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

本研究的目的是研究甚长基线干涉仪(VLBI)的国际活动，以便在日本VLBI(用于地球自转研究和天体测量的VLBI)系统中建立更精确的VLBI系统。在德国的Wettzell‘s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的研究。VLBI后端的兼容能力对数据采集终端提出了强烈的要求。电波传播的超额路径延迟(EPD)在晴朗的日子里，EPD可以很好地确定。但在有降雨和大阴天的情况下，大气中水汽的测量可以由甚高频、无线电声学探测系统和降水来确定。用VLBI后端进行国际合作观测K4后端系统K4的德国航空航天中心和后端系统为Mrak 3的Nobeama射电观测站之间进行了VLBI实验观测，并证明了K4和Mark 3.5之间的兼容性。VLBI后端的兼容性和相关器的研究在美国干草堆天文台，一个新的后端Mark 4正在开发中，并且已经研究了Mark 4相关器。美国海军天文台一直在运行Mark 3A相关器。为了使VLBI网络顺利运行，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.