Home

Goddard Space Flight Center, Greenbelt, Maryland 20771

ENGINEERING COLLOQUIUM

Monday, February 7, 2005 / 3:30 PM, Building 3 Auditorium

Judah Levine

"Distributing Time and Frequency Information"

ABSTRACT -- I will begin by discussing how the SI second is defined and how this definition is used to realize International Atomic Time (TAI) and Coordinated Universal Time (UTC). I will then describe how time is transmitted, with emphasis on the general principles that are used to design these distribution systems. I will illustrate these principles using two examples: a method based on messages transmitted over the Internet that can provide time stamps with an uncertainty of about 5 ms, and methods that provide much higher accuracy using the signals from the Global Positioning Satellites. I will conclude with a brief discussion of the leap second problem.

SPEAKER -- Judah Levine is a physicist working in the Time and Frequency Division of NIST. He is also a Fellow of JILA, an institute operated jointly by NIST and the University of Colorado. He received a Ph.D. in physics from New York University in 1966, and has worked in the Time and Frequency Division of NIST (and NBS) since 1972. Dr. Levine's current research work includes studies of the statistics of clocks and oscillators, the design and realization of time scales, and methods for improving the distribution of time and frequency information using the Internet and various satellite systems.




Home