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Orbit determination Using Satellite-to-Satellite Tracking Data

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Chinese Journal of astronomy and Astrophysics 2001年第3期1卷 281-286页

作者： ying－Chunliu Linliu departmentofastronomy NanjingUniversityNanjing210093 departmentofastronomy NanjingUniversityNanjing

Satellite-to-Satellite tricking (SST) data can be used to determine the orbits of spacecraft in two ways. One is combined orbit determination, which combines SST data with ground-based tracking data and exploits the enhanced tracking geometry. The other is the autonomous orbit determination, which uses only SST. The latter only fits some particular circumstances since it suffers the rank defect problem in other circumstances. The proof of this statement is presented. The nature of the problem is also investigated in order to find an effective solution. Several. methods of solution are discussed. The feasibility of the methods is demonstrated by their application to a simulation.

关键词： Celestial mechanics: orbit determination - Methods: miscellaneous

Observation of topological charge transformations in acoustic vortex using passive periodic systems

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Science China(Physics,Mechanics & astronomy) 2025年第1期Mechanics & Astronomy) .卷 140-147页

作者： Di-Chao Chen Xie liu Changqing Xu Da-Jian Wu ying Cheng Xiao-Jun liu School of Physics and Technology Nanjing Normal University Key Laboratory of Modern Acoustics School of Physics Nanjing University

Vortex transmutation utilizes a periodic system, which not only enables the alteration of the topological charge(TC) of unstable input vortices but also facilitates their transformation into stable structures. This approach is crucial for investigating the characteristics of vortices in various wave systems. Here, we achieve acoustic vortex TC transmutation by employing a welldesigned dual-structured plate external system(DPES). The interactions between the acoustic vortex and the finite-order discrete rotational symmetry lead to the transformation of its topological charge when complete rotational symmetry is broken to Nthorder discrete symmetry. Our results experimentally demonstrate the acoustic vortex TC transmutation based on passive artificial structures, enabling numerous applications in particle manipulation and information multiplexing as well as advancing our understanding and control over free-space acoustic vortices.

关键词： acoustic vortex topological charge transformation artificial structure

Analysis of the Distribution,Rotation and Scale Characteristics of Solar Wind Switchbacks:Comparison between the First and Second Encounters of Parker Solar Probe

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Research in astronomy and Astrophysics 2022年第3期22卷 178-185页

作者： ming-ming Meng ying D.liu Chong Chen Rui Wang State Key Laboratory of Space Weather National Space Science CenterChinese Academy of SciencesBeijing 100190China university of Chinese Academy of Sciences Beijing 100049China

The S-shaped magnetic structure in the solar wind formed by the twisting of magnetic field lines is called a switchback,whose main characteristics are the reversal of the magnetic field and the significant increase in the solar wind radial *** identify 242 switchbacks during the first two encounters of Parker Solar *** methods are applied to analyze the distribution and the rotation angle and direction of the magnetic field rotation of the *** diameter of switchbacks is estimated with a minimum variance analysis(MVA)method based on the assumption of a cylindrical magnetic *** also make a comparison between switchbacks from inside and the boundary of coronal *** main conclusions are as follows:(1)the rotation angles of switchbacks observed during the first encounter seem larger than those of the switchbacks observed during the second encounter in general;(2)the tangential component of the velocity inside the switchbacks tends to be more positive(westward)than in the ambient solar wind;(3)switchbacks are more likely to rotate clockwise than counterclockwise,and the number of switchbacks with clockwise rotation is 1.48 and 2.65 times those with counterclockwise rotation during the first and second encounters,respectively;(4)the diameter of switchbacks is about 10;km on average and across five orders of magnitude(10^(3)–10^(7)km).

关键词： ISM:magnetic fields methods:statistical (Sun:)solar wind

A Wideband Microwave Holography Methodology for Reflector Surface Measurement of Large Radio Telescopes

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Research in astronomy and Astrophysics 2022年第9期22卷 140-151页

作者： Zan Wang de-Qing Kong Hong-Bo Zhang Xin-ying Zhu Ze-Xin liu Yu-Chen liu Key Laboratory of Lunar and deep Space Exploration National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100010China university of Chinese Academy of Sciences Beijing 100049China

Most reflector surface holographic measurements of a large radio telescope utilize a geostationary satellite as the signal source. The shortcoming is that those measurements could only be done at a limited elevation angle due to the satellite’s relatively stationary state. This paper proposed a new wideband microwave holographic measurement method based on radio sources to achieve full-elevation-angle measurement with small size reference antenna. In theoretical derivation, the time delay and phase change due to path length and device difference between the antenna under test and reference antenna are compensated first. Then the correct method of wideband holography effect, which is because of antenna pattern differing under different wavelengths when receiving a wideband signal, is presented. To verify the proposed methodology, a wideband microwave holographic measurement system is established, the data processing procedure is illustrated, and the reflector surface measurement experiments on a 40 m radio telescope at different elevation angles are conducted. The result shows that the primary reflector surface root-mean-square at around elevation angles of 28°, 44°, 49°, and 75° are respectively 0.213 mm, 0.170 mm, 0.188 mm, and 0.199 mm. It is basically consistent with the real data, indicating that the proposed wideband microwave holography methodology is feasible.

