大口径离轴非球面镜预应力环抛方法研究

提出了一种加工离轴非球面的预应力环抛方法,基于预应力加工方法的基本原理,利用环抛机来磨制离轴非球面.设计了一套专门的加载装置,将拼接镜面中具有不同离轴量的非球面子镜转化成曲率半径相同的球面子镜进行磨制,可以在同一台环抛机上进行抛光.利用这种方法,花费连续40 h的时间,磨制了一块按照中国30 m极大口径望远镜(CFGT)主镜参数比例缩小的离轴抛物面,顶点曲率半径21.6 m,离轴量3.6 m,离轴口径为330 mm,最大非球面度为16μm.试验表明该方法效率高,适用于批量加工,特别是极大口径天文望远镜拼接主镜的大批量非球面子镜研制.     

射电源法拉第旋率观测效应的模拟研究

由于受射电望远镜分辨率的限制,观测视线方向上可能有多源重叠现象.观测目标源的法拉第旋率(rotation measure,RM)及偏振角(polarization angle,PA)的测量值就会受到方向束内其它背景射电源的影响.通过模拟研究发现,背景射电源对目标源偏振参量测量的干扰形式与干扰源的RM值有关.只运用两三个...     

Upgrade Procedure for the Delingha 13.7-m Telescope

The 13.7-m millimeter-wave radio telescope of Purple Mountain Observatory operates at 3200-m above the sea level near Delingha, Qinghai Province, China. Equipped with a superconducting SIS receiver, the telescope is used in the millimeter-wave band ranging from 85 to 115 GHz. An upgrade procedure is reported here which includes a superconducting SIS receiver, a new phase-locked local oscillator, a dedicated multi-line backend system, and a new control system based on industrial computer with PCI bus. With the dedicated multi-line backend system, the CO and isotopic lines around 110 GHz are obtained simultaneously. In recent years, scientific activities with this telescope have been focused on studies of Galactic molecular clouds and star formation regions, including surveys of molecular lines from IRAS sources and large-scale map of molecular clouds. Other programs include studies of the circumstellar envelope of late-type stars and interaction of Galactic supernova remnants with dense molecular gas.     

Implementation of an optimized Cassegrain system for radio telescopes

We present the antenna design for a radio interferometer, the Arcminute Microkelvin Imager, together with its beam pattern measurement. Our aim was to develop a low-cost system with high aperture efficiency and low ground spill across the frequency range 12–18 GHz. We use a modified Cassegrain system consisting of a commercially available paraboloidal primary mirror with a diameter of 3.7 m, and a shaped secondary mirror. The secondary mirror is oversized with respect to a ray optics design and has a surface that is bent towards the primary near its outer edge using a square term for the shaping. The antennas are simple to manufacture and therefore their cost is low. The design increased the antenna gain by approximately 10 per cent compared to a normal Cassegrain system while still maintaining low contamination from ground spill and using a simple design for the horn.     

基于CSST的暂现源探测方法

中国巡天空间望远镜(China Space Survey Telescope, CSST)是中国载人航天工程规划建设的以大规模天文巡天为主任务的2m口径空间光学望远镜, 兼具高空间分辨率与大视场特性, 性能优异. 暂现源是CSST的重要科学目标之一. CSST作为空间望远镜, 与地面望远镜的图像噪声组成有着明显不同. 因此, 不能直接套用先前地基巡天项目的暂现源探测方案, 需要针对性开发专属的探测方法. CSST的暂现源探测方法以CSST仿真数据为基础进行开发、验证, 旨在尽可能准确地识别CSST主巡天数据中的暂现源. 方法以图像相减法为基础, 首先获得观测图像所对应残差图像, 并利用滤波方法给出残差图像泊松噪声分布; 然后使用渐变阈值间接统一背景噪声水平, 对残差图像进行目标源测光得到候选源列表; 最后, 通过判断候选源与当地泊松噪声的偏差对真实暂现源进行筛选, 结合原始图像信息与观测图像测光分类信息后, 进一步对候选源列表的假源进行剔除, 最终输出暂现源星表. 方法在共计20000个暂现源的多轮仿真测试中, 能够以平均95.9%的准确率对观测图像中的暂现源进行筛选. 相较于先前工作, 还更加全面且定量地给出了测试所得的不同亮度暂现源所对应的探测率. 测试结论验证了CSST暂现源探测方法的可行性、泛化能力与稳定性. 该方法也为空间望远镜暂现源探测任务提供了理论与编程基础.     

面向新疆奇台110 m射电望远镜宽带双极化Vivaldi馈源设计

射电望远镜一般要在宽频段内进行连续观测, 但传统相控阵天线设计方法难以兼顾宽频带和大角度扫描特性. 紧耦合天线的设计方法为宽带大角度扫描天线提供了新的设计思路, 基于此设计了一款宽带双极化 Vivaldi相控阵馈源. 首先结合Wheeler提出的连续电流片概念及等效电路对紧耦合原理进行理论分析, 然后针对Vivaldi天线分析了阵元间的强耦合能够有效拓展天线的工作带宽. 在此基础上设计了一款宽带Vivaldi相控阵馈源. 馈源阵列由8×9 Vivaldi天线阵元组成, 该阵列的工作带宽为2-8GHz, 并且能够在E面和H面均实现±$45^circ$的扫描特性. 最后对该馈源阵列进行了样机加工和测试, 测试结果与仿真结果具有较好的一致性.     

基于数值模拟的射电望远镜台址测风塔位置优选方法研究

射电望远镜天线结构设计和观测任务的正常进行都需要台址风场信息.随着望远镜性能要求的提高,天线结构设计越来越复杂,风载荷对天线观测时造成的指向影响也越发明显,如何在设计时保证结构刚度和强度,在观测时提高有效观测时间,都需要准确的风场数据.由于传统台址测风塔布置方法无法对测风塔拟设点的可靠性做出定量化评估,因此提出一种基于数值模拟优化测风塔位置的方法.数值模拟基于规范参数设置边界条件,与实测数据比较,整体趋势吻合,满足精度需求.对试验台址设置了4个测风塔位置,经分析P2点与天线位置的风速均方根误差值(root-mean-square error, RMSE)最小,测得的数据更能表征天线区域的风场特性.