Establishment of the Trans-Pacific VLBI Network for Monitoring the Earth's Variable Rotation

1.研究目标：(1)实现对地球自转的高精度测量。(2)实现日本鹿岛和美国佛罗里达州里士满之间的高精度时间同步。(3)开展数据分析，完善数据分析软件。(4)建立管理制度，使跨大西洋VLBI网络(IRIS-P)顺利运行。合作研究所：虽然研究小组仅由国家天文台工作人员组成，但这项研究是与两个研究所密切合作进行的，即通信研究实验室(CRL，日本)和国家大地测量(NGS，美国)。CRL在鹿岛提供了K-3VLBI系统的使用，NGS提供了参加IRIS-P网络的美国站的安排，以及美国海军天文台相关中心的观测录像带的关联。研究计划：(1)1987年：启动由…鹿岛组成的IRSI-P网络更多CRL(日本)。美国佛罗里达州里士满戴维斯(美国得克萨斯州)和费尔班克斯(美国阿拉斯加州)，并作为网络中心顺利运行，以获取满足研究目标的数据，并进行数据分析，并将结果与CRL和NGS的结果进行比较。(2)1988年：在1987年观测结果的基础上改进观测计划，完善分析软件。研究活动：(1)观测：按计划每月24小时全程观测，每次派3名观察员前往鹿岛。(2)网络运行：在网络启动后的半年内，建立了向相关中心运送磁带并通过电子邮件向参与站发送观测计划的系统。(3)数据分析和软件改进：在CRL的配合下，对我们软件的结果进行了仔细的检查，并做出了必要的改进。1988年6月，研究小组的S.Manabe访问了NGS，讨论了数据分析方面的问题。最终，目前使用的软件作为IRIS-p.5的网络中心，具有足够的数据分析能力。科学发现：(1)我们测定了地球自转，精度优于1厘米。因此，在现有的三种VLBI网络中，IRIS-P网络是最好的。(2)我们发现了几毫角秒量级的河外类星体的位置误差。(3)将各参测站的位置与全球陆试参考系进行了定位，精度为几厘米。(4)实现了鹿岛与里士满之间的时间同步，同步精度为0.5 ns。较少

1. Objectives of the Research: (1) To achieve high-precision measurement of the Earth's variable rotation. (2) To achieve high-precision time synchronization between Kashima (Japan) and Richmond (Florida, USA). (3) To conduct data analysis and improve data analysis software. (4) To establish the management system to smoothly operate the Trans-Atrantic VLBI network (IRIS-P).2. Cooperative Institutes: Although the research group consists solely of the National Astronomical Observatory staff, this research was carried out in close cooperation with two institutes, namely the Communications Research Laboratory (CRL, Japan) and the National Geodetic Survey (NGS, USA). CRL offered the use of K-3 VLBI system at Kashima, and NGS offered the arrangement of the US stations participation in IRIS-P network, as well as correlation of observed video tapes at the correlation center in the United States Naval Observatory.3. Research Plans: (1) 1987: To initiate the IRSI-P network composed of Kashima of … More CRL (Japan). Richmond (Florida, USA), Ft. Davis (Texas, USA), and Fairbanks (Alaska, USA) and operate it smoothly as the network center for acquiring the data which meet the reseatch objectives, and to conduct data analysis and compare the results with those of CRL and NGS. (2) 1988: To improve observation schedule based on the results derived from 1987 observations, and to refine analysis software.4. Research Activities: (1) Observation: Monthly 24-hour session observations were completely made as scheduled, by sending 3 observers to Kashima every time. (2) Network Operation: Within half a year from the initiation of the network, the system was established to shipping tapes to and from the correlation center and to send observation schedules to the participating stations through an electronic mail. (3) Data Analysis and Software Improvement: With the aid of CRL cooperation, the results obtained by our software were carefully examined and thereby necessary improvement was made. In June 1988, S. Manabe of the research group visited NGS to discuss matters on data analysis. Eventually, the presently used software has sufficient capability for data analysis as the network center of IRIS-P.5. Scientific Findings: (1) We determined the Earth's rotation with the precision better than 1 cm. Thus the IRIS-P network is the best among existing three VLBI networks. (2) We found errors of the positions of extragalactic quasars of the order of a few milli-arcseconds. (3) We tied the positions of the participating stations with the global terretrial reference system with the precision of a few cm. (4) We achieved time synchronization between Kashima and Richmond with the precision of 0.5 ns. Less