U.S.-Japan Cooperative Research: Study of the Earth's Variable Rotation, and Terrestrial and Celestial Reference Frames Based on Japan-U.S. Cooperative VLBI Observations

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This award will enable Dr. William E. Carter, of the Geodetic Research and Development Laboratory of the U.S. National Geodetic Survey, and his research group, to collaborate with Dr. Koichi Yokoyama and co-workers of the International Latitude Observatory of Mizusawa, Japan, over a period of two years. They will work on problems related to the interconnection of the North America and Europe Very Long Baseline Interferometry (VLBI) network with the Japan and North America VLBI network. Software used by the two systems will be rationalized, joint test observing sessions will be conducted, and special observing sessions will be conducted to ascertain optimum sampling frequencies. The purpose of this research is to facilitate the interconnection of these continent-scale VLBI networks, thus greatly enhancing the precision of geodetic measurements. VLBI, in which simultaneous observations taken by widely-spaced radio telescopes can be correlated to achieve angular precision under a millisecond of arc and terrestrial distance references to within a centimeter, is the most powerful method of monitoring variations in the earth's polar motion, precession, and nutation. Observations will be taken by both the U.S. and Japanese teams on their respective VLBI networks, and the raw data will be processed by the U.S. team. The results will be presented in joint research papers.