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Pose optimization of the FAST feed support system based on the new feed cabin mechanism

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Science China(Physics,Mechanics & Astronomy) 2023年第3期66卷 178-187页

作者： Jianing Yin Peng Jiang Rui Yao CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST) is the largest and most sensitive single-dish radio telescope in the world and has made many important scientific achievements in a few years. Given the enormous scientific research potential of the Milky Way center, it is necessary to enhance the observation zenith angle as close to the Milky Way center as possible. In this regard, a new mechanism for the feed cabin is proposed with cables and sliders, which is lighter in weight and larger in the workspace. This paper will introduce this new feed cabin and the whole feed support system and establish their mechanical models to optimize the relevant control parameters, making FAST achieve an observation zenith angle of at least 50°with satisfying the required constraints. It indicates that the new mechanism designed by the FAST team can be used for the FAST upgrade and the future FAST array project.

关键词： radio telescope cable-driven parallel robot mechanism optimization

Cross-correlation of 21 cm and soft X-ray backgrounds during the epoch of reionization

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Research in Astronomy and Astrophysics 2016年第8期16卷 135-144页

作者： Jun-Min Liang Xiao-Chun Mao Bo Qin National Astronomical Observatories Chinese Academy of Sciences

The cross-correlation between the high-redshift 21 cm background and the Soft X-ray Background （SXB） of the Universe may provide an additional probe of the Epoch of Reionization. Here we use semi-numerical simulations to create 21 cm and soft X-ray intensity maps and construct their cross power spectra. Our results indicate that the cross power spectra are sensitive to the thermal and ionizing states of the intergalactic medium （IGM）. The 21 cm background correlates positively to the SXB on large scales during the early stages of the reionization. However as the reionization develops, these two back- grounds turn out to be anti-correlated with each other when more than - 15% of the IGM is ionized in a warm reionization scenario. The anti-correlated power reaches its maximum when the neutral fraction declines to 0.2-0.5. Hence, the trough in the cross power spectrum might be a useful tool for tracing the growth of HII regions during the middle and late stages of the reionization. We estimate the detectability of the cross power spectrum based on the abilities of the Square Kilometre Array and the Wide Field X-ray Telescope （WFXT）, and find that to detect the cross power spectrum, the pixel noise of X-ray images has to be at least 4 orders of magnitude lower than that of the WFXT deep survey.

关键词： cosmic background radiation -- cosmology： theory -- dark ages reionization first stars --early Universe -- diffuse radiation -- X-rays： diffuse background

Non-ballistic motion and precessing helical trajectory in quasar NRAO 150

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Research in Astronomy and Astrophysics 2016年第1期16卷 175-189页

作者： Shan-Jie Qian National Astronomical Observatories Chinese Academy of Sciences

NRAO 150 is a very special radio quasar in which prominent non-ballistic superluminal motion has been observed in its inner-jet region. We apply model-fittings to the kinematics of the superluminal knots（trajectory, distance from the core and apparent velocity） in terms of a helical precessing jet-nozzle model.Five cases are considered in which the angle between the jet axis and the line of sight is assumed to be 6？,3？, 1？, 0.6？ and 0.12？, respectively. It is shown that the superluminal components have intrinsic acceleration in the innermost regions（≤0.2 mas from the core）. The phenomenon of precessing nozzle/trajectory can be understood on the basis of relativistic magnetohydrodynamic theories for relativistic jets.

关键词： radio continuum： galaxies -- galaxies： jets -- galaxies： kinematics -- galaxies： individual（quasar NRAO 150）

Reminiscence of my Sixty-five year Voyage in Astronomy

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Research in Astronomy and Astrophysics 2016年第6期16卷 1-12页

作者： Shouguan Wang National Astronomical Observatories Chinese Academy of Sciences

I returned to China from the United Kingdom in 1953, then worked in Purple Mountain Observatory. It was the early days of new China. The elder generation of astronomers was undertaking an effort of ＂repairing broken and filling defect＂ during those post-war years, and started planning and lay- ing the foundation of modern astronomy. Under their leadership, I started a journey of astronomy whose main task was construction. The journey has been full of twists and turns. As a result of the ＂Great Leap Forward＂ in 1958 and the 1966 launch of the decade-long ＂Cultural Revolution＂ period, the situation of construction in astronomy was similar to that in other sciences, suffering bad effects. Not until the ＂Reform and Opening up＂ period after those events was construction able to continue, and various disciplines and international connections began to open. A ＂passage＂ had gradually developed. In this new circumstance, I kept pursuing the pioneers to explore a forward direction. Looking back today, this journey has been three periods of a four generation relay. This article is divided into three sections that describe my research work in these times that I recall：（1） Looking back at the beginning of the return and tracing the footprints of the founders. （2） Recalling my radio astronomy tour. （3） Retrospection and expectation of LAMOST.

关键词： LAMOST Reminiscence of my Sixty-five year Voyage in Astronomy

Terrain reconstruction from Chang'e-3 PCAM images

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Research in Astronomy and Astrophysics 2015年第7期15卷 1057-1067页

作者： Wen-Rui Wang Xin Ren Fen-Fei Wang Jian-Jun Liu Chun-Lai Li National Astronomical Observatories Chinese Academy of Sciences

The existing terrain models that describe the local lunar surface have limited resolution and accuracy, which can hardly meet the needs of rover navigation,positioning and geological analysis. China launched the lunar probe Chang＇e-3 in December, 2013. Chang＇e-3 encompassed a lander and a lunar rover called ＂Yutu＂（Jade Rabbit）. A set of panoramic cameras were installed on the rover mast. After acquiring panoramic images of four sites that were explored, the terrain models of the local lunar surface with resolution of 0.02 m were reconstructed. Compared with other data sources, the models derived from Chang＇e-3 data were clear and accurate enough that they could be used to plan the route of Yutu.

