Development of surface measuring system for large-diameter antennas using satellite signals.

大直径高精度天线，如Nobeyama 45米望远镜和IRAM 30米望远镜已用于毫米和亚毫米波射电天文学。高分辨率表面测量技术对提高天线的表面精度具有重要意义。最近，无线电全息术被普遍用于这一目的。但是，为了将该技术应用于毫米波和亚毫米波的大直径天线，需要进行尽可能高精度的研究。在开发科学研究补助金项目中，开发了使用地球同步卫星信号的无线电全息系统。该系统由双通道相关接收机、控制系统和数据处理软件组成。作为发射机，使用了来自日本通信卫星CS-2a和2b的19.45 GHz无线电信标信号。利用该系统，于1985年10月和1986年8月对45米望远镜的表面进行了53次测量，测量分辨率分别为64 × 64（分辨率86厘米）和128 × 128（分辨率43厘米）。根据最佳重复性的测量结果，对表面进行了调整，并从200 m rms提高到150 m rms。通过误差分析、散射波抑制实验和指向误差影响的计算机仿真研究，为今后的发展提供了有价值的结果。

Large-diameter high-precision antenmas such as Nobeyama 45 m telescope and IRAM 30 m telescope have been used for millimeter and submillimeter wave radio astronomy. High-resolution surface mesurering techniques are very important to improve the surface accuracy of these antennas. Recently, radio holography is universally used for this purpose. But, the research has been needed to achieve highest possible accuracy in applying this technique to large-diameter antennas used for millimeter and submillimeter wave length.In this Grant-in-Aid for Developmental Scientific Research, a Radio holography system using geostationary satellite signals was developed. The system consists of 2-channel correlation receiver, control system, and softwares for data reduction. As a transmitter, radio beacon signals at 19.45 GHz from the Japanese communications satellites CS-2a and 2b were used. we succeeded in developing the system which has good phase stability, high sensitivity, and good isolation.By the use of this system, the surface of the 45 m telescope was measured 53 times in total in both 64x64 (resolution 86 cm) and 128x128 (resolution 43 cm) measurements in October 1985 and August 1986. Based on the measurements of best repeatability, the surface was adjusted and improved from 200 m rms to 150 m rms. Valuable results were obtained for future developments from the analysis of errors, experiments to reduce the effect of scattered wave, and computer simulations to investigate the effect of pointing error.