Development of the Automatic Seeing Monitor for the Site Testing of Dome A

The Antarctic site-testing campaigns have shown that Dome C is an excellent astronomical site on the earth, it is better than any of existing mid-latitude astronomical sites in the world, because of its cold and dry weather, low infrared background radiation, continuously observable time as long as 3–4 months, clear and highly transparent atmosphere, low wind speed, and the absence of dust and light pollution. And in the international astronomical community it is generally believed that Dome A with a higher altitude may be better than Dome C as a potential excellent astronomical site. In the past 3 years, although held by the Center for Antarctic Astronomy of Chinese Academy of Sciences, the site testing at Dome A has preliminarily con?rmed the many advantages of Dome A as an excellent astronomical site, but the data about the atmospheric seeing, which is an important parameter for assessing the site quality for optical observations, have not been obtained until now. Hence, on the basis of a commercial telescope with the diameter of 35 cm, we have made the hardware reformation and software development to have it operate as a DIMM (Differential Image Motion Monitor), which can simultaneously monitor both the seeing and isoplanatic angle at Dome A automatically. At present this instrument has been shipped to Antarctica by the “Xuelong” exploration ship, and will be installed at Dome A, and begin to work in early 2011. Before the shipment, by through the comparative measurements together with an existing seeing monitor at the Xinglong astronomical station, the software, hardware, as well as the installation and adjustment of the instrument, are further veri?ed by testing.     

南极冰穹A首台自动视宁度检测仪的研制

南极冰穹C (Dome C)的选址结果显示:Dome C具有寒冷干燥、红外背景辐射低、可连续3～4个月观测、空气明净、透过率高、风速低等特征,是比地面上任何中纬度台址都好的天文观测台址.而由我国最先登陆的内陆最高点冰穹A (Dome A)被国际天文界广泛认为可能是比Dome C更好的天文台址.近3 yr来,中国科学院南极天文中心领导开展Dome A的台址测量工作,初步结果表明Dome A作为天文台址具有巨大优势.但是到目前还没有获得直接用于衡量天文台址在光学观测方面的主要参数—视宁度数据.介绍了中国科学院南京天文光学技术研究所自行研制的我国首个用于Dome A的自动视宁度测量仪,基于一台口径35 cm的商用望远镜进行硬件改造和软件开发,使其能在Dome A低温低压环境下进行自动观测和数据处理.目前该仪器已随“雪龙号,科考船起运南极,于2011年初安装到Dome A并开始测量.起运前,在兴隆观测站与中国科学院国家天文台(国台)选址组的一台视宁度监测仪进行了对比测量,对软件、硬件和装调方法进行了检验验证.     

Enhanced remote astronomical archive system based on the file-level Unlimited Sliding-Window technique

Data archiving is one of the most critical issues for modern astronomical observations. With the development of a new generation of radio telescopes, the transfer and archiving of massive remote data have become urgent problems to be solved. Herein, we present a practical and robust file-level flow-control approach, called the Unlimited Sliding-Window(USW), by referring to the classic flow-control method in the TCP protocol. Based on the USW and the Next Generation Archive System(NGAS) developed for the Murchison Widefield Array telescope, we further implemented an enhanced archive system(ENGAS)using ZeroMQ middleware. The ENGAS substantially improves the transfer performance and ensures the integrity of transferred files. In the tests, the ENGAS is approximately three to twelve times faster than the NGAS and can fully utilize the bandwidth of network links. Thus, for archiving radio observation data, the ENGAS reduces the communication time, improves the bandwidth utilization, and solves the remote synchronous archiving of data from observatories such as Mingantu spectral radioheliograph. It also provides a better reference for the future construction of the Square Kilometer Array(SKA) Science Regional Center.     

Telescope and instrument robotization at Dome C

This article reviews the situation for robotization of telescopes and instruments at the Antarctic station Concordia on Dome C. A brain‐storming meeting was held in Tenerife in March 2007 from which this review emerged.We describe and summarize the challenges for night‐time operations of various astronomical experiments at conditions “between Earth and Space” and conclude that robotization is likely a prerequisite for continuous astronomical data taking during the 2000‐hour night at Dome C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Design of a multi-function high-speed digital baseband data acquisition system

A multi-function digital baseband data acquisition system is designed for the sampling,distribution and recording of wide-band multi-channel astronomical signals.The system hires a SNAP2board as a digital baseband converter to digitize,channelize and packetize the received signal.It can be configured dynamically from a single channel to eight channels with a maximum bandwidth of 4096 MHz.Eight parallel HASHPIPE instances run on four servers,each carrying two NVMe SSD cards,achieving a total continuous write rate of 8 GB s~(-1).Data are recorded in the standard VDIF file format.The system is deployed on a 25-meter radio telescope to verify its functionality based on pulsar observations.Our results indicate that during the 30-minute observation period,the system achieved zero data loss at a data recording rate of 1 GB s~(-1)on a single server.The system will serve as a verification platform for testing the functions of the QTT (Qi Tai radio Telescope) digital backend system.In addition,it can be used as a baseband/VLBI(Very Long Baseline Interferometry) recorder or D-F-engine of correlator/beamformer as well.     