关键词： astronomical instrumentation methods and techniques telescopes methods:analytical atmospheric effects

Obtaining space-based SDO/AIA solar UV and EUV images from ground-based Hαobservations by deep learning

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Research in astronomy and Astrophysics 2021年第6期21卷 233-240页

作者： Tie liu ying-Na Su Li-ming Xu Hai-Sheng Ji Key Laboratory of Dark Matter and Space astronomy Purple Mountain ObservatoryChinese Academy of SciencesNanjing 210023China School of astronomy and Space Science University of Science and Technology of ChinaHefei 230026China Jiangsu Urban and Rural Construction College Changzhou 213147China

In this work,we explore the mappings from solar images taken in Hα(6563 A)by the Global Oscillation Network Group(GONG)on the ground to those observed in eight different wavelengths(94,131,171,193,211,304,335 and 1600 A)by SDO/AIA in *** mappings are built by training the conditional Generative Adversarial Networks(cGANs)on datasets with 500 paired images,which are[Hα,AIA94],[Hα,AIA131],[Hα,AIA171],[Hα,AIA193],[Hα,AIA211],[Hα,AIA304],[Hα,AIA335]and[Hα,AIA1600].We evaluate the eight trained cGANs models on validation and test datasets with 154-pair images and 327-pair images,*** model generated fake AIA images match the corresponding observed AIA images well on large-scale structures such as large active regions and *** the small-scale flare loops and filament threads are difficult to *** quantitative comparisons are carried out on the validation and test datasets to score the *** find that the model-generated images in 304 and 1600 A match the corresponding observed images *** exploration suggests that the cGANs are promising methods for mappings between ground-based Ha and space-based EUV/UV images,while some improvements are necessary.

关键词： methods:analytical techniques:image processing Sun:corona Sun:UV radiation

Investigating the disk-corona relation in a blue AGN sample

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Research in astronomy and Astrophysics 2009年第9期9卷 966-978页

作者： Jie-ying liu Bi-Fang liu National Astronomical Observatories / Yunnan Observatory Chinese Academy of SciencesKunming 650011 China Graduate university of Chinese Academy of Sciences Beijing 100049 China

We compile a blue AGN sample from SDSS and investigate how the ratio of hard X-ray to bolometric luminosity depends on the Eddington ratio and black hole mass. Our sample comprises 240 radio-quiet Seyfert 1 galaxies and QSOs. We find that the fraction of hard X-ray luminosity （log（L2-10keV/L bol）） decreases with an increase of the Eddington ratio. We also find that the fraction of hard X-ray luminosity is independent of the black hole mass for radio-quiet AGNs. The relation of log（L2-10 keV/Lbol） decreasing with increasing Eddington ratio indicates that X-ray bolometric correction is not a constant, from a larger sample supporting the results of Vasudevan ＆ Fabian. We interpret our results by the disk corona evaporation/condensation model. In the frame work of this model, Compton cooling becomes efficient in cooling the corona at high accretion rates （in units of Eddington rate）, leading to condensation of coronal gas to the disk. Consequently, the relative strength of the corona to the disk becomes weaker at higher Eddington ratios. Therefore, the fraction of hard X-ray emission to disk emission and hence to the bolometric emission is smaller at higher Eddington ratios. The independence of the fraction of hard X-ray luminosity with respect to the mass of the black hole can also be explained by the disk corona model since the coronal structure and luminosity （in units of Eddington luminosity） are independent of the mass of black holes.

关键词： accretion: accretion disks -- galaxies: active -- X-rays: galaxies

A New Method of Frequency Fluctuation Estimation and IPS Processing Results Based on the Downlink Signal of Tianwen-1

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Research in astronomy and Astrophysics 2023年第8期23卷 332-345页

作者： Yu-Chen liu de-Qing Kong Dong-Hao liu Xin-ying Zhu Yan Su Hong-Bo Zhang Zan Wang Key Laboratory of Lunar and deep Space Exploration National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China university of Chinese Academy of Sciences Beijing 100049China

