共查询到19条相似文献，搜索用时 156 毫秒
1.
平方公里阵列(Square Kilometre Array,SKA)项目是建设全球最大射电望远镜的国际合作项目,其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级.连续谱巡天是SKA的主要观测模式之一,基于连续谱成像建立巡天区域的标准星图,将能为后续天文科学研究奠定重要基础.银河系与河外星系全天默奇森宽场阵列拓展巡天(GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended,GLEAM-X)是2018—2020年利用SKA先导望远镜默奇森宽场阵列(Murchison Wide-field Array,MWA)二期拓展阵列开展的新的射电连续谱巡天项目,观测期间积累了大量的低频巡天观测数据.海量观测数据的自动化、大批量处理是SKA望远镜项目所面临的的最大挑战和难题之一,基于分布式执行框架的成像管线优化经验将有助于解决海量数据处理问题.详细介绍了GLEAM-X成像管线并对其进行整合和改进,在中国SKA区域中心原型机(China SKA Regional Centre Prototype,... 相似文献
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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. 相似文献
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为了开展雷达天文科学研究, 将射电望远镜接收的雷达回波信号进行采集和记录, 研究基于SNAP (Smart Network ADC (Analog to Digital Converter) Processor)硬件实验板和快速存储服务器设计并开发了雷达天文基带数据采集与记录系统. 该系统采用CASPER (Collaboration for Astronomy Signal Processing and Electronics Research)提供的图形化FPGA (Field Programmable Gate Array)开发工具流, 设计了双通道、256MHz带宽信号采集和VDIF (VLBI (Very Long Baseline Interferometry) Data Interchange Format)基带数据输出固件程序; 基于HASHPIPE (High Availability SHared PIPeline Engine)多线程管理引擎开发了双万兆以太网口实时基带数据存储程序, 存储带宽达到1GB/s; 最后编写了VDIF格式到雷达天文格式的转换程序. 经过脉冲星信号观测实验检测, 该系统准确、可靠. 相似文献
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为了方便国内学者对脉动变星进行研究,建立了一个数据库,目前包含了时间长达10 yr左右的巡天项目MAssive Compact Halo Objects(大质量致密银晕天体,MACHO)和Optical Gravitational Lensing Experiment(光学引力透镜实验,OGLE)发现的脉动变星,一共容纳了来自银河系核球与大小麦哲伦云中的共近23万颗变星.采用的软件是LAMP,即Linux+Apache+MySQL+PHP.数据库的使用通过网页的简单搜索界面实现,搜索参数主要是天体的赤经、赤纬和半径.鉴于本数据库的灵活性,将来很方便加入其他的变星数据. 相似文献
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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. 相似文献
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为解决常规射电望远镜归心测量工作耗时耗力的问题,引入GNSS (Global Navigation Satellite System)同步监测技术实现了一种针对射电望远镜参考点的无人值守监测方法.设计了针对GNSS靶标点观测数据的归算方法,包括数据匹配、数据检核以及后续精度评估等步骤,并对2018年佘山25-m射电VLBI (Very Long Baseline Interferometry)望远镜的GNSS靶标点实测数据开展了数据预处理、解析与归心解算等,证明了该方法的可行性.结果表明基于该方法,采用单日内部分(5%)数据(约7600个靶标点),所测定的VLBI望远镜参考点的点位形式精度可达3 mm.总结了针对射电望远镜采用GNSS开展无人值守归心测量先行试验中的一些经验教训,明确了利用该方法测量过程中应该注意的问题,为今后更高精度射电望远镜参考点无人值守归心监测提供重要参考. 相似文献
7.
天体光谱分类是天文学研究的重要内容之一,其关键是从光谱数据中选择和提取对分类识别最有效的特征构建特征空间.提出一种新的基于2维傅里叶谱图像的特征提取方法,并应用于LAMOST (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope)恒星光谱数据的分类研究中.光谱数据来源于LAMOST Data Release 5(DR5),选取30000条F、 G和K型星光谱数据,利用短时傅里叶变换(Short-Time Fourier Transform, STFT)将1维光谱数据变换成2维傅里叶谱图像,对得到的2维傅里叶谱图像采用深度卷积网络模型进行分类,得到的分类准确率是92.90%.实验结果表明通过对LAMOST恒星光谱数据进行STFT可得到光谱的2维傅里叶谱图像,谱图像构成了新的光谱数据特征和特征空间,新的特征对于光谱数据分类是有效的.此方法是对光谱分类的一种全新尝试,对海量天体光谱的分类和挖掘处理有一定的开创意义. 相似文献
8.