南极洲高原介绍

南极洲高原的天文开发在过去的10年中有了显著的进展．大的天文设施已在南极(South Pole)的Amundsen-Scott站运行,更具威力的望远镜已在计划或正在那儿建设,然而由于一些重要的原因,高原站址冰穹A(Dome A)和冰穹C(Dome C)对多种天文学科似乎比南极更具有利条件．2005年1月中国对冰穹A的成功考察,加上2005年以整年运行为目的的法/意Concordia站在冰穹C的开启,已为南极洲天文学创造了激动人心的新机遇．     

Comparison of the atmosphere above the South Pole, Dome C and Dome A: first attempt

The atmospheric properties above three sites (Dome C, Dome A and the South Pole) on the Internal Antarctic Plateau are investigated for astronomical applications using the monthly median of the analyses from ECMWF (the European Centre for Medium-Range Weather Forecasts). Radiosoundings extended on a yearly time-scale at the South Pole and Dome C are used to quantify the reliability of the ECMWF analyses in the free atmosphere as well as in the boundary and surface layers, and to characterize the median wind speed in the first 100 m above the two sites. Thermodynamic instability properties in the free atmosphere above the three sites are quantified with monthly median values of the Richardson number. We find that the probability to trigger thermodynamic instabilities above 100 m is smaller on the Internal Antarctic Plateau than on mid-latitude sites. In spite of the generally more stable atmospheric conditions of the Antarctic sites compared to mid-latitude sites, Dome C shows worse thermodynamic instability conditions than those predicted above the South Pole and Dome A above 100 m. A rank of the Antarctic sites done with respect to the strength of the wind speed in the free atmosphere (ECMWF analyses) as well as the wind shear in the surface layer (radiosoundings) is presented.     

Astronomical image data compression by morphological skeleton transformation

Astronomical instruments currently provide a large amount of data. Nowadays, a large part of these data are image frames obtained with receivers of increasing size. The scan of large astronomical plates using fast microdensitometers gives image frames of over 30000×30000 pixels. More and more often, images are transmitted over a network in order to control the observations, to process the data, and to examine or to fill a data bank. The time taken for archiving, the cost of communication, the available memory given by magnetic tapes, and the limited bandwidth of transmission lines are reasons which lead us to examine the data compression of astronomical images.The astronomical image has the characteristic of being a set of astronomical sources in the sky background whose values are not zero. We are, in fact, only interested in the astronomical sources. Once a suitable detection is made, we generally want a compression without any distorsion. In this paper, we present a method which can be adapted for this purpose. It is based on morphological skeleton transformations. The experimental results show that it can give us an efficient compression. Moreover, the flexibility of choosing a structure element adapted to different images and the simplicity of implementation are other advantages of this method. Because of these characteristics, different compression applications may be treated.     

Astronomy from Dome A in Antarctica

Dome A in Antarctica has been demonstrated to be the best site on earth for optical, infrared, and terahertz astronomical observations by more and more evidence, such as excellent free-atmosphere seeing,extremely low perceptible water vapor, low sky background, and continuous dark time, etc. In this paper,we present a complete picture of the development of astronomy at Dome A from the very beginning, review recent progress in time-domain astronomy, demonstrate exciting results of the site testing, and address the challenges in instrumentation. Currently proposed projects are briefly discussed.     

Enhanced management of personal astronomical data with FITSManager

Although the roles of data centers and computing centers are becoming more and more important, and on-line research is becoming the mainstream for astronomy, individual research based on locally hosted data is still very common. With the increase of personal storage capacity, it is easy to find hundreds to thousands of FITS files in the personal computer of an astrophysicist. Because Flexible Image Transport System (FITS) is a professional data format initiated by astronomers and used mainly in the small community, data management toolkits for FITS files are very few. Astronomers need a powerful tool to help them manage their local astronomical data. Although Virtual Observatory (VO) is a network oriented astronomical research environment, its applications and related technologies provide useful solutions to enhance the management and utilization of astronomical data hosted in an astronomer’s personal computer. FITSManager is such a tool to provide astronomers an efficient management and utilization of their local data, bringing VO to astronomers in a seamless and transparent way. FITSManager provides fruitful functions for FITS file management, like thumbnail, preview, type dependent icons, header keyword indexing and search, collaborated working with other tools and on-line services, and so on. The development of the FITSManager is an effort to fill the gap between management and analysis of astronomical data.     