The radio-occultation observations taken by Tianwen-1 are aiming to study the properties of solar wind.A new method of frequency fluctuation(FF)estimation is presented for processing the down-link signals of Tianwen-1 during the occultation period to study the properties of the coronal plasma at the heliocentric distances of 4.48–19 R_(⊙).Because of low S/N as well as the phase fluctuation phenomena caused by solar activity,a Kalman based on polynomial prediction methods is proposed to avoid the phase locked loop loss lock.A new detrend method based on multi-level iteration correction is proposed to estimate Doppler shift to get more accurate power density spectra of FF in the low frequency *** data analyze procedure is used to get the properties of the solar corona during the *** method was finally verified at the point when the solar offset is 5.7 R_(⊙),frequency tracking was successfully performed on data with a carrier-to-noise ratio of about 28 *** density spectra obtained by the improved method are basically the same when the frequency is greater than 2 mHz,the uncertainty in the result of the rms of the FF obtained by removing the trend term with different order polynomials is less than 3.3%.The data without eliminating interference show a large error for different detrending orders,which justifies the need for an improved ***,the frequency fluctuation results combined with the information on intensity fluctuation obtained by the new method are compared with the results of the integrated Space Weather Analysis system and theoretical formula,which verifies that the processing results in this paper have a certain degree of credibility.

关键词： methods data analysis Sun corona-Sun heliosphere-(Sun:)solar wind-Physical Data and Processes

R-band host galaxy contamination of TeV γ-ray blazar Mrk 501： effects of aperture size and seeing

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Research in astronomy and Astrophysics 2018年第2期18卷 93-104页

作者： Hai-Cheng Feng Hong-Tao liu ying-He Zhao Jin-ming Bai Fang Wang Xu-Liang Fan Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China university of Chinese Academy of Sciences Beijing 100049 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China Center for Astronomical Mega-Science Chinese Academy of Sciences Beijing 100012 China School of Physics and Space Science China West Normal University Nanchong 637009 China School of Physics Huazhong University of Science and Technology Wuhan 430074 China

We simulated the R-band contribution of the host galaxy of TeV γ-ray BL Lac object Mrk 501 in different aperture sizes and seeing conditions. An intensive set of observations was acquired with the 1.02m optical telescope, managed by Yunnan Observatories, from 2010 May 15 to 18. Based on the host subtraction data usually used in the literature, the subtraction of host galaxy contamination results in significant seeing-brightness correlations. These correlations would lead to illusive large amplitude variations at short timescales, which will mask the intrinsic microvariability, thus giving rise to difficulty in detecting the intrinsic microvariability. Both aperture size and seeing condition influence the flux measurements, but the aperture size impacts the result more significantly. Based on the parameters of an elliptical galaxy provided in the literature, we simulated the host contributions of Mrk 501 in different aperture sizes and seeing conditions. Our simulation data of the host galaxy obviously weaken these significant seeing-brightness correlations for the host-subtracted brightness of Mrk 501, and can help us discover the intrinsic short timescale microvariability. The pure nuclear flux is -8.0 mJy in the R band, i.e., the AGN has a magnitude of R - 13.96 mag.

关键词： galaxies: active - BL Lacertae objects: individual (Mrk 501) - techniques: photometric-- methods: data analysis

Charm physics with overlap fermions on 2+1-flavor domain wall fermion configurations

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Chinese Physics C 2024年第12期48卷 50-62页

作者： Dong-Hao Li ying Chen ming Gong Keh-Fei liu Zhaofeng liu Ting-Xiao Wang MOE Frontiers Science Center for Rare Isotopes and School of Nuclear Science and TechnologyLanzhou UniversityLanzhou 730000China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China department of Physics and astronomy University of KentuckyLexingtonKentucky 40506USA Nuclear Science Division Lawrence Berkeley National LaboratoryBerkeleyCalifornia 94720USA Center for High Energy Physics Peking UniversityBeijing 100871China

decay constants of pseudoscalar mesons D,D_(s),η_(c) and vector mesons D^(*),D_(s)^(*),J/ψ are determined from the N_(f)=2+1 lattice QCD at a lattice spacing a~0.08 *** vector mesons,the decay constants defined by tensor currents are given in the MS scheme at 2 *** calculation is performed on domain wall fermion configurations generated by the RBC-UKQCD collaborations and the overlap fermion action is used for the valence *** the current results with our previous results at a coarser lattice spacing a ~0.11 fm provides a better understanding of the discretization *** obtain f_(D_(s)^(*))^(T)(MS,2 GeV)/f_(D_(s)^(*))=0.909(18)with a better precision than our previous *** our f_(D_(s)^(*))=277(11)MeV with the total width of D_(s)^(*) determined in a recent study gives a branching fraction 4.26(52)×10^(-5) for D_(s)^(*) leptonic decay.

关键词： charmed meson decay constants lattice QCD leptonic decays charmonium decay constants vector meson decay constants overlap fermions