Astronomical site selection work is very hard.Unmanned technologies are important trends and solutions.We present a relatively easy method to plan a high reliability site selection which can extend the time from site ...Astronomical site selection work is very hard.Unmanned technologies are important trends and solutions.We present a relatively easy method to plan a high reliability site selection which can extend the time from site deployment to returning for maintaining by unmanned confirming the site.First,we redefine the reliability of a site selection deployment with the parameter of the trusty time,which means when we must return,and which can be relatively easy for estimating.The redefinition makes the reliability parameter as a Bayesian probability,and can be obtained by estimating besides testing,which makes the evaluation of each device's reliability much easier.Then we use block diagram tools in the Matlab Simulink software to construct structure diagram,and to link each component with relations of parallel,serial,protection,and so on.This makes the whole reliability value can be calculated at the time when we design or plan a site selection.We applied this concept and method in an actual site selection in Lenghu,Qinghai Province,China.The survey practice reveals its effectiveness and simpleness.展开更多
The proposed design of a microwave superconducting kinetic inductance detector(MKID)array readout system characterizes the performance of MKIDs through a digital homodyne frequency mixing architecture.Meanwhile,the re...The proposed design of a microwave superconducting kinetic inductance detector(MKID)array readout system characterizes the performance of MKIDs through a digital homodyne frequency mixing architecture.Meanwhile,the readout system is implemented using a frequency division multiplexing circuit system,coupled with an FFT design to enable the readout of MKID arrays.The system is characterized by its compact size,low cost,portability,and ease of further development.Together,these features have significant implications for the design and readout of terahertz MKID arrays,while simultaneously advancing both the theoretical and practical aspects of MKID technology.展开更多
The Wide Field Survey Telescope(WFST)is located at 4200 m on Saishiteng Mountain in Lenghu,Qinghai Province,China.It features a primary mirror with a diameter of 2.5 m and a camera equipped with nine CCDs,providing a ...The Wide Field Survey Telescope(WFST)is located at 4200 m on Saishiteng Mountain in Lenghu,Qinghai Province,China.It features a primary mirror with a diameter of 2.5 m and a camera equipped with nine CCDs,providing a wide field of view of approximately 3×3 square degrees.Calibration parameters are essential to ensure the precision of astrometric observations with the WFST.These parameters are derived from geometric distortion(GD)and gaps through astrometric modeling and are subsequently validated via the Yao’An High Precision Telescope(YAHPT).The GD solutions show maximum distortions between 1.18 and 10.29 pixels for the WFST chips,with central chips exhibiting lower distortion.After applying the GD correction,the precision of the WFST reaches 4 mas.The interchip gaps of the WFST range from 1.922 mm to 7.765 mm,corresponding to 10μm/pixel,aligning with the design and measurements.The calibrated parameters guarantee that the WFST can perform highly accurate astrometric measurements.Furthermore,as the WFST undergoes updates,the parameter model remains consistently applicable.展开更多
This paper presents a comprehensive analysis of the photometric system of the University of Chinese Academy of Sciences 70 cm Telescope located at the Yan-qi Lake campus of the University of Chinese Academy of Science...This paper presents a comprehensive analysis of the photometric system of the University of Chinese Academy of Sciences 70 cm Telescope located at the Yan-qi Lake campus of the University of Chinese Academy of Sciences.We evaluated the linearity,bias stability,and dark current of the camera.Utilizing the Johnson-Cousins Blue-Visible-Red-Infrared filter system and an Andor DZ936 charge-coupled device camera,we conducted extensive observations of Landolt standard stars to determine the color terms,atmospheric extinction coefficients,photometric zero-points,and the sky background brightness.The results indicate that this telescope demonstrates excellent performance in photometric calibration and good system performance overall,meeting the requirements for limited scientific research and teaching purposes.展开更多
