An Analysis and Demonstration of Clock Synchronization by VLBI

Abstract

A prototype of a scmireal-time system for synchronizing the DSN station clocks by radio interferometry was successfully demonstrated on August 30, 1972. The system utilized an approximate maximurn likelihood estimation procedure for processing the data, thereby achieving essentially optimum time synchronization estimates for a given amount of data, or equivalently, minimizing the amount of data required for reliable estimation. Synchronization accuracies as good as 100 nsec rms were achieved bctween DSS 11 and DSS 12, both at Goldstone, California. The accuracy can be improved by increasing the system bandwidth until the fundamental limitations due t o position uncertainties of baseline and source and atmospheric effects are reached. These limitations are under ten nsec for transcontinental baselines.

A review of satellite time transfer technology: Accomplishments and future applications

“…Similarly, very long baseline interferometry (VLBI) can also be used to transfer time once the positions of the baseline stations are accurately determined. Such a series of experiments was recently conducted in the United States and achieved an accuracy of the 10 ns level [Hurd, 1973;Rogers et al, 1977].…”

Instrumental delay calibration for VLBI time comparison via short baseline interferometry

“…The plate tectonics theory was corroborated using this method. It is possible to measure not only the baseline vector but also the relative dif€erence in station time [ 1] [2]. For instrumental &lay calibration, we have developed a short baseline interferometry (SBI) system with a diredly controlled reference hquency.…”