共查询到18条相似文献，搜索用时 93 毫秒
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《中国科学院上海天文台年刊》2014,(0)
上海65米射电望远镜是亚洲最大、全方位可转动的大型射电望远镜,在国内首次配备主动面系统。对主动面系统应用的关键技术——偏焦全息测量技术在上海65米射电望远镜中的初步应用情况进行介绍。首先,介绍常用的天线主反射面面型测量方法。接着,介绍偏焦全息测量技术的应用方法。采用飞行扫描,利用X波段致冷接收机和连续谱终端,将射电源3C84作为信号源,通过移动副反射面测量得到一幅聚焦天线方向图和两幅偏焦天线方向图。将三幅天线方向图作为偏焦全息测量算法的输入,获得天线口径面相位分布的Zernike系数。依据Zernike系数计算得到天线主反射面型面误差的均方根值(root mean square,RMS),该均方根值与前期照相测量的结果基本相符。最后,对今后的改进工作进行展望。 相似文献
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天线反射面的面形精度直接影响天线效率, 是望远镜的关键指标之一. 近场射电全息具有测量精度高, 便捷高效的优点, 是毫米波和亚毫米波射电望远镜面形检测最为常用的方法之一, 卡焦近场全息可以完整测量望远镜光路中整体的面形误差. 斜轴式机架结构能够更好地适应太赫兹望远镜在极端台址环境下的整体保温和热控需求, 但斜轴天线特殊的转动特性会在近场全息测量过程中引入额外的系统误差. 针对斜轴式天线的卡焦近场全息测量, 分析了数据处理中需要额外考虑的参考路接收机位置和副面衍射的影响, 并在1.2m口径斜轴式太赫兹天线上开展了测量实验. 实验结果表明, 卡焦近场全息测量的重复测量精度优于2.0μm RMS (Root Mean Square), 面形误差分布与摄影测量所得结果一致, 验证了误差分析与修正的正确性. 相似文献
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《天文研究与技术》2017,(3)
南山25 m射电望远镜经过一年多的升级改造现已全面完成,主反射面直径增加至26 m,为保证Q波段(30~50 GHz)接收机的工作效率,望远镜的表面精度需达到较高的水平,微波全息法可对天线面形进行精确测量和调整,是望远镜面形首次和定期精调的首选,基于新南山26 m天线建立了一套全息法测量系统。整个系统包括参考天线、接收机、相关机、传输链路、时频参考、扫描控制和全息法处理软件等几部分,采用带通采样技术直接采集中频信号,减少了基带信号转换环节;采用高性能外部本振并利用氢钟输出的参考信号进行锁相,达到了极高的相位稳定度。目前整个系统已通过测试并取得了初步的测量结果,经处理分析,该系统工作正常,已达到应用要求。 相似文献
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基于数字摄影测量技术的13.7m毫米波天线面形检测 总被引：2，自引：0，他引：2
将工业数字摄影测量技术首次应用于13.7 m毫米波射电望远镜天线的面形精度检测中.为克服现场条件的限制,在测量中使用环形轨道输送相机,采用无线传输的方式进行现场摄影.采用回光材料制作人工的标志,利用编码标志完成摄站的自动定向和同名点匹配,用光束法平差的方法解算点的3D坐标.利用CAD面形转换法和自由拟合法计算面形偏差,最终480个调整点的面形CAD拟合后的偏差调整到了0.083 mm.验证了摄影测量在射电天文天线测量中的可行性和优越性. 相似文献
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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。 相似文献
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描述了采用光学望远镜辅助天马13m射电望远镜进行指向测量以及建立指向误差修正模型的方法. 对于小口径望远镜, 指向校准目标源比较少, 用射电法建立指向模型难以覆盖全天区. 利用上海天文台天马13m射 电望远镜进行光学望远镜辅助射电望远镜指向测量研究, 在13m天线背架上安装一套光学指向系统, 获得了优 于3''的重复测量误差. 此外, 通过对影响天线指向因素的分析, 建立了包含8个误差项的指向误差修正模型以及 光轴和电轴偏差模型. 将指向模型代入天线伺服控制系统, 对校准目标射电源进行十字扫描, 得到指向样本残差约 为5''. 该研究可以为实现高精度指向建模提供一种参考方法. 相似文献
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针对大口径射电望远镜主反射面在日照作用下产生温度梯度及形变问题,建立了完整的温度测量及精度评估的系统。在特定的测量条件下,利用红外热像仪测量了望远镜主反射面的温度,获得了不同时刻的温度分布情况,并得到最大温差为7.8℃。采用全息法分析主反射面的精度变化情况,得到由于温度变化导致的最大误差为0.33 mm。结果表明:温度对望远镜主反射面的精度影响较大,需采取合适的测试系统实时监测温度,并调整主反射面板以提高精度。 相似文献
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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. 相似文献
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《天文和天体物理学研究(英文版)》2016,(8)
A subreflector adjustment system for the Tianma 65 m radio telescope, administered by Shanghai Astronomical Observatory, has been installed to compensate for gravitational deformation of the main reflector and the structure supporting the subreflector. The position and attitude of the subreflector are variable in order to improve the efficiency at different elevations. The subreflector model has the goal of improving the antenna's performance. A new fitting formulation which is different from the traditional formulation is proposed to reduce the fitting error in the Y direction. The only difference in the subreflector models of the 65 m radio telescope is the bias of a constant term in the Z direction. We have investigated the effect of movements of the subreflector on the pointing of the antenna. The results of these performance measurements made by moving the antenna in elevation show that the subreflector model can effectively improve the efficiency of the 65 m radio telescope at each elevation. An antenna efficiency of about 60% at the K u band is reached in the whole angular range of elevation. 相似文献
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Ying-Xi Zuo Yang Li Ji-Xian Sun Ji Yang Jing-Jing Li Ye Xu Deng-Yun He Qin-Hong Fan Sheng-Hong Fan 《Chinese Astronomy and Astrophysics》2011,35(4):439-446
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. 相似文献
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MEI Geng-jun XIANG Bin-bin WANG Na WANG Zhao-jun 《Chinese Astronomy and Astrophysics》2021,45(2):236-251
