大口径射电望远镜面形精度离焦全息法快速测量技术研究

基于有限元模型的主动反射面技术无法模拟复杂的天气环境（如阳光照射、阵风）以及天线焊接、安装等因素导致的天线面形误差，需要一种快速测量的方法来形成闭环反馈。以往的经纬仪测量法、摄影测量法和相位干涉全息法等都不能满足快速测量需求，新发展的离焦全息法具有测量速度快、测量精度高、可任意俯仰测量、无需额外硬件设备等诸多优势，适合对天线的快速测量反馈。美国GBT已将该方法应用于其主动面系统中，并取得了较好的效果，但其单次测量仍需20分钟，只能达到准实时半闭环控制的效果。本课题将在南山25米射电望远镜上建立离焦全息法测量系统，对影响测量速度和精度的因素进行详细解析，优化测量方案、改进相位恢复算法、采用GPU分析计算、利用多波束馈源观测等方法多管齐下使测量时间缩短至几分钟以内，以期基本满足实时检测闭环反馈的要求，并展开该方法嵌入主动面系统关键问题的研究，为我国百米级全可动大口径射电望远镜的建设作出保障。

In order to decrease the deformation of antenna surface due to the effects of gravity, temperature and wind, a method use active surface system based on the Finite Element Model has been adopted. But, many errors are also cannot be simulated in this model,such as the process of welding and installing,complicated envirment such as sunlight and gust and so on.So, we need a real-time detection method for better compensation the antenna surface error.The former methods such as theodolitic survey, photogrammetry and phase reference holography cannot meet this steep demand. Nevertheless, a new method — Out-Of-Focus holography which has higher speed, better accuracy, measurement at arbitrarily elevation and non-hardware auxiliary developed recently and got a fine performance after use in the GBT.But, a single measurement still need 20 minutes, only to achieve the effect of near real time detection and a half closed-loop control.Firstly, we will be studying the fundamental principle of this method and setting up a measurement system based on the Nanshan 25m telescope. Secondly, we will be analysising the factors which affect the measurement speed and accuracy.And we will be reducing the measuring time to several minutes by the method of optimizing observe scheme,improving phase retrival algorithm,utilzing GPU to calculation,using multi-beam feed and so on.Several problems of embedded this method into the active surface system forming a close-loop control system will be considered in this project.This method will be using in the large moveable telescope for increasing the antenna efficiency and achieving high frequency observation.