Geodesy by radio interferometry: Determinations of baseline vector, Earth rotation, and solid earth tide parameters with the Mark I Very Long Baseline Radio Interferometry System

We analyzed 37 very long baseline radio interferometry experiments performed between 1972 and 1978 and derived estimates of baseline vectors between six sites, five in the continental United States and one in Europe. We found no evidence of significant changes in baseline length. For example, with a statistical level of confidence of approximately 85%, upper bounds on such changes within the United States ranged from a low of 10 mm/yr for the 850 km baseline between Westford, Massachusetts, and Green Bank, West Virginia, to a high of 90 mm/yr for the nearly 4000 km baseline between Westford and Goldstone, California. We also obtained estimates for universal time and for the x component of the position of the earth's pole. For the last 15 experiments, the only ones employing wideband receivers, the root-mean-square differences between our values and the corresponding ones published by the Bureau International de l'Heure are 0.0012 s and 0.018 arc sec respectively. The average value we obtained for the radial Love number h for the solid earth is 0.62±0.02 (estimated standard error).