基于ASHRAE晴空模型的25米天线面板热特性分析

天线面板在长时间的日照作用下,会因为热作用产生变形,了解天线面板的热变形,关键在于确定面板的温度场分布。在日照作用下,同样考虑天线自身的遮挡,其面板热分布显得比较复杂,难以确定。基于ASHRAE晴空模型,结合北京晴空模型的系数迭代回归公式,重点考虑了天线面板在夏至日受太阳辐射、与空气对流换热以及周围环境长波辐射等条件下的热流变化情况,利用有限元分析软件对天线面板在该天的温度场进行了数值模拟,给出了面板温度随时间的变化规律,有助于更好地了解天线面板变形和天线指向的校准。     

大型射电望远镜主反射面调整方法研究

随着毫米波天文学和空间通信的重要性日益提高, 对天线性能提出了越来越高的要求, 而天线性能往往受到其反射器表面精度的限制. 微波全息技术是一种快速有效的检测反射面天线表面轮廓的测量技术. 通过微波全息测量得到天线口径场, 计算天马65m射电望远镜反射面与理想抛物面的偏差. 天马65m射电望远镜的主反射面板是放射状的, 有14圈. 面板的每个角都固定在面板下方促动器的螺栓上进行上下移动, 且相邻面板交点处的拐角共用一个促动器. 采用平面拟合的方法可以计算各块面板拐角处的调整值, 但是同一个促动器会得到4个不同的调整量. 通过平面拟合, 同时以天线照明函数为权重的平差计算方法得到相邻面板拐角的一个平差值, 即天马65m射电望远镜1104个促动器的最佳调整值. 通过多次调整和新算法的应用, 天马65m射电望远镜反射面的面形精度逐渐提高到了0.24mm.     

德令哈13.7m望远镜重力变形研究

借助于数字摄影测量结果调整天线面板,使德令哈13.7 m望远镜在仰角52°时获得最佳反射面面形,从而使天线效率在观测仰角范围内得到整体优化.与之前基于经纬仪测量的面板调整结果相比,天线口径效率提高约1倍.依据不同俯仰姿态下的测量结果,得到了天线的重力变形模型,包括副面偏移和倾斜、主面焦距和面形偏差随仰角变化的规律.根据不同仰角的面形偏差测量数据反演反射面重力变形模型时,采用了数据拟合方法,这样可以减小测量误差对模型精度的影响.     

天线面板重力变形的主动控制量计算方法研究

提出了理想反射面及2参数、5参数和6参数最佳吻合抛物面方法,计算大型卡氏天线结构重力变形后主反射面板的调整量和对应的副反射面调整量,同时分析馈源偏焦对天线电性能的影响.以上海天文台天马65 m望远镜(TM65m)为研究对象,综合对比分析促动器调整量、6杆并联机构调整量、主反射面精度及偏焦后天线指向变化等,认为针对实际结构而言,经过调整修正后,6参数最佳吻合抛物面方法可以作为高精度天线理想的计算面板变形主动控制量方法,计算结果为天线的主动控制提供初调数据.     

基于全息测量的佘山25 m射电望远镜远场分析

首先分析了佘山25 m卡塞格伦天线结构,形变与噪声这2个因素影响下的远场进行仿真分析,理想情况比较,分析这2个因素对全息测量的影响。然后利用天线结构参数分别对天线面板表面获得了二维远场的幅度和相位分布图,并与     

基于主动反射面主动形变的相位恢复全息法研究

大口径射电望远镜的表面精度是影响天线性能的重要因素之一,受面板加工、安装以及重力、温度和风载的影响,极大地限制了天线的观测效率.基于较副面六联杆更加精确可控的主动面技术,首次采用泽尼克(Zernike)多项式表示连续变化的主动形变相位因子,通过调整主动面获取远场幅值,即可检测表面误差.通过建立数值仿真模型,计算了任意表面形变的恢复误差,并研究了在多种连续主动面变化下的表面形变恢复效果.结果表明此方法可以稳定精准地检测表面形变,从而有效提高射电望远镜的观测效率.     

