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.     

射频干扰检测的SumThreshold算法

射频干扰(Radio Frequency Interference, RFI)是射电目标搜寻和精确分析研究的关键影响因素,因此RFI检测是相关数据处理中的一个重要环节.已有RFI检测方法可分为成分分解法、阈值分析法、机器学习类方法.从应用广泛性和可解释性方面考虑,阈值分析法最具代表性,特别是SumThreshold是近年备受关注的一个RFI检测方法.从SumThreshold方法的原理、算法设计、优化要点、适用性等方面进行介绍和探讨,以供同行参考.     

德令哈13.7m望远镜多波束接收机的运行

德令哈13.7 m望远镜是中国最重要的射电望远镜之一.望远镜自安装超导成像频谱仪以及采用飞行观测模式以来,运行近10 yr.在此期间,望远镜开展并完成大量的天文观测,累积了巨量的天文数据,取得了一系列重要的科研成果.介绍了超导成像频谱仪在天文观测中的运行状态,运行中疑难问题、故障现象及解决方案.详述了超导成像频谱仪各方面性能测试及多年来的性能分析,包含接收机噪声温度及望远镜系统噪声温度、镜像抑制比、接收机稳定性、波束性能等方面.列举了超导成像频谱仪更新发展方面的工作,包含本振功率自动化调整、边带分离型超导混频器预放大电路的更新、控制程序的优化等.总结经验和规律,承前启后,将过去的超导成像频谱仪的维护运行经验应用到之后新一代大规模接收机系统中.     

德令哈13.7m望远镜热变形研究

热变形是影响大型毫米波天线性能的关键因素之一.这种变形会改变天线反射面的轴线和焦距、恶化反射面面形,导致天线效率和指向精度恶化,同时也使天线效率和指向的长时间稳定性降低.由于太阳的周日运动,造成望远镜4个主支撑腿(简称支腿)之间存在温差,且该温差是变化的,从而引起方位轴的倾斜周期性变化.采用数字摄影测量、倾斜仪测量及天文实测等多种仪器和方法,研究了德令哈13.7m望远镜天线的热变形规律,并根据实时测量的主面温度分布,实现了副面自适应调焦补偿,使得天线效率提高近1倍.测量发现常规指向模型修正后的残差与天线主反射面(包括反射面板和背架,简称主面)直径方向温差存在线性相关性,故在指向解析模型中加入了温差修正项,并通过采用隔热材料包裹支腿的办法显著减小了支腿之间的温差,从而改善了望远镜的指向精度.     

德令哈13.7m望远镜谱线OTF观测系统

紫金山天文台研制的毫米波段多波束超导成像频谱接收机(简称超导成像频谱仪)于2010年底安装到13.7 m望远镜上.为发挥超导成像频谱仪的观测能力,紫金山天文台研发了基于多波束接收机的快速高效巡天的OTF(On-The-Fly)观测方法,在国际上首次提出并运用了"隔行扫描"的OTF扫描方法,对该方法进行了系统的测试和验证,并做了观测参数的优化.研发了"OTF观测星表生成器"软件,该软件提供参考点查找、观测时间估算、rms(root mean square)估算、最佳观测时段选择等功能.研发了OTF数据预处理软件,该软件具有坏数据剔除、数据修正功能,并能够结合GILDS软件完成数据网格化(Gridding)处理.通过实际观测测试,观测结果与美国五大学射电天文台(Five College Radio Astronomy Observatory,FCRAO)观测相符.该系统2011年用于13.7 m望远镜谱线成图观测,在银河画卷项目观测和其他课题成图观测中得到广泛的应用,取得了很好的观测结果,验证了该系统的有效性.     

