上海天马望远镜主动面动态形变的测量和调整技术研究

The Tian Ma telescope adopts active surface to modify dynamic deformation of the main surface for the first time in the domestic large radio telescopes. The dynamic deformation is caused by gravity, temperature and other time-varying factors. In order to modify the dynamic deformation real-timely and accurately by using active surface, the project researches the techniques for measurement and adjustment of dynamic deformation based on the characteristics of the Tian Ma telescope and phase retrieval holography. The specific contents are as follows. Firstly, the modeling methods of the simulated observation data are researched based on the defocus positions, pointing errors and signal-to-noise ratios by using the Autoregressive model, the Gaussian model, and the calculation software, and by combining with the measurement. Secondly, the fast extraction algorithm for dynamic deformation is implemented based on the simulated observation data by calculating the antenna aperture field function, and by adopting step calculation method and least-square iteration method. Thirdly, the fast and high-accuracy measurement of high-frequency antenna pattern is implemented by studying the On-The-Fly observing mode, noise removal techniques, and fast data preprocessing method for the maser source. Finally, the mathematic relation between the aperture phase distribution and actuator adjustment quantity is derived. The calibration method of those two coordinate systems is studied. The different class techniques for adjustment verification are implemented. The project will establish a complete set of measurement and adjustment methods. The methods will be used to modify the dynamic deformation of the Tian Ma telescope active surface. The research methods of the project are universal, and can be used for the application of active surface systems of other large radio telescopes.

天马望远镜在国内大型射电望远镜领域首次采用主动面以修正重力和温度等时变因素引起的主面动态形变。为实现天马望远镜主动面对动态形变的实时和精确修正，本项目基于天马望远镜的特点及相位恢复全息测量技术研究动态形变的测量和调整技术。具体内容包括：采用自回归模型和高斯模型，借助计算软件，并结合实测，实现基于离焦位置、指向误差和信噪比三个变量的仿真观测数据建模方法；计算天线口径场函数，采用分步计算和最小二乘迭代法，基于仿真观测数据，实现快速动态形变提取算法；研究脉泽源观测的飞行模式、噪声去除技术和快速数据预处理方法，实现高频段天线方向图的高精度快速测量；推导口径面相位分布与促动器调整量之间的数学关系，研究两者之间坐标系标定方法，并实现不同级别的调整验证技术。本项目将建立一套完整的测量和调整方法，以此来修正天马望远镜主动面的动态形变。本项目的研究方法具有通用性，可为其它大型射电望远镜主动面的应用提供参考。

大口径射电望远镜具有高灵敏度和高分辨率的优势，在天文研究和深空探测中发挥着重要作用。但是受重力和温度等因素的影响，大口径射电望远镜的主反射面会发生形变。此时仅仅依靠保形技术已经无法保证射电望远镜在高频观测时的工作效率，必须调整主反射面形状，使之与理想形状相吻合，才可以满足电性能指标的要求。为此天马射电望远镜在国内大型射电望远镜上首次采用主动面系统，以修正重力和温度形变。本项目研发了扩展离焦全息测量技术，在国内首次实现大型射电望远镜主反射面重力形变和温度形变的测量和调整。本项目研究成果直接应用于天马望远镜。天马望远镜采用本研究成果顺利完成验收，总体性能位于世界前三。本项目的研究成果具有重要的应用前景，可应用于QTT以及深空网大型射电望远镜。本项目的测量数据可提供给我国的天线制造单位，为天线制造单位的天线设计提供参考。