随着快速射电暴(Fast Radio Burst, FRB)及旋转射电暂现源(Rotating Radio Transient, RRAT)等一些没有明显周期的天体被发现以来,单脉冲搜索受到研究人员广泛关注。同时随着射电望远镜设备日趋完善,更高分辨率和更广阔的观测空间产生的观测数据量剧增,观测数据的快速处理迫在眉睫。介绍了PRESTO(PulsaR Exploration and Search TOolkit)中单脉冲搜索,使用Cython编程方式对单脉冲搜索中去趋势(Detrend)算法进行优化,并通过Ray框架实现单脉冲搜索在中央处理器(Central Processing Units, CPU)上并行化。实验结果表明,算法优化后的单脉冲搜索并行化,能明显提升搜索程序性能,显著缩短数据处理时间,同时该并行策略仅基于中央处理器,无需修改代码即可在纯中央处理器环境下实现高性能数据处理。 相似文献
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针对大口径、高性能射电望远镜天线受到的随机及时变风扰的问题, 利用自回归滑动平均模型预测望远镜周围风速, 提前计算风致结构变形量, 同时为望远镜伺服控制系统提供足够执行时间来降低风扰影响. 基于新疆奇台110m口径全向可动射电望远镜(QiTai Telescope, QTT)台址风场数据特征, 通过赤池信息准则和贝叶斯信息准则辨识模型阶次, 利用最大似然法估计模型参数, 分析模型残差特性以检验自回归滑动平均模型的有效性. 通过计算不同季度预测数据与测试数据偏差得到预测模型的精度, 夏季平均绝对误差为0.133mcdots-1, 秋季平均绝对误差为0.162mcdots-1, 冬季平均绝对误差为0.287mcdots-1. 整体来看, 基于QTT台址不同季度风速数据建立的自回归滑动平均模型预测误差较小, 满足射电望远镜风扰控制系统的需求, 能为大口径射电望远镜风扰控制提供必要数据支撑. 相似文献
11.
张利 Li-Gong Mi Long Xu Ming Zhang Dan-Yang Li Xiang Liu Feng Wang Yi-Fan Xiao Zhong-Zu Wu 《天文和天体物理学研究(英文版)》2021,(3):117-127
A sky model from CLEAN deconvolution is a particularly effective high dynamic range reconstruction in radio astronomy,which can effectively model the sky and remove the sidelobes of the point spread function(PSF)caused by incomplete sampling in the spatial frequency domain.Compared to scale-free and multi-scale sky models,adaptive-scale sky modeling,which can model both compact and diffuse features,has been proven to have better sky modeling capabilities in narrowband simulated data,especially for large-scale features in high-sensitivity observations which are exactly one of the challenges of data processing for the Square Kilometre Array(SKA).However,adaptive scale CLEAN algorithms have not been verified by real observation data and allow negative components in the model.In this paper,we propose an adaptive scale model algorithm with non-negative constraint and wideband imaging capacities,and it is applied to simulated SKA data and real observation data from the Karl G.Jansky Very Large Array(JVLA),an SKA precursor.Experiments show that the new algorithm can reconstruct more physical models with rich details.This work is a step forward for future SKA image reconstruction and developing SKA imaging pipelines. 相似文献
12.
We present a study of the dynamic range limitations in images produced with the proposed Square Kilometre Array (SKA) using
the Cotton-Schwab CLEAN algorithm for data processing. The study is limited to the case of a small field of view and a snap-shot observation. A new
modification of the Cotton-Schwab algorithm involving optimization of the position of clean components is suggested. This
algorithm can reach a dynamic range as high as 106 even if the point source lies between image grid points, in contrast to about 103 for existing CLEAN-based algorithms in the same circumstances. It is shown that the positional accuracy of clean components, floating point
precision and the w-term are extremely important at high dynamic range. The influence of these factors can be reduced if the variance of the
gradient of the point spread function is minimized during the array design. 相似文献
13.
M. Massardi A. Lapi G. De Zotti R. D. Ekers L. Danese 《Monthly notices of the Royal Astronomical Society》2008,384(2):701-710
In the standard galaxy formation scenario plasma clouds with a high thermal energy content must exist at high redshifts since the protogalactic gas is shock heated to the virial temperature, and extensive cooling, leading to efficient star formation, must await the collapse of massive haloes (as indicated by the massive body of evidence, referred to as downsizing ). Massive plasma clouds are potentially observable through the thermal and kinetic Sunyaev–Zel'dovich effects and their free–free emission. We find that the detection of substantial numbers of galaxy-scale thermal Sunyaev–Zel'dovich signals is achievable by blind surveys with next generation radio telescope arrays such as EVLA, ALMA and SKA. This population is even detectable with the 10 per cent SKA, and wide field of view options at high frequency on any of these arrays would greatly increase survey speed. An analysis of confusion effects and of the contamination by radio and dust emissions shows that the optimal frequencies are those in the range 10–35 GHz. Predictions for the redshift distributions of detected sources are also worked out. 相似文献
14.
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. 相似文献
15.
