PRECISE DOMESTIC VLBI IN 22GHz BAND FOR GEODESY

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VLBI in 22GHz band is a powerful technique for geodesy because of wide bandwidth, small propagation delay, possibility of the correction for tropospheric delay and small size of a radio source. However, there are some dificulties to realize VLBI in 22GHz band for geodesy such as a small number of observed sources, requirement of a high stable frequency standard and frequency distribution system, small flux density of a radio source. We developed the system required for it, and make it clear that the VLBI system has the potential to measure a baseline with an accuracy of a few cm or less.The items studied in this project are as follows, 1) development of 22GHz VLBI system with phase-stabilized opical fiber link, 2) surveying radio sources at 22GHz and selection of the radio sources for the observation, 3) domestic VLBI observations with the system, 4)estimation of the baseline. The VLBI observations were carried out on two baselines of Mizusawa-Kashima (Communications Research Laboratory) and Mizusawa-Kagoshima. The error of the delay measured on the baseline of Mizusawa-Kashima was 59ps(1.8cm in path length) in the case of integration time of 258 sec, while the error was 82ps for 160 sec in S/X band. This result suggests that 22GHz VLBI is available for geodesy with an accuracy of a few cm or less.