十米天线极轴指向的调整

十米天线为赤道式,极轴的指向直接影响指向跟踪精度,因此需要仔细地进行检测和反复地调整。本文总结了十米天线极轴的检测及调整情况。     

佘山25米天线导轨问题对指向误差影响的研究

本根据25米射电望远镜方位导轨水平度的检测数据，分析了天线在不同位置时指向误差的情况及其原因，为进一步提高天线指向精度提供了理论依据和实测数据。     

十米天线电性能检测

本文介绍用射电天文方法测量云南天文台十米射电望远镜天线的效率η、天线噪声温度T_φ和第一旁瓣电平的基本原理和方法。测量结果表明,该天线以上三个主要参数都超过了原设计指标。在去年检测的基础上,今年又进行了复测,其结果与去年吻合较好。     

FAST单元面板面型检测算法研究

500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical Radio Telescope,FAST)是一个超大口径的可动望远镜,有三项技术创新,一是选址,二是轻型馈源索支撑,三是主动反射面。在主动反射面上,单元面板的面型和面板的出厂加工精度对电磁波在反射面的汇聚有很大影响。FAST主反射面由4 600块三角形反射面板拼接而成,每块面板为边长11 m三角形,这对FAST反射面面板的测量技术提出了更高的要求。摄影测量直接在影像上进行量测,无需接触物体本身;所摄影像信息丰富,可以从中获得所研究物体的大量几何信息和物理信息;适用于大范围、多目标测量,效率高。目前世界上最大的射电望远镜,如GBT和ARECIBO都是采用摄影测量技术进行反射面面形检测。在对现有的面型检测技术调研并试验后,提出基于数字近景摄影测量的方法,对FAST反射面11 m单元面板的面型进行检测,数分钟完成反射面板面型的一次检测,测量精度达到2.5 mm,经过调整后的单元面板的面型精度达到了3.0 mm,结果表明摄影测量应用于FAST反射面单元面板面型检测是可行的。     

40m射电望远镜天线副面和馈源偏移误差分析

建立40m口径天线结构的有限元分析模型,依据有限元分析结果,对副面和馈源偏离理想位置的偏移量和偏移误差进行分析与计算;从误差补偿角度,运用最佳指向技术对副面横偏误差进行补偿分析计算。误差补偿后的计算结果表明,副面横偏误差得到了大幅度的减小。分析计算结果为40m天线的实际工程提供了参考。     

An adjustment method for active reflector of large high-frequency antennas considering gain and boresight

The design of the Qitai 110 m Radio Telescope(QTT) with large aperture and very high working frequency(115 GHz) was investigated in Xinjiang, China. The results lead to a main reflector with high surface precision and high pointing precision. In this paper, the properties of active surface adjustment in a deformed parabolic reflector antenna are analyzed. To assure the performance of large reflector antennas such as gain and boresight, which can be obtained by utilizing an electromechanical coupling model, and satisfy them simultaneously, research on active surface adjustment applied to a new parabolic reflector as target surface has been done. Based on the initial position of actuators and the relationship between adjustment points and target points, a novel mathematical model and a program thatdirectly calculates the movements of actuators have been developed for guiding the active surface adjustment of large reflector antennas. This adjustment method is applied to an 8 m reflector antenna,in which we only consider gravity deformation. The results show that this method is more efficient in adjusting the surface and improving the working performance.     

A Research on the Gravity Deformation of Delingha 13.7m Telescope

Based on digital photogrammetric measurements, the antenna panels of the Delingha 13.7m radio telescope are adjusted to make the main dish have an optimal paraboloidal surface at the elevation of 52°, thus the overall antenna efficiency is optimized for different observing elevations. Observations indicate that the aperture efficiency of the telescope has been improved approximately twice in comparison with the antenna panels adjusted on the basis of theodolite measurements. According to the results of the measurements at different elevations, the models of antenna gravity deformation are built, including the displacement and tilt angle of the subreflector, as well as the focal length and surface error of the main reflector, as functions of elevation angle. In the process of modeling the gravity deformation of the main dish, instead of the direct calculation method, the least square fitting on the measured surface errors at different elevation angles is adopted, in order to reduce the effect of measurement errors on the accuracy of the model.     

