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

1. 研究目标：(1)实现地球变自转的高精度测量。(2)实现日本鹿岛与美国佛罗里达州里士满的高精度时间同步。(3)进行数据分析，完善数据分析软件。(4)建立跨大西洋VLBI网络（IRIS-P）平稳运行的管理制度。合作机构：虽然研究小组完全由国家天文台的工作人员组成，但这项研究是与两个机构密切合作进行的，即通信研究实验室（CRL，日本）和国家大地测量局（NGS，美国）。2 . CRL提出在岛使用K-3 VLBI系统，NGS提出安排美国台站参与IRIS-P网络，并在美国海军天文台相关中心进行观测录像带的关联。研究计划：(1)1987年：启动由…More CRL（日本）的鹿岛所组成的IRSI-P网络。Richmond (Florida， USA), Ft. Davis （Texas， USA）和Fairbanks （Alaska， USA）作为获取符合研究目标的数据的网络中心，进行数据分析，并将结果与CRL和NGS进行比较。(2) 1988年：在1987年观测结果的基础上改进观测计划，改进分析软件。研究活动：(1)观察：完全按计划进行每月24小时的观察，每次向鹿岛派出3名观察员。(2)网络运行：从网络建立起半年之内，建立了从相关中心运送磁带和通过电子邮件向参与台站发送观测时间表的系统。(3)数据分析和软件改进：在CRL合作的帮助下，对我们的软件得到的结果进行了仔细的检查，并进行了必要的改进。1988年6月，研究组的S. Manabe访问NGS，讨论数据分析问题。最终，目前使用的软件作为iris - p - 5的网络中心，具备了足够的数据分析能力。科学发现：(1)测定地球自转精度优于1厘米。因此，IRIS-P网络是现有三种VLBI网络中性能最好的。(2)银河系外类星体的位置误差在几毫角秒量级。(3)将参与台站的位置与全球地面参考系进行了定位，精度为几厘米。(4)实现了岛与列治文的时间同步，精度为0.5 ns。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