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HiFAST: An H I Data Calibration and Imaging Pipeline for FAST.Ⅲ.Standing Wave Removal

Research in Astronomy and Astrophysics 2025年第1期25卷 249-263页

作者： Chen Xu Jie Wang Yingjie Jing Fujia Li Hengqian Gan Ziming Liu Tiantian Liang Qingze Chen Zerui Liu Zhipeng Hou Hao Hu Huijie Hu Shijie Huang Peng Jiang Chuan-Peng Zhang Yan Zhu National Astronomical Observatories Chinese Academy of Sciences School of Astronomy and Space Science University of Chinese Academy of Sciences Institute for Frontiers in Astronomy and Astrophysics Beijing Normal University Department of Astronomy University of Science and Technology of China School of Astronomy and Space Science University of Science and Technology of China CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of Sciences Guizhou Radio Astronomical Observatory Guizhou University

The standing waves existing in radio telescope data are primarily due to reflections among the instruments,which significantly impact the spectral quality of the Five-hundred-meter Aperture Spherical radio Telescope (FAST).Eliminating these standing waves for FAST is challenging given the constant changes in their phases and *** a ten-second period,the phases shift by 18°while the amplitudes fluctuate by 6 m ***,we developed the fast Fourier transform (FFT) filter method to eliminate these standing waves for every individual *** FFT filter can decrease the rms from 3.2 to 1.15 times the theoretical *** to other methods such as sine fitting and running median,the FFT filter achieves a median rms of approximately 1.2 times the theoretical expectation and the smallest scatter at 12%.Additionally,the FFT filter method avoids the flux loss issue encountered with some other *** FFT is also efficient in detecting harmonic radio frequency interference (RFI).In the FAST data,we identified three distinct types of harmonic RFI,each with amplitudes exceeding 100 m K and intrinsic frequency periods of 8.1,0.5,and 0.37 MHz,*** FFT filter,proven as the most effective method,is integrated into the H I data calibration and imaging pipeline for FAST (Hi FAST,https://***).

关键词： methods:data analysis techniques:image processing galaxies:ISM radio lines:galaxies

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Study on Real-time Monitoring Method for Dust-scattered Stray Light in the Spectral Imaging CoronaGraph of the Chinese Meridian Project Phase Ⅱ

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Research in Astronomy and Astrophysics 2025年第1期25卷 297-308页

作者： Da-Yang Liu Xiao-Yu Yu Hong-Xin Zhang Zheng-Hua Huang Li-Dong Xia Ming-Zhe Sun Xian-Liang Mao Bo-Yu Sun Ning Tang Hui Fu Wei-Xin Liu Chao Zhang Jian-Ping Han Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong University Changchun institute of Optics Fine Mechanics and PhysicsChinese Academy of Sciences

The dust-scattered stray light in an inner-occulted coronagraph mainly arises from dust particles on the surfaces of the objective *** to the random accumulation of dust on the lens surfaces,it is challenging to monitor this type of stray light and no application can be used for its real-time monitor in the *** this study,we provide a system and method to overcome this issue,and these have been applied to the Spectral Imaging CoronaGraph (SICG) of the Chinese Meridian *** method is based on the relation between the sizes of dust particles and its stray light level at the imaging plane established in the laboratory and the relation between the real size of dust particles and the occupancies on the imaging *** monitor the stray light levels accounted for by dusts,one needs only an image of the objective lens that can be provided by the auxiliary imaging system that specially comes with *** tests show that the errors of the method are less or about 2%,giving a strong confidence in its *** provides a handy tool to monitor the dust level of the objective lens of SICG and has significantly improved the efficiency of the pipeline of stray light control.