Performance evaluation of lunar penetrating radar onboard the rover of CE-3 probe based on results from ground experiments

Lunar Penetrating Radar(LPR) onboard the rover that is part of the Chang'e-3(CE-3) mission was firstly utilized to obtain in situ measurements about geological structure on the lunar surface and the thickness of the lunar regolith, which are key elements for studying the evolutional history of lunar crust. Because penetration depth and resolution of LPR are related to the scientific objectives of this mission,a series of ground-based experiments using LPR was carried out, and results of the experimental data were obtained in a glacial area located in the northwest region of China. The results show that the penetration depth of the first channel antenna used for LPR is over 79 m with a resolution of 2.8 m, and that for the second channel antenna is over 50.8 m with a resolution of 17.1 cm.     

40m天线预测控制算法的研究

将预测控制的思想用于大口径天线跟踪系统的控制,提出了位置控制器的一种设计方案。并对天线的直流驱动系统进行建模和仿真实验。     

紫金山天文台13：7米射电望远镜天线表面精度的首次射电全息测量

１９９２年１月，在紫金山天文台１３．７米毫米波望远镜上进行了用射电全息术的相位恢复方法测量天线表面精度的尝试。利用望远镜的２２ＧＨｚ系统，用强水脉泽源ＯＲＩＯＮ－ＫＬ作为信号源测量了天线的聚焦和偏焦方向图，采用Ｍｉｓｅｌｌ算法获得了天线口面上的相位分布，由此得到的天线表面相对于理想抛物面偏差的均方根值与１９８９年用经典的经纬仪带尺方法测量的结果基本相符。     

Research on the panel adjustment method of an active main reflector for a large radio telescope

The surface accuracy of a large parabolic antenna is an important indicator to evaluate the quality of the antenna.It not only directly affects the antenna’s aperture efficiency,thereby determining the shortest wavelength that the antenna can work,but also affects the main lobe width and side lobe structure of the antenna pattern.Microwave holography is an important method for parabolic antenna profile detection.In this article we adopt a new algorithm to adjust the panels for the large radio telescope with an active main reflector through the TM65 m antenna’s aperture phase profile.The panels of the TM65 m radio telescope is in a radial pattern with 14 rings.Each corner of the panel is fixed on the screw of the actuator to move up and down,and the adjacent corners of the four panels share an actuator.We use the method of plane fitting to calculate the adjustment value of every panel’s corner.But one actuator,which simultaneously controls the common corner of the adjacent panels,will have different adjustment values according to the different plane fitting equation based on adjacent panels.In this paper,the adjustment value of the adjacent panels’crosspoints are constrained to be equal to the constraint condition to calculate each actuator’s adjustment value of the TM65 m radio telescope.Through multiple adjustments and application of the new algorithms,the accuracy of the TM65 m antenna reflector profile has been improved from the original 0.28 mm to the current 0.19 mm.     

环焦天线口径面相位分析

环焦天线具有特殊的电磁特性和应用领域.对环焦天线的口径面相位误差进行了理论和仿真分析,推导了馈源和副面位置偏差引起的相位误差、主副面之间的补偿关系以及全息测量中天线转动引起的光程差.研究结果将对环焦天线的精确面形测量和补偿提供理论依据和参考.     

Effective area of the antenna of the RT-22 CrAO RI radio telescope

Based on the results of calibrator observations at 13.5-mm and 8.2-mm wavelengths in 1985 and 2005, the dependence of the effective area of the RT-22 CrAO RI antenna on ambient temperature and elevation was determined. The obtained results confirm a high quality of the RT-22 antenna at millimeter wavelengths. A high accuracy of the reflector surface makes it possible to observe at millimeter wavelengths right to 2 mm. At 8.2-mm wavelength, the effective area changes by no more than 5% when the antenna is reinstalled from the zenith to 15° elevation angle. Large antennas, intended to operate at maximum frequencies, should be built either taking into account the climatic conditions of the antenna sites or taking measures to provide thermal stability of the antenna.