Φ1650mm口径反射镜的坦克链支撑研究

Phi 1650mm口径反射镜是某套大口径精密光学元件检测装置中的定标校正模块, 用于对检测光路中的缩焦透镜等光学部件进行定标. 反射镜口径越大, 由于自身重力引起的变形问题越严重, 面型精度受到的影响也越大. 对于Phi 1650mm口径反射镜, 系统要求的技术指标是面型误差的均方根(Root Mean Square, RMS)小于1/70波长(波长为\lk 632.8nm). 针对这块光轴始终处于水平状态的大口径反射镜, 提出了坦克链支撑方案, 并与传统的钢带支撑做对比. 对坦克链支撑方案进行有限元分析, 逐步确定了坦克链节数和中心距, 根据标准选取了型号C2162H的双节距大滚子坦克链. 基于赫兹接触理论, 对坦克链滚子与反射镜的边缘非线性接触进行了模型简化. 经过Zernike多项式拟合后, RMS为2.58nm, 满足设计要求. 坦克链支撑结构简单、成像质量好, 同时降低了反射镜的倾覆风险, 可靠性高.     

基于小波变换的射频干扰消除方法的研究

在射电天文观测中,射频干扰(Radio Frequency Interference, RFI)会以多种形式混入望远镜接收系统,给观测带来误判或者降低观测信噪比.近年来国内国际射电天文快速发展,国内国际大型射电望远镜和阵列先后建设,观测灵敏度大为提高,射频干扰的影响尤为突出.随着科技发展和人类活动的加剧,射频干扰日益严重且不可逆转.提出利用2维离散小波变换的方法分析射电天文观测的数据,对望远镜系统输出的时间频率序列进行小波变换,根据小波系数分离出原始信号中各分量,每个分量统计得到相应的阈值,将各分量与阈值相比较识别干扰成分并标记去除.利用该方法对实际观测数据进行了处理,结果表明该方法能够很好地标记并消减干扰信号,且提高了观测的信噪比.     

30m级光学/红外望远镜的宽视场多目标光谱仪

宽视场多目标光谱仪具有宽波段、多分辨率模式和高通光效率的特点,是极大望远镜终端仪器使用率最高的通用型仪器. 30 m级望远镜的宽视场多目标光谱仪因体量和成本急剧增加而面临重要挑战,同时天文学的不断发展对天文新技术的发展提出了更高的要求,尤其是多个巡天项目对于多目标光谱后随观测的迫切需求.综述了几类宽视场多目标光谱仪的发展现状,介绍了国际3架30 m望远镜宽视场多目标光谱仪概念设计的最新进展和仪器特点,着重介绍了中国参与研制的30 m望远镜(TMT)中的宽视场多目标光谱仪的相关进展.     

伽马天文观测技术综述

伽马射线作为宇宙中极端事件的独特探针,探测伽马射线是人们了解宇宙构成、星体演化和宇宙线起源等的重要途经.伽马天文涉及了宇宙中的各种前沿科学问题并且观测所需能谱跨度极宽(102 keV–102 TeV),针对不同的科学目标和细分谱段,必须利用不同的伽马望远镜探测技术.总结了空间和地面的共5大类伽马射线观测技术,分别是编码孔径望远镜、康普顿望远镜、电子对望远镜、成像大气切伦科夫望远镜和广延大气簇射阵列;回顾了70 yr来在观测设备和技术进步的推动下伽马射线天文学领域的巨大进展,其中包含高能和甚高能谱段取得的大量成就,中低能段由于已有观测任务有限以及灵敏度低,超高能和极高能段由于观测难度大、起步时间晚,数据和成果相对其他谱段产出较少;展望了未来已经规划的伽马望远镜任务、能力及预期科学产出,其中,中低能段空间望远镜增强型ASTROGAM望远镜(e-ASTROGAM)、全天区中能伽马射线观测站(AMEGO)和甚高能段地面望远镜阵列高海拔宇宙线观测站(LHAASO)、切伦科夫望远镜阵列(CTA),由于灵敏度较同谱段已有任务灵敏度有大幅提升,极有可能在20 yr内从不同角度再度扩展人类对伽马宇宙的认知.     

光纤阵列太阳光学望远镜偏振分析器设计

给出了满足光纤阵列太阳光学望远镜(FASOT,Fibre Arrayed Solar Optical Telescope)观测目标的偏振分析器的理论设计.它具有以下特点:(1)具备偏振光学开关功能,使得高偏振测量成为可能;(2)在750nm宽度范围内,对各Stokes偏振参量都具有50%以上的理论偏振测量效率,且总的偏振测量效率高于86.6%.使得观测者在如此宽波长范围内可对多条磁敏谱线同时进行偏振测量;(3)根据所选光球和色球线侧重于对线偏振或圆偏振的测量;(4)对偏振元件的制作工艺以及安装误差等具有相当好的容忍度.以上特性使该偏振分析器成为高性能的偏振测量设备.     

