Radio interferometry techniques for geodesy

The Project ARIES g-meter transportable antenna has been used as one element of a very long baseline interferometer (VLBI) to begin monitoring locations of six sites in California relative to large diameter fixed antennas at the NASA Deep Space Network, Goldstone, California, and at the Caltech Owens Valley Radio Observatory, Big Pine, California. An accuracy of about 6 cm in the horizontal components has been demonstrated by comparison with measurements of the National Geodetic Survey. The RMS scatter of the lengths of the baselines between any pair of antennas is about 3 cm except for the Goldstone-JPL (Pasadena) baseline. In the period August 1974 to August 1977 the length of this baseline increased by 15 f 5 cm as JPL moved westward relative to Goldstone at the rate of 6 * 2 cm/year. The baseline lengths are unaffected by the uncertainties of UTl, polar motion, and tropospheric water vapor, which are the limitations to present three-dimensional vector accuracies. Initial demonstrations have been made with a highly mobile 3.7-m-diameter antenna, but marginal system sensitivity has limited the accuracy. Planned improvements such as a low-noise receiver and wide-band Mark III data system will provide baseline precisions of a few centimeters for about two sites per week beginning about summer 1981. *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. 3 4 RADIO INTERFEROMETRY ANALYSIS E. S. Claflin T. E. Erickson H. F. Fliegel A. Y. Lam T. G. Lockhart P. F. M R. B. N A. E. Ni K. M. Ong G. M. R J. S. Spitler C. J. Steinberg K. S. Wallace i ITI ell