《Chinese Astronomy and Astrophysics》2019,43(3):424-443
The uv-faceting imaging is one of the widely used large field of view imaging technologies, and will be adopted for the data processing of the low-frequency array in the first stage of the Square Kilometre Array (SKA1). Due to the scale of the raw data of SKA1 is unprecedentedly large, the efficiency of data processing directly using the original uv-faceting imaging will be very low. Therefore, a uv-faceting imaging algorithm based on the MPI (Message Passing Interface)+OpenMP (Open Multi-Processing) and a uv-faceting imaging algorithm based on the MPI+CUDA (Compute Unified Device Architecture) are proposed. The most time-consuming data reading and gridding in the algorithm are optimized in parallel. The verification results show that the results of the proposed two algorithms are basically consistent with that obtained by the current mainstream data processing software CASA (Common Astronomy Software Applications), which indicates that the proposed two algorithms are basically correct. Further analysis of the accuracy and total running time shows that the MPI+CUDA method is better than the MPI+OpenMP method in both the correctness rate and running speed. The performance test results show that the proposed algorithms are effective and have certain extensibility. 相似文献
16.
Lao Bao-qiang An Tao Chen Xiao Wu Xiao-cong Lu Yang 《Chinese Astronomy and Astrophysics》2018,42(4):626-651
Wide-field imaging of low-frequency radio telescopes is subject to a number of difficult problems. One particularly pernicious problem is the non-coplanar baseline effect. It will lead to distortion of the final image when the phase of -direction called -term is ignored. The image degradation effects are amplified for the telescopes with a wide field of view. This paper summarizes and analyzes several -term correction methods and their technical principles. Their advantages and disadvantages are analyzed after comparing their computational cost and computational complexity. We conduct simulations with two of these methods, i.e., faceting and -projection, based on the configuration of the first-phase Square Kilometre Array (SKA) low-frequency array. The resulted images are also compared with the result of the two-dimensional Fourier transform method. The results show that the image quality and correctness derived from both faceting and -projection are better than the two-dimensional Fourier transform method in wide-field imaging. The effects of the number of facets and the -direction step length on the image quality and running time are evaluated. The results indicate that the number of facets and the -direction step length must be reasonable. Finally, we analyze the effect of data size on the running times of the faceting and -projection algorithms. The results show that the faceting and -projection algorithms need to be optimized before the huge amount of data processing. The research of the present paper initiates the analysis of wide-field imaging techniques and their applications in the existing and future low-frequency arrays, and will foster their applications in even broader fields. 相似文献
17.
The performance goals of the Square Kilometre Array (SKA) are such that major departures from prior practice for imaging interferometer arrays are required. One class of solutions involves the construction of large numbers of stations, each composed of one or more small antennas. The advantages of such a “large-N” approach are already documented, but attention has recently been drawn to scaling relationships for SKA data processing that imply excessive computing costs associated with the use of small antennas. In this paper we examine the assumptions that lead to such scaling laws, and argue that in general they are unlikely to apply to the SKA situation. A variety of strategies for SKA imaging which exhibit better scaling behaviour are discussed. Particular attention is drawn to field of view issues, and the possibility of using weighting functions within an advanced correlator system to precisely control the field-of-view. 相似文献
18.
Steven W. Ellingson 《Experimental Astronomy》2004,17(1-3):261-267
Radio frequency interference (RFI) has plagued radio astronomy from its inception. The Workshop on the Mitigation of Radio Frequency Interference in Radio Astronomy (RFI2004) was held in Penticton, BC, Canada in July 2004 in order to consider the prognosis for the RFI problem, in particular as it impacts the planned Square Kilometre Array (SKA). This paper concludes that RFI is unlikely to be a “showstopper” in achieving SKA science goals, but that improved RFI mitigation technology may nevertheless be essential in order to take advantage of the vastly improved sensitivity, bandwidth, and field of view. Reported results provide some optimism that the desired improvements in RFI mitigation technology are possible, but indicate that much more work is required. 相似文献
19.
《天文和天体物理学研究(英文版)》2021,(4)
The Square Kilometre Array(SKA) would be the world's largest radio telescope with eventually over a square kilometre of collecting area.However,there are enormous challenges in its data processing.The use of modern distributed computing techniques to solve the problem of massive data processing in the SKA is one of the most important challenges.In this study,basing on the Dask distribution computational framework,and taking the visibility function integral processing as an example,we adopt a multi-level parallelism method to implement distributed averaging over time and channel.Dask Array was used to implement super large matrix or arrays with supported parallelism.To maximize the usage of memory,we further exploit the data parallelism provided by Dask that intelligently distributes the computational load across a network of computer agents and has a built-in fault tolerance mechanism.The validity of the proposed pattern was also verified by using the Common Astronomy Software Application(CASA),wherein we analyze the smearing effects on images reconstructed from different resolution visibilities. 相似文献