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.     

The Operation of Multi-beam Receiver of Delingha 13.7 m Telescope

Delingha 13.7 m telescope is one of the most important radio telescopes in China. Since installing the superconducting spectroscopic array receiver (SSAR) and adopting the On The Fly (OTF) observation mode, the telescope has operated for nearly 10 years. During this period, a large number of astronomical observation projects have been carried out and completed, a large amount of astronomical data have been accumulated, and a series of important scientific results have been achieved. This paper introduces the operating status of SSAR in astronomical observations, the problems in operations, as well as the fault phenomena and solutions. The performance test and performance analysis of SSAR are described in detail, including the receiver noise temperature and telescope system noise temperature, image rejection ratio (IRR), receiver stability, beam performance and so on. The updating and development of SSAR are listed, including the automatic adjustment of LO (Local Oscillator) power, the updating of pre-amplification circuits of the sideband separation superconducting mixer, and the optimization of control program, etc. This paper summarizes the experiences and rules, and connects the past with the future, for applying the experiences of the maintenance and operation of SSAR to the next-generation large-scale receiver system.     

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.     

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.     

Scientific instrumentation for the 1.6 m New Solar Telescope in Big Bear

The NST (New Solar Telescope), a 1.6 m clear aperture, off‐axis telescope, is in its commissioning phase at Big Bear Solar Observatory (BBSO). It will be the most capable, largest aperture solar telescope in the US until the 4 m ATST (Advanced Technology Solar Telescope) comes on‐line late in the next decade. The NST will be outfitted with state‐of‐the‐art scientific instruments at the Nasmyth focus on the telescope floor and in the Coudé Lab beneath the telescope. At the Nasmyth focus, several filtergraphs already in routine operation have offered high spatial resolution photometry in TiO 706 nm, Hα 656 nm, G‐band 430 nm and the near infrared (NIR), with the aid of a correlation tracker and image reconstruction system. Also, a Cryogenic Infrared Spectrograph (CYRA) is being developed to supply high signal‐to‐noise‐ratio spectrometry and polarimetry spanning 1.0 to 5.0 μm. The Coudé Lab instrumentation will include Adaptive Optics (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), and Fast Imaging Solar Spectrograph (FISS). A 308 sub‐aperture (349‐actuator deformable mirror) AO system will enable nearly diffraction limited observations over the NST's principal operating wavelengths from 0.4 μm through 1.7 μm. IRIM and VIM are Fabry‐Pérot based narrow‐band tunable filters, which provide high resolution two‐dimensional spectroscopic and polarimetric imaging in the NIR and visible respectively. FISS is a collaboration between BBSO and Seoul National University focussing on chromosphere dynamics. This paper reports the up‐to‐date progress on these instruments including an overview of each instrument and details of the current state of design, integration, calibration and setup/testing on the NST (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Research on Receiver Anti-RFI of Delingha 13.7 m Telescope

In astronomical observations, the radio frequency interference (RFI) will cause pseudo spectra and reduce the reliability and validity of observational data. The RFI mitigation, which includes many technical innovations of devices and the method studies of data processing, aims at reducing the influence of RFI on the radio astronomical observation. Various efforts were made to improve the anti-RFI capability of the multi-beam receiver (Superconducting Spectroscopic Array Receiver, SSAR) of the Delingha 13.7 m telescope. The interference transmission path was analyzed. The concepts of the device RFI direct coupling coefficient and the device RFI system coupling coefficient were proposed. The proportions of interference introduced in the receiver system by the different devices were quantified, and the interference-susceptible devices in the system were located. After the anti-RFI treatment of the interference-susceptible devices, the anti-RFI capability of the receiver system is improved by 30 dB in average, and the astronomical observation efficiency of the telescope is increased by more than 10%.