We perform a time-resolved statistical study of GRB 221009A’s X-ray emission using Swift XRT Photon Counting and Windowed Timing data.After standard reduction(barycentric correction,pile-up,background subtraction via...We perform a time-resolved statistical study of GRB 221009A’s X-ray emission using Swift XRT Photon Counting and Windowed Timing data.After standard reduction(barycentric correction,pile-up,background subtraction via HEASOFT),we extracted light curves for each observational ID and for their aggregation.Countrate histograms were fitted using various statistical distributions;fit quality was assessed by chi-squared and the Bayesian Information Criterion.The first observational segment is best described by a Gaussian distribution(χ^(2)=68.4;BIC=7651.2),and the second by a Poisson distribution(χ^(2)=33.5;BIC=4413.3).When all segments are combined,the lognormal model provides the superior fit(χ^(2)=541.9;BIC=34365.5),indicating that the full data set’s count rates exhibit the skewness expected from a multiplicative process.These findings demonstrate that while individual time intervals conform to discrete or symmetric statistics,the collective emission profile across multiple observations is better captured by a lognormal distribution,consistent with complex,compounded variability in GRB afterglows.展开更多
The SiTian Project represents a groundbreaking initiative in astronomy,aiming to deploy a global network of telescopes,each with a 1 m aperture,for comprehensive time-domain sky surveys.The network's innovative ar...The SiTian Project represents a groundbreaking initiative in astronomy,aiming to deploy a global network of telescopes,each with a 1 m aperture,for comprehensive time-domain sky surveys.The network's innovative architecture features multiple observational nodes,each comprising three strategically aligned telescopes equipped with filters.This design enables three-color(g,r,i)channel imaging within each node,facilitating precise and coordinated observations.As a pathfinder to the full-scale project,the Mini-SiTian Project serves as the scientific and technological validation platform,utilizing three 30 cm aperture telescopes to validate the methodologies and technologies planned for the broader SiTian network.This paper focuses on the development and implementation of the Master Control System(MCS),and the central command hub for the Mini-SiTian Array.The MCS is designed to facilitate seamless communication with the SiTian Brain,the project's central processing and decisionmaking unit,while ensuring accurate task allocation,real-time status monitoring,and optimized observational workflows.The system adopts a robust architecture that separates front-end and back-end functionalities.A key innovation of the MCS is its ability to dynamically adjust observation plans in response to transient source alerts,enabling rapid and coordinated scans of target sky regions.The paper provides an in-depth analysis of the system's internal components,including the communication system,which is critical for seamless network operation.Extensive testing has validated the functionality,reliability,and compatibility of these components within the overall system architecture.The successful deployment of the MCS in managing the Mini-SiTian Array has demonstrated its practicality and efficacy in collaborative observation and distributed control.By simplifying cluster management and ensuring data integrity,the MCS represents a significant advancement in astronomical observation control systems.Its scalable and adaptable design not only supports the future expansion of the SiTian network but also provides a blueprint for other large-scale telescope arrays,marking a transformative step forward in time-domain astronomy.展开更多
Dome A,Antarctica,has been thought to be one of the best astronomical sites on the Earth for decades.Since it was first visited by astronomers in 2008,dozens of facilities for astronomical observation and site testing...Dome A,Antarctica,has been thought to be one of the best astronomical sites on the Earth for decades.Since it was first visited by astronomers in 2008,dozens of facilities for astronomical observation and site testing were deployed.Due to its special geographical location,the data and message exchange between Dome A and the domestic control center could only depend on Iridium.Because the link bandwidth of Iridium is extremely limited,the network traffic cost is quite expensive and the network is rather unstable,the commonly used data transfer tools,such as rsync and scp,are not suitable in this case.In this paper,we design and implement a data transfer tool called NBFTP(narrow bandwidth file transfer protocol)for the astronomical observation of Dome A.NBFTP uses a uniform interface to arrange all types of data and matches specific transmission schemes for different data types according to rules.Break-point resuming and extensibility functions are also implemented.Our experimental results show that NBFTP consumes 60%less network traffic than rsync when detecting the data pending to be transferred.When transferring small files of 1 KB,the network traffic consumption of NBFTP is 40%less than rsync.However,as the file size increases,the network traffic consumption of NBFTP tends to approach rsync,but it is still smaller than rsync.展开更多
The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a di...The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.展开更多
