标题： 弗雷德·杨亚毫米波望远镜的全息表面测量系统 显示英文标题

标题： Holographic surface measurement system for the Fred Young Submillimeter Telescope

摘要： 我们描述了一个正在开发的系统，用于测量弗雷德·扬亚毫米波望远镜（FYST）的反射镜形状，该望远镜目前正在为CCAT天文台建造。“全息”天线测量技术是一种高效且精确测量大型毫米波望远镜表面的方式，并且具有在实际运行条件下测量整个系统波前误差的优势，例如在夜晚暴露的场地。 然而，将其应用于FYST带来了显著挑战，因为需要极高的精度，望远镜由两个大口径非对称反射镜组成，并且要求无需人员在场即可进行测量。 我们使用高频（~300 GHz）源，该源相对接近望远镜孔径（小于费涅尔距离的1/100），以最小化大气影响。 主接收器位于接收舱内，可通过远程控制移动到不同位置，从而测量焦平面不同部分的波前误差。 放置在轭架上的第二个接收器提供相位参考。 信号在数字交叉相关光谱仪中组合。 扫描望远镜可生成复杂的波束图。 通过推理找到表面误差，即我们制作带有误差的反射面模型并计算预期图案，然后迭代以找到与数据的最佳匹配。 为此，我们开发了一种快速准确的方法，利用基尔霍夫-菲涅耳公式计算图案。 本文详细介绍了设计细节，并概述了测量和推理过程模拟的结果。 这些结果显示，可以实现约3微米均方根的测量精度。 显示英文摘要

摘要： We describe a system being developed for measuring the shapes of the mirrors of the Fred Young Submillimeter Telescope (FYST), now under construction for the CCAT Observatory. "Holographic" antenna-measuring techniques are an efficient and accurate way of measuring the surfaces of large millimeter-wave telescopes and they have the advantage of measuring the wave-front errors of the whole system under operational conditions, e.g. at night on an exposed site. Applying this to FYST, however, presents significant challenges because of the high accuracy needed, the fact that the telescope consists of two large off-axis mirrors, and a requirement that measurements can be made without personnel present. We use a high-frequency (~300GHz) source which is relatively close to the telescope aperture (<1/100th of the Fresnel distance) to minimize atmospheric effects. The main receiver is in the receiver cabin and can be moved under remote control to different positions, so that the wave-front errors in different parts of the focal plane can be measured. A second receiver placed on the yoke provides a phase reference. The signals are combined in a digital cross-correlation spectrometer. Scanning the telescope provides a map of the complex beam pattern. The surface errors are found by inference, i.e. we make models of the reflectors with errors and calculate the patterns expected, and then iterate to find the best match to the data. To do this we have developed a fast and accurate method for calculating the patterns using the Kirchhoff-Fresnel formulation. This paper presents details of the design and outlines the results from simulations of the measurement and inference process. These indicate that a measurement accuracy of ~3 microns rms is achievable.