Study of the Earth Rotation and the Space Positioning with a Newly Precise VLBI Method

本研究的目的是研究VLBI（甚长基线干涉仪）的国际活动，以便在日本建立一个更精确的VLBI系统，VERA （VLBI for The Earth Rotation study and Astrometry）。在澳大利亚、美国、加拿大、德国、瑞典、荷兰和英国进行了调查，主要结果如下：天线和VLBI系统对新旧大型射电望远镜进行了研究。在德国Wettzell的天线上，天线参考点的位移和天线光学系统的变形得到了很好的校正。对VLBI硬件系统和相关器进行了前端、频率标准、相位延迟校准器和光纤系统等方面的研究。数据采集终端对VLBI后端兼容能力提出了强烈的要求。无线电波传播的额外路径延迟（EPD）在空气晴朗的日子，EPD是可以确定的。但在降雨和重阴天的情况下，大气中水蒸气的测量可以通过甚高频、无线电声学探测系统和降水来确定。K4 VLBI后端国际合作观测德国Hochfrequenztechnik研究所DLR用便携式VLBI后端系统K4与Nobeyama射电天文台用后端系统Mrak 3进行了VLBI实验观测，并证明了K4与Mark 3.5的兼容性。美国干草堆天文台正在研制一种新的后端马克4，并对马克4相关器进行了研究。美国海军天文台一直在操作Mark 3A相关器。为了使VLBI网络正常运行，需要对VLBI磁带进行管理。

The purpose of this study is, to research international activities of the VLBI (Very Long Baseline Interferometer) to establish a much more accurate VLBI system in Japan, VERA (VLBI for the Earth Rotation Study and Astrometry).Investigations have been made in Australia, U. S. A., Canada, Germany, Sweden, Netherland and U. K. Main results are as follows :1. Antenna and the VLBI systemOld and new large radio telescopes were investigated. Displacements of the reference point of the an tenna and deformations of the optical system of the antenna were well corrected at Wettzell's antenna, Germany.2. The VLBI hardware systems and correlatorsResearches were made on the frontend, frequency standard, phase delay calibrator and optical fiber system. Data acquisition terminals are strongly requested for the capability of compatibility ofthe VLBI backend.3. Excess path delay (EPD) of the radio wave propagationThe EPD are well determined in the clear-air day. But in the case of rainfall and heavy cloudy days measurements of water vapor in the atmosphere may be determined by VHF, Radio Acoustic Sounding System and the precipitation.4. International cooperative observation with the VLBI backend K4Experimental VLBI observations between the DLR, Institute fur Hochfrequenztechnik, Germany with the portable VLBI backend system K4 and the Nobeyama Radio observatory with the backend Mrak 3 have been made and proved the compatibility between K4 and Mark 3.5. Compatibility of the VLBI backend and study of the correlatorAt Haystack Observatory, U. S. A. a new backend Mark 4 is now developing and the Mark 4 correlator has been studied. The United States Navy Observatory has been operating the Mark 3A correlator. It needs management of the VLBI tapes in order to operate the VLBI network smoothly.