The pointing accuracy of a radio telescope is usually less than one-tenth of its antenna beam width. For large-aperture antennas at the short-centimeter band or millimeter-wave band, the pointing accuracy must be as high as several arc seconds. Therefore, for large-diameter and high-frequency reflector antennas, the pointing problem has become an important focal point to realize the antenna performance. Among many structural subsystem factors that affect the antenna pointing accuracy, there has been only less study on the factor of main reflector deformation. Based on the structural characteristics of the antenna, a reflector space coordinate system is established in this paper. And based on the space coordinates of the main reflector surface points after deformation, a non-linear least squares fitting method with 3 degrees of freedom is proposed to accurately predict the antenna pointing. Finally, the space geometric relationship is used to strictly derive the precise adjustments on the elevation and azimuth in order for correcting the antenna pointing error, and the indirect relationship between the main reflector deformation and the pointing error is constructed. This has certain guiding significance for improving the pointing accuracy of large radio antennas. 相似文献
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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 总被引：2，自引：0，他引：2
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。 相似文献
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《天文和天体物理学研究(英文版)》2016,(8)
DATE5,a 5 m telescope for terahertz exploration, was proposed for acquiring observations at Dome A, Antarctica. In order to observe the terahertz spectrum, it is necessary to maintain high surface accuracy in the the antenna when it is exposed to Antarctic weather conditions. Structural analysis shows that both machined aluminum and carbon fiber reinforced plastic(CFRP) panels can meet surface accuracy requirements. In this paper, one design concept based on aluminum panels is introduced. This includes panel layout, details on panel support, design of a CFRP backup structure, and detailed finite element analysis.Modal, gravity and thermal analysis are all performed and surface deformations of the main reflector are evaluated for all load cases. At the end of the paper, the manufacture of a prototype panel is also described.Based on these results, we found that using smaller aluminum reflector panels has the potential to meet the surface requirements in the harsh Dome A environment. 相似文献
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《天文和天体物理学研究(英文版)》2020,(1)
This paper proposes an active sub-reflector suitable for large radio telescopes, which can compensate both of the deformation of the main reflector and sub-reflector position offsets. The mathematical formula of the main reflector deformation compensated by the sub-reflector is deduced based on Cassegrain and Gregory antenna structures. The position of the sub-reflector is adjustable to compensate for defocusing errors on high and low elevations, which are mainly caused by the deformation of the sub-reflector supporting legs. In this paper, the method of obtaining the optimum position of the sub-reflector from the aperture phase by the interferometric method is introduced. The actual measurement is verified on the Tianma 65 m radio telescope, which provides a new way to diagnose the position error of the sub-reflector. 相似文献
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Xiao-Qiang Tang Jin-Song Wang Qi-Ming Wang Department of Precision Instruments Tsinghua University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2003,3(5):478-490
We propose a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees of rotations and one degree of translation to support the active reflector units of a large spherical radio telescope. The kinematics, workspace and accuracy of the mechanism are analyzed. One-dimensional and two-dimensional fitting errors to the working region of active reflector are investigated. Dimensional parameters of the mechanism and active reflector unit are examined with respect to the requirement of fitting accuracy. The result of accuracy analysis shows the effectiveness and feasibility of the proposed mechanism, and gives a design rule to guarantee the highest working frequency required by large radio telescope. 相似文献