关键词： Sun:corona techniques:image processing instrumentation:miscellaneous methods:analytical scattering

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Resolution Enhancement of SOHO/MDI Magnetograms

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Research in Astronomy and Astrophysics 2024年第6期24卷 358-367页

作者： Ying Qin Kai-Fan Ji Hui Liu Xiao-Guang Yu Yunnan Observatories Chinese Academy of SciencesKunming 650011China University of Chinese Academy of Sciences Beijing 100049China Yunnan Key Laboratory of Solar Physics and Space Science Kunming 650216China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of SciencesKunming 650216China

Research on the solar magnetic field and its effects on solar dynamo mechanisms and space weather events has benefited from the continual improvements in instrument resolution and measurement *** augmentation and assimilation of historical observational data timelines also play a significant role in understanding the patterns of solar magnetic field *** the realm of astronomical data processing,super-resolution(SR)reconstruction refers to the process of using a substantial corpus of training data to learn the nonlinear mapping between low-resolution(LR)and high-resolution(HR)images,thereby achieving higherresolution astronomical *** paper is an application study in high-dimensional nonlinear *** learning models were employed to perform SR modeling on SOHO/MDI magnetograms and SDO/HMI magnetograms,thus reliably achieving resolution enhancement of full-disk SOHO/MDI magnetograms and enhancing the image resolution to obtain more detailed *** this study,a data set comprising 9717pairs of data from 2010 April to 2011 February was used as the training set,1332 pairs from 2011 March were used as the validation set and 1034 pairs from 2011 April were used as the test *** data preprocessing,we randomly cropped 128×128 sub-images as the LR cases from the full-disk MDI magnetograms,and the corresponding 512×512 sub-images as HR ones from the HMI full-disk magnetograms for model *** tests conducted have shown that the study successfully produced reliable 4×SR reconstruction of full-disk MDI *** MESR model's results(0.911)were highly correlated with the target HMI magnetographs as indicated by the correlation coefficient ***,the method achieved the best PSNR,SSIM,MAE and RMSE values,indicating that the MESR model can effectively reconstruct magnetograms.

关键词： magnetic fields techniques:image processing virtual observatory tools Sun:magnetic fields

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A Region Selection Method for Real-time Local Correlation Tracking of Solar Full-disk Magnetographs

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Research in Astronomy and Astrophysics 2022年第9期22卷 106-115页

作者： Yang Bai Jia-Ben Lin Xian-Yong Bai Xiao Yang Dong-Guang Wang Yuan-Yong Deng Xiao-Ming Zhu Xing Hu Wei Huang Li-Yue Tong Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Hundreds of images with the same polarization state are first registered to compensate for the jitters during an observation and then integrated to realize the needed spatial resolution and sensitivity for solar magnetic field measurement. Due to the feature dependent properties of the correlation tracker technique, an effective method to select the feature region is critical for low-resolution full-disk solar filtergrams, especially those with less significant features when the Sun is quiet. In this paper, we propose a region extraction method based on a Hessian matrix and information entropy constraints for local correlation tracking(CT) to get linear displacement between different images. The method is composed of three steps:(1) extract feature points with the Hessian matrix,(2)select good feature points with scale spaces and thresholds, and(3) locate the feature region with the twodimensional information entropy constraints. Both the simulated and observational experiments demonstrated that our region selection method can efficiently detect the linear displacement and improve the quality of a groundbased full-disk solar magnetogram. The local CT with the selected regions can obtain displacement detection results as good as the global CT and at the same time significantly reduce the average calculation time.

关键词： Sun:photosphere Sun:magnetic fields techniques:image processing

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A novel approach to visibility-space modelling of interferometric gravitational lens observations at high angular resolution

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MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 2021年第1期501卷 515-530页

作者： Powell, Devon Vegetti, Simona McKean, John P. Spingola, Cristiana Rizzo, Francesca Stacey, Hannah R. Max Planck Inst Astrophys Karl Schwarzschild Str 1 D-85748 Garching Germany Univ Groningen Kapteyn Astron Inst POB 800 NL-9700 AV Groningen Netherlands Netherlands Inst Radio Astron ASTRON POB 2 NL-7990 AA Dwingeloo Netherlands INAF Ist Radioastron Via Gobetti 101 I-40129 Bologna Italy Univ Bologna Dipartimento Fis & Astron Via Gobetti 93-2 I-40129 Bologna Italy

