TWSTFT: It's History, Evolution and People

William Klepczynski

Abstract:	As timing capabilities in laboratories improve, the techniques we use to compare and evaluate clocks over large distances must also improve. Today, I would like to talk about the factor that has been behind the continual improvement of the Two Way Satellite Time and Frequency Transfer (TWSTFT) technique over the last 50 years. The way a technique improves, is to seek improvement in its PRECISION and ACCURACY. Lewandowski (2013) [1] has listed the present day estimates for the precision (Type A error (uA)) and accuracy (Type B error (uB)) [2] of Two Way as 200 ps and 1 ns, respectively. Fifty years (1964) ago, timekeeping capabilities (clocks and time scales) at the major laboratories of the world were between 25-100 rnicrosecond levels. Forty years ago, they were at the 5-25 rnicrosecond level. Thirty years ago, 1 rnicrosecond timekeeping was being routinely kept in many laboratories. In fact, the major timekeeping centers were keeping sub-microsecond level timing, in the 5-200 nanosecond range. Today’s clocks are keeping time at picosecond levels.
Published in:	Proceedings of the 46th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 4, 2014 Seaport Boston Hotel Boston, Massachusetts
Pages:	1 - 4
Cite this article:	Klepczynski, William, "TWSTFT: It's History, Evolution and People," Proceedings of the 46th Annual Precise Time and Time Interval Systems and Applications Meeting, Boston, Massachusetts, December 2014, pp. 1-4.
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