关键词： space vehicles： rover -- space vehicles： instruments： panoramic camera-- methods： terrain reconstruction -- techniques： image processing： orthoimage

Prognostics and health management of FAST cable-net structure based on digital twin technology

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Research in Astronomy and Astrophysics 2020年第5期20卷 109-116页

作者：李庆伟姜鹏李辉 National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China CAS Key Laboratory of FAST National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)will be fully commissioned later in 2019.Once commissioned,operation and maintenance of FAST will be the most prominent task.The unique working mode of active shape-changing of FAST cable-net structure makes the traditional maintenance way,which combines routine inspection with preventive maintenances not only expensive,but also unable to effectively avoid potential risks in operations.Therefore,it is necessary to develop an economical and reliable operation/maintenance technology for FAST cable-net structure.In this paper,a Prognostics and Health Management(PHM)system is proposed based on the advanced Digital Twin(DT)technology.Through the finite element analysis of DT model,the current safety status of FAST cablenet is evaluated,and the fatigue life of components in the cable-net is predicted.Hence Condition-Based Maintenance(CBM)of FAST cable-net structure can be realized.The PHM system described in this paper can effectively guarantee the healthy and safe operation of the FAST cable-net structure,greatly improve the maintenance efficiency and reduce the cost for maintenance works.

关键词： telescopes astronomical instrumentation methods and techniques methods:analytical methods:data analysis

The first data release of LAMOST low-resolution single-epoch spectra

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Research in Astronomy and Astrophysics 2021年第10期21卷 73-85页

作者：白仲瑞张昊彤袁海龙樊东卫何勃亮雷亚娟董义乔余思成赵永恒张勇侯永辉禇耀泉 CAS Key Laboratory of Optical Astronomy National Astronomical ObservatoriesBeijing 100101China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China national astronomical Data Center Beijing 100101China Nanjing Institute of astronomical Optics&Technology National Astronomical ObservatoriesChinese Academy of SciencesNanjing 210042China University of Science and Technology of China Hefei 230026China

LAMOST Data Release 5,covering 17000 deg^(2) from-10°to 80°in declination,contains 9 million co-added low-resolution spectra of celestial objects,each spectrum combined from repeat exposure of two to tens of times during Oct 2011 to Jun 2017.In this paper,we present the spectra of individual exposures for all the objects in LAMOST Data Release 5.For each spectrum,the equivalent width of 60lines from 11 different elements are calculated with a new method combining the actual line core and fitted line wings.For stars earlier than F type,the Balmer lines are fitted with both emission and absorption profiles once two components are detected.Radial velocity of each individual exposure is measured by minimizing χ^(2) between the spectrum and its best template.The database for equivalent widths of spectral lines and radial velocities of individual spectra are available online.Radial velocity uncertainties with different stellar type and signal-to-noise ratio are quantified by comparing different exposure of the same objects.We notice that the radial velocity uncertainty depends on the time lag between observations.For stars observed in the same day and with signal-to-noise ratio higher than 20,the radial velocity uncertainty is below 5 km s^(-1),and increases to 10 km s^(-1) for stars observed in different nights.

关键词： surveys stars:general methods:data analysis

Model simulation for periodic double-peaked outbursts in blazar OJ 287: binary black hole plus lighthouse effect

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Research in Astronomy and Astrophysics 2015年第5期15卷 687-712页

作者： Shan-Jie Qian National Astronomical Observatories Chinese Academy of Sciences

The mechanism of formation for double-peaked optical outbursts observed in blazar OJ 287 is studied. It is shown that they could be explained in terms of a light- house effect for superluminal optical knots ejected from the center of the galaxy that move along helical magnetic fields. It is assumed that the orbital motion of the secondary black hole in the supermassive binary black hole system induces the 12-year quasi-periodicity in major optical outbursts by the interaction with the disk around the primary black hole. This interaction between the secondary black hole and the disk of the primary black hole （e.g. tidal effects or magnetic coupling） excites or injects plas- mons （or relativistic plasmas plus magnetic field） into the jet which form superluminal knots. These knots are assumed to move along helical magnetic field lines to produce the optical double-peaked outbursts by the lighthouse effect. The four double-peaked outbursts observed in 1972, 1983, 1995 and 2005 are simulated using this model. It is shown that such lighthouse models are quite plausible and feasible for fitting the double-flaring behavior of the outbursts. The main requirement may be that in OJ 287 there exists a rather long （～40-60 pc） highly collimated zone, where the lighthouse effect occurs.

关键词： optical continuum -- galaxies jets -- galaxies kinematics -- galaxies variability -- galaxies individual （blazar OJ 287）

Structure function analysis of RISS and model-fitting to J1128+5925

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Research in Astronomy and Astrophysics 2015年第1期15卷 37-44页

作者： Bin Liu Bo Peng Li-Jia Liu National Astronomical Observatories Chinese Academy of Sciences

There has been great progress recently in the study of radio variability, including the phenomenon of intraday variability（IDV） which occurs on short timescales of 50 h or less. There are two common explanations for IDV： an intrinsic mechanism or the effect of radio propagation through the interstellar medium. We consider the case of refractive interstellar scintillation（RISS）, an extrinsic cause of radio variability. We theoretically derive the structure function of the ‘thick screen’RISS model by using an approximation method, and discuss its application to the IDV phenomenon with some simulated results. Finally, the IDV source J1128＋5925 is fitted with the ‘thin screen’ RISS model. Some possible combinations of parameters, namely source size, distance and relative velocity of the scattering screen, are presented.

关键词： radio variable source refractive scintillation structure function,IDV