We present a new gravitational lens modelling technique designed to model high-resolution interferometric observations with large numbers of visibilities without the need to pre-average the data in time or frequency. We demonstrate the accuracy of the method using validation tests on mock observations. Using small data sets with similar to 10(3) visibilities, we first compare our approach with the more traditional direct Fourier transform (DFT) implementation and direct linear solver. Our tests indicate that our source inversion is indistinguishable from that of the DFT. Our method also infers lens parameters to within 1 to 2 per cent of both the ground truth and DFT, given sufficiently high signal-to-noise ratio (SNR). When the SNR is as low as 5, both approaches lead to errors of several tens of per cent in the lens parameters and a severely disrupted source structure, indicating that this is related to the SNR and choice of priors rather than the modelling technique itself. We then analyse a large data set with similar to 10(8) visibilities and a SNR matching real global Very Long Baseline Interferometry observations of the gravitational lens system MG J0751+2716. The size of the data is such that it cannot be modelled with traditional implementations. Using our novel technique, we find that we can infer the lens parameters and the source brightness distribution, respectively, with an RMS error of 0.25 and 0.97 per cent relative to the ground truth.

关键词： gravitational lensing: strong methods: data analysis techniques: high angular resolution techniques:image processing

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Automatic removal of false image stars in disk-resolved images of the Cassini Imaging Science Subsystem

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Research in Astronomy and Astrophysics 2020年第7期20卷 93-102页

作者： Qing-Feng Zhang Zhi-Cong Lu Xiao-Mei Zhou Yang Zheng Zhan Li Qing-Yu Peng Shun Long Wei-Heng Zhu Department of Computer Science Jinan UniversityGuangzhou 510632China Sino-French Joint Laboratory for Astrometry Dynamics and Space ScienceJinan UniversityGuangzhou 510632China

Taking a large number of images,the Cassini Imaging Science Subsystem(ISS)has been routinely used in *** ISS images,disk-resolved objects often lead to false detection of stars that disturb the camera pointing *** aim of this study was to develop an automated processing method to remove the false image stars in disk-resolved objects in ISS *** method included the following steps:extracting edges,segmenting boundary arcs,fitting circles and excluding false image *** proposed method was tested using 200 ISS *** experimental results show that it can remove the false image stars in more than 95%of ISS images with disk-resolved objects in a fully automatic manner,i.e.,outperforming the traditional circle detection based on Circular Hough Transform(CHT)by 17%.In addition,its speed is more than twice as fast as that of the CHT *** is also more robust(no manual parameter tuning is needed)when compared with *** proposed method was also applied to a set of ISS images of Rhea to eliminate the mismatch in pointing correction in automatic *** results showed that the precision of final astrometry results can be improve by roughly 2 times that of automatic procedure without the *** proved that the proposed method is helpful in the astrometry of ISS images in a fully automatic manner.

关键词： methods:data analysis techniques:image processing techniques:telescopes stars:imaging

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Early-fusion based pulsar identification with smart under-sampling

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Research in Astronomy and Astrophysics 2021年第10期21卷 164-174页

作者： Shi-Chuan Zhang Xiang-Cong Kong Yue-Ying Zhou Ling-Yao Chen Xiao-Ying Zheng Chun-Ling Xu Bao-Qiang Lao Tao An Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China j Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China

The discovery of pulsars is of great significance in the field of physics and *** the astronomical equipment produces a large number of pulsar data,an algorithm for automatically identifying pulsars becomes *** propose a deep learning framework for pulsar *** response to the extreme imbalance between positive and negative examples and the hard negative sample issue presented in the High Time Resolution Universe Medlat Training Data,there are two coping strategies in our framework:the smart under-sampling and the improved loss *** also apply the early-fusion strategy to integrate features obtained from different attributes before classification to improve the *** our best knowledge,this is the first study that integrates these strategies and techniques in pulsar *** experiment results show that our framework outperforms previous works with respect to either the training time or F 1 *** can not only speed up the training time by 10×compared with the state-ofthe-art work,but also get a competitive result in terms of F1 score.