In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous wor...In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous work,our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale,with a more pronounced influence as the size of the focal plane increases.Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions.The apparent scale variation follows a sinusoidal distribution throughout one orbital period.Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude.At low ecliptic latitudes,the total aberration leads to about a 0.94 pixel offset(a 20 minute exposure)and a 0.26 pixel offset(a 300 s exposure)at the edge of the field of view.Appropriate processings for the geometric effect during the CSST pre-and post-observation phases are presented.展开更多
We introduce the structure of a radio astronomy phased array feeds(PAF)beamforming demonstrator.In a laboratory environment,we have demonstrated beamforming on a received 1.25 GHz sinusoidal signal and used digital we...We introduce the structure of a radio astronomy phased array feeds(PAF)beamforming demonstrator.In a laboratory environment,we have demonstrated beamforming on a received 1.25 GHz sinusoidal signal and used digital weighting techniques to plot the 2D pattern of the PAF.The radio frequency part of the demonstrator includes a 4×4 linearly polarized microstrip antenna array,all of which is connected in series with a low-noise amplifier.The signals from the central 4×2 array elements are injected into a radio frequency system-on-chip digital board,which can receive eight inputs with a bandwidth of 512 MHz.Combining the principle of undersampling,the beamforming is completed at a frequency of 1.25 GHz for the offline data,and a 2D image of the beam is plotted using beam scanning technology.展开更多
The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of...The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.展开更多
With the growing significance of space weather forecasting,multi-layer magnetic and helioseismic telescopes are emerging as a key area of research.However,owing to the diverse operational processes and sophisticated h...With the growing significance of space weather forecasting,multi-layer magnetic and helioseismic telescopes are emerging as a key area of research.However,owing to the diverse operational processes and sophisticated hardware configurations of these devices,there is an urgent need for efficient autonomous observation capabilities.An autonomous Master Control System(MCS)can ensure efficient performance,data consistency,and stability,and the prototype presented here adopts a microservices architecture,breaking down the hardware into multiple subsystems and converting their functions into individual services.A central decision-making system leads the operations,supported by three auxiliary systems and three device control systems.Through inter-subsystem service calls,it achieves rapid imaging and spectroscopic monitoring.To verify system stability and observation efficiency,the system was tested on the Solar Full-disk Multi-layer Magnetograph.Experimental results verify this system can operate automatically for 4 consecutive months,acquire photospheric vector magnetic and Doppler velocity fields within a 15-minute interval,and measure chromospheric longitudinal magnetic and Doppler velocity fields in under 180 s.This ensures consistent and stable solar monitoring and serves as a practical methodological benchmark for the development of similar devices.展开更多
On the arrival of the 20 th anniversary of the journal,Research in Astronomy and Astrophysics(RAA),we see rapid progress in the frontiers of astronomy and astrophysics.To celebrate the birth and growth of RAA,a specia...On the arrival of the 20 th anniversary of the journal,Research in Astronomy and Astrophysics(RAA),we see rapid progress in the frontiers of astronomy and astrophysics.To celebrate the birth and growth of RAA,a special issue consisting of 11 invited reviews from more than 30 authors,mainly from China,has been organized.This is the second volume of the special issues entitled Frontiers in Astrophysics published in RAA.The publication aims at evaluating the current status and key progress in some frontier areas of astronomy and astrophysics with a spirit of guiding future studies.展开更多
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 ac...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.展开更多