EfficientNetV2-S-Triplet7: 一种改进的星系newline 形态学分类算法

星系的形态与星系的形成和演化息息相关, 其形态学分类是星系天文学后续研究的重要一环. 当前海量天文观测数据的出现使得天文数据自动分析方法越来越得到重视, 针对此问题, 利用先进的深度学习骨干网络EfficientNetV2, 分析不同的注意力机制类型和使用节点对网络性能的影响, 构建了一种命名为EfficientNetV2-S-Triplet7 (即在EfficientNetV2-S stage7的$1\times1$卷积层后加入Triplet模块)的改进算法模型来实现星系形态学的自动分类. 使用第二期星系动物园(Galaxy Zoo 2, GZ2)中超过24万张的测光图像作为初始数据进行实验测试. 在对数据进行预处理时采取了尺寸抖动、翻转、色彩畸变等图像增强手段来解决图像数量的不平衡问题. 在同一系列经典和前沿的深度学习算法模型AlexNet、ResNet-34、MobileNetV2、RegNet进行对比实验后, 得出EfficientNetV2-S-Triplet7算法在分类准确率、查全率和F1分数等指标上具有最好的测试结果. 在9375张测试图像中的3项指标值分别可达到89.03%、90.21%、89.93%, 查准率达到89.69%, 在其他模型中排在第3位. 该结果表明将EfficientNetV2-S-Triplet7算法应用于大规模星系数据的形态学分类任务中有很好的效果.     

中国频谱射电日像仪FITS-IDI文件格式研究

我国新一代中国频谱射电日像仪（Chinese Spectral Radio Heliograph,CSRH）原始观测数据采用自定义格式,在进行后续处理与共享使用时必须转换相应的格式.在分析FITS-IDI（FITS Interferometry Data Interchange）格式的基础上,结合CSRH的实际观测模式与数据产出方式,定义与设计了符合项目情况的FITS-IDI格式及字段,并对FITS-IDI文件中若干字段的值如何获取、计算进行了深入讨论.根据定义生成的FITS-IDI文件已成功导入CASA软件,并可以进行后续处理.经过对CASA测量集文件的核实,证明了数据生成的正确性.本研究有效地推进了CSRH的建设工作,也对其他射电干涉阵数据存储有一定的参考价值.     

快速射电暴观测数据干扰缓解方法研究

从海量的天文观测数据中快速搜寻罕见的快速射电暴(Fast Radio Burst, FRB)事件, 干扰缓解是其中一项关键而具有挑战的工作. 射频干扰(Radio Frequency Interference, RFI)会淹没真实的天文事件, 还会导致搜寻管线输出大量的假阳性候选体. 由于干扰来源及其种类的复杂性, 目前并没有一种通用的方法可以解决这个问题. 为了降低干扰对FRB观测搜寻的影响, 分析和研究了南山26m射电望远镜L波段观测数据中的干扰情况, 针对主要的窄带干扰和宽带干扰建立了3层次的干扰缓解处理流程, 从而有效缓解了观测数据的干扰污染情况. 将该流程嵌入到FRB色散动态谱搜寻(Dispersed Dynamic Spectra Search, DDSS)管线中, 实验结果表明, 搜寻管线的检测率和检测精度得到了进一步的提高. 该方法为FRB观测数据干扰缓解处理提供了有价值的参考.     

IERS数据动态提取与更新系统的设计与实现

在高精度的位置计算中需要获取计算时刻所在日期的闰秒,以及UT1-UTC等关键数据,但长期以来这一类数据的维护均是手工进行,出错率高.针对新一代中国太阳射电日像仪观测与数据处理过程中的位置计算需要,实现了一个自动提取国际地球自转服务（IERS）参数的数据更新自维护子系统.系统可以根据需要自动运行、自动下载并分拆IERS网站数据,采用正则表达式从文本中自动获取所需要的实测值与预报值,自动在本地构建一个2004年12月31日以来的IERS数据库,并根据每周所获得的数据维护整个IERS的数据,将最新的实测值与预报值存入数据文件,实现了数据的滚动更新.系统彻底解决了手工维护数据的问题,为中国太阳射电日像仪的自动数据处理流水线打下了较好的基础.同时,本文提出的方法是一种通用的方法,可以方便地集成应用到国内其它天文位置计算领域.     

The OH Maser Line Receiving System for the Urumqi 25m Radio Telescope

A maser spectral line system is newly implemented on the Urumqi 25m Radio Telescope. The system consists mainly of a cooling receiver and a 4096 channels digital correlation spectrometer. The frequency resolution of the spectrometer at the maximum signal bandwidth of 80MHz is 19.5kHz. After careful calibrations observation at the 1665 MHz OH maser emission was made towards a number of sources, including W49N and W75N. The observed results demonstrate that the digital correlation spectrometer is suitable for astronomical spectral line observations.     

基于ASCOM标准的天文电动调焦器设计

随着天文技术的不断发展,远程观测和自主观测逐渐成为天文观测的主流趋势,自动调焦技术也越来越受到重视。电动调焦器是天文望远镜不可或缺的附属设备,是实现自动调焦的关键设备。为实现云南天文台丽江观测站10英寸米德望远镜的自动调焦,自行研发了一套天文电动调焦器,设计相关控制电路,制定串口通信协议,并编写了一套开源天文公共对象模型(Astronomy Common Object Model,ASCOM)驱动程序SS Focuser,详细介绍了该电动调焦器的结构原理和实现方法,实测结果表明,电动调焦器具有很好的稳定性,完全满足设计要求,为天文电动调焦器设计提供了可借鉴的经验和方法。     

实时控制时钟的几种设计方法

介绍了3种在天文观测中用于实时控制、实时数据采集的时钟设计方法,比较了硬件制作的难易程度。