关键词： methods:data analysis (stars:)pulsars:general techniques:image processing

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Adaptive scale model reconstruction for radio synthesis imaging

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Research in Astronomy and Astrophysics 2021年第3期21卷 117-127页

作者： Li Zhang Li-Gong Mi Long Xu Ming Zhang Dan-Yang Li Xiang Liu Feng Wang Yi-Fan Xiao Zhong-Zu Wu College of Big Data and Information Engineering Guizhou UniversityGuiyang 550025China Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China Key Laboratory of Radio Astronomy Chinese Academy of SciencesUrumqi 830011China Center for Astrophysics Guangzhou UniversityGuangzhou 510006China College of Physics Guizhou UniversityGuiyang 550025China

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 *** 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 *** 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 *** Very Large Array(JVLA),an SKA *** show that the new algorithm can reconstruct more physical models with rich *** work is a step forward for future SKA image reconstruction and developing SKA imaging pipelines.

关键词： methods:data analysis techniques:image processing techniques:interferometric

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Automated classification technique for edge-on galaxies based on mathematical treatment of brightness data

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Research in Astronomy and Astrophysics 2021年第10期21卷 231-238页

作者： Mohamed Eassa Ibrahim Mohamed Selim Walid Dabour Passent Elkafrawy Computer Science Department Integrated Thebes InstituteCairoEgypt Faculty of Computer&Artificial Intelligence Sadat City UniversitySadat CityEgypt Math and Computer Science Dept. Faculty of ScienceMenoufia UniversityEgypt Computer Science Dept. Taibah UniversityAlula BranchKingdom of Saudi Arabia School of Information Technology and Computer Science(ITCS) Nile UniversityEgypt

Classification of edge-on galaxies is important to astronomical studies due to our Milky Way galaxy being an edge-on ***-on galaxies pose a problem to classification due to their less overall brightness levels and smaller numbers of *** the current work,a novel technique for the classification of edge-on galaxies has been *** technique is based on the mathematical treatment of galaxy brightness data from their images.A special treatment for galaxies’brightness data is developed to enhance faint galaxies and eliminate adverse effects of high brightness backgrounds as well as adverse effects of background bright stars.A novel slimness weighting factor is developed to classify edge-on galaxies based on their *** technique has the capacity to be optimized for different catalogs with different brightness *** the current work,the developed technique is optimized for the EFIGI catalog and is trained using a set of 1800 galaxies from this *** classification of the full set of 4458 galaxies from the EFIGI catalog,an accuracy of 97.5% has been achieved,with an average processing time of about 0.26 seconds per galaxy on an average laptop.

关键词： techniques:image processing methods:data analysis galaxies:formation

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High-resolution Solar image Reconstruction Based on Non-rigid Alignment

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Research in Astronomy and Astrophysics 2022年第9期22卷 63-71页

作者： Hui Liu Zhenyu Jin Yongyuan Xiang Kaifan Ji Yunnan Observatories Chinese Academy of SciencesKunming 650216China

Suppressing the interference of atmospheric turbulence and obtaining observation data with a high spatial resolution are an issue to be solved urgently for ground observations. One way to solve this problem is to perform a statistical reconstruction of short-exposure speckle images. Combining the rapidity of Shift-Add and the accuracy of speckle masking, this paper proposes a novel reconstruction algorithm-NASIR(Non-rigid Alignment based Solar image Reconstruction). NASIR reconstructs the phase of the object image at each frequency by building a computational model between geometric distortion and intensity distribution and reconstructs the modulus of the object image on the aligned speckle images by speckle interferometry. We analyzed the performance of NASIR by using the correlation coefficient, power spectrum, and coefficient of variation of intensity profile in processing data obtained by the NVST(1 m New Vacuum Solar Telescope). The reconstruction experiments and analysis results show that the quality of images reconstructed by NASIR is close to speckle masking when the seeing is good, while NASIR has excellent robustness when the seeing condition becomes worse. Furthermore, NASIR reconstructs the entire field of view in parallel in one go, without phase recursion and block-by-block reconstruction, so its computation time is less than half that of speckle masking. Therefore, we consider NASIR is a robust and highquality fast reconstruction method that can serve as an effective tool for data filtering and quick look.

关键词： methods:data analysis techniques:image processing Sun:chromosphere Sun:photosphere instrumentation:high angular resolution

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