time metrology, with emphasis on time interval measurements, and time synchronization. It covers the evolution of clocks and timekeeping, time scales, the fundamentals of time measurement, and the various time transfer technique used to

Automated Control of National Time Standards via the SIM Time Scale

September 27, 2013
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz
This paper describes a frequency and time control system developed by the Sistema Interamericano de Metrologia (SIM). Due to limited resources, some SIM national metrology institutes maintain a low-cost rubidium clock as their national time standard

The SIM time scale

April 20, 2013
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz, E. de Carlos-Lopez
Time measurement is of great importance for science, technology and commerce. Among the seven base units of the International System (SI), the second can be realized with the smallest uncertainty, currently reaching parts in 10 16. Keeping track of the

Replicating UTC(NIST) at Remote Sites

November 26, 2012
Author(s)
Michael A. Lombardi, Andrew N. Novick, J. Mauricio Lopez-Romero, Rodrigo Ramos
The National Institute of Standards and Technology (NIST) is deploying disciplined oscillators that are referenced to the UTC(NIST) time scale through common-view observations of Global Positioning System (GPS) satellites. We present measurement results

The Need for a Robust, Precise Time and Frequency Alternative to GNSS

November 1, 2012
Author(s)
Michael A. Lombardi, Mitch Narins, Per Enge, Ben Peterson, Sherman Lo, Yu-Hsuan Chen, Dennis Akos
Positioning, Navigation, and Timing (PNT) services are key enablers of both essential safety and security applications and economically beneficial capacity and efficiency applications worldwide. Whether users are ground-based, sea-based or in the air

Microsecond Accuracy at Multiple Locations: Is it possible without GPS?

October 1, 2012
Author(s)
Michael A. Lombardi
The microsecond is the most discussed unit in industrial timing systems, because microsecond accuracy is required to support critical infrastructure. Most critical infrastructure timing systems depend upon GPS, simply because microsecond accuracy is easy

International time and frequency comparisons in real time: recent results

July 2, 2012
Author(s)
Michael A. Lombardi, J. Mauricio Lopez-Romero, Nelida Diaz-Munoz, Eduardo de Carlos Lopez
Within the Sistema Interamericano de Metrologia (SIM) region, a time comparison network, SIMTN, has been developed. The SIMTN continuously compares the time scales of SIM members and publishes measurement results in near real-time. The measurements are