Demonstration of Remote Clock Monitoring by VLBI, With Three Baseline Closure

C.M. Cheetham, W.J. Hurd, J.W. Layland

Abstract:	The capability of very long baseline Interferometry (VLBI) to monitor the stability of remotely-located hydrogen maser frequency standards has been demonstrated by a series of experiments conducted from September 1978, through January 1979, between Deep Space Stations in Australia, Spain, and California. The measured stabilities of the clock systems, over approximately 10-day intervals, were 1 to 3 parts in 101), with the instabilities due to the oscillators, the clock distribution systems, the receiving system delays, and the VLBI measurement error. Experiments were conducted independently using two different systems (BLOCK 0 and WBDAS). Later comparison shows agreement on the order of 1 part in 1013. Closure was demonstrated on three separate occasions to 33, 10, and 13 ns with an error uncertainty of +42 ns. The results represent an important consistency check on VLBI measurements. This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.
Published in:	Proceedings of the 11th Annual Precise Time and Time Interval Systems and Applications Meeting November 27 - 29, 1979 Goddard Space Flight Center Greenbelt, Maryland
Pages:	557 - 578
Cite this article:	Cheetham, C.M., Hurd, W.J., Layland, J.W., "Demonstration of Remote Clock Monitoring by VLBI, With Three Baseline Closure," Proceedings of the 11th Annual Precise Time and Time Interval Systems and Applications Meeting, Greenbelt, Maryland, November 1979, pp. 557-578.
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