为快速测量射电望远镜主反射面的动态形变,提高高频观测效率,利用多波束天线方向图具有相似性和重叠性的特征,基于相位恢复法提出了一种快速测量方法。首先将各波束的部分聚焦和离焦天线方向图减去其相对于中心位置的指向偏差,然后拼接为中心波束的完整聚焦和离焦天线方向图;接着采用Levenberg-Marquardt算法最小化该拼接天线方向图和理论天线方向图的残差,计算出反映主反射面动态形变成分的低阶Zernike多项式系数,从而获得主反射面的动态形变。基于7波束Q波段的数值仿真实验表明,该方法能够在5 min内以55 μm的测量精度测得射电望远镜主反射面的动态形变,且具有较好的抗噪声、抗幅度波动等优点,可应用于90 GHz以下的天文观测。

A fast method to measure the primary surface dynamic deformation of a radio telescope for improving high-frequency observation efficiency is proposed based on the similarity and overlap of the multibeam patterns, and the phase retrieval method. Firstly, the pointing offsets relative to the center are subtracted from a part of in-focus and defocus patterns of each beam, and these patterns are spliced to construct a group of complete in-focus and defocus patterns of the center beam. Secondly, the sum of squared residuals by which the splicing patterns differ from the theoretical ones is minimized based on Levenberg-Marquardt algorithm, to calculate the coefficients of Zernike polynomials, and the primary reflector dynamic deformation is retrieved. The numerical simulation experiment based on the 7-beam Q-band shows that the proposed method can retrieve the primary reflector dynamic deformation of the radio telescope in 5 min with the measurement accuracy of 55 μm, with the advantages of anti-noise and anti-fluctuation, and can be applied for the astronomical observations below 90 GHz.