The reflector system of the Five-hundred-meter Aperture Spherical radio Telescope （FAST） is designed to incorporate 4450 rigid panels supported by a flexible cable-net structure. The shapechanging operation that occ...The reflector system of the Five-hundred-meter Aperture Spherical radio Telescope （FAST） is designed to incorporate 4450 rigid panels supported by a flexible cable-net structure. The shapechanging operation that occurs in the process of observation will lead to a relative displacement between adjacent nodes in the cable-net. In addition, three nodes on a rigid panel are fixed with respect to each other. Thus, adaptive connecting mechanisms between panels and the cable-net are certainly needed. The present work focuses on the following aspects. Firstly, the degrees of freedom of adaptive connecting mechanisms were designed so that we can not only adapt the panel to the deformation of the cable- net, but also restrict the panel to its right place. Secondly, finite element and theoretical analyses were applied to calculate the scope of motion in adaptive connecting mechanisms during the cable-net＇s shape-changing operation, thus providing input parameters for the design size of the adaptive connecting mechanisms. In addition, the gap size between the panels is also investigated to solve the trade-off between avoiding panel collisions and increasing the observation efficiency of FAST.展开更多
The National Solar Observatory is currently developing the Accurate Infrared Magnetic Field Measurements of the Sun(AIMS). The primary mirror of the AIMS solar telescope is an off-axis parabolic with a diameter of 1 m...The National Solar Observatory is currently developing the Accurate Infrared Magnetic Field Measurements of the Sun(AIMS). The primary mirror of the AIMS solar telescope is an off-axis parabolic with a diameter of 1 m and with a large off-axis amount of 1 m. Due to the surface figure of the primary mirror under the used state is directly related to image quality of the whole system, a computer-generated hologram(CGH) is carried out to test the primary mirror, and the test results are used to polish the mirror to a higher surface accuracy. However, the fact that the distortion exists in the testing results leads to the failure of a further guide to deterministic optical processing. In this paper, a distortion correction method is proposed, which uses an orthogonal set of vector polynomials to mapping the coordinates of the mirror and the pixels of fringes, and then an interpolation method is adopted to obtain the corrected results. The testing accuracy by using CGH is also verified by an auto-collimate test experiment. According to the distorted corrected results, the root-mean-square of the surface figure is about 1/50λ(λ=632.8 nm) after polishing.展开更多
Radio Frequency System on Chip(RFSo C)offers great potential for implementing a complete next generation signal processing system on a single board for radio astronomy.We designed a pulsar digital backend system based...Radio Frequency System on Chip(RFSo C)offers great potential for implementing a complete next generation signal processing system on a single board for radio astronomy.We designed a pulsar digital backend system based on the ZCU111 board.The system uses RFSo C technology to implement digitization,channelization,correlation and high-speed data transmission in the Xilinx ZU28 DR device.We have evaluated the performance of the eight 12-bit RF-ADCs,which are integrated in RFSo C,with the maximum sampling rate of 4.096 GSPS.The RF-ADC sampling frequency,channel bandwidth and time resolution can be configured dynamically in our designed system.To verify the system performance,we deployed the RFSo C board on the Nanshan 26 m radio telescope and observed the pulsar signal with a frequency resolution of 1 MHz and time resolution of 64μs.In the observation test,we obtained pulsar profiles with high signal-to-noise ratio and accurately searched the DM values.The experimental results show that the performance of RF-ADCs,FPGA and CPU cores in RFSo C is sufficient for radio astronomy signal processing applications.展开更多
Mirror seeing will be one of the key factors influencing image quality of an extremely large ground-based optical telescope （ELT）. Computational fluid dynamics （CFD） can be used to estimate the mirror seeing and t...Mirror seeing will be one of the key factors influencing image quality of an extremely large ground-based optical telescope （ELT）. Computational fluid dynamics （CFD） can be used to estimate the mirror seeing and the effects of ventilation. In this paper, we present a simplified approach to simulation of mirror seeing for the Chinese Future Giant Telescope （CFGT, 30 m in diameter） with the CFD software ANSYS Icepak. We get the FWHM of the image and the distribution of refractive index structure function （CN2） above the mirror. We demonstrate that thermal control and ventilation are effective ways to improve the image quality. Our simulation results agree with those of other authors for the ELT. To reduce the mirror seeing to a level of 0.5＂, the suggested temperature excess of the primary mirror above the ambient air for thermal control of the CFGT is 0 - 2 K according to the present results of weakly forced convection. The limitations of the method are also discussed.展开更多
It is widely accepted that mirror seeing is caused by turbulent fluctuations in the index of air refraction in the vicinity of a telescope mirror. Computational Fluid Dynamics（CFD） is a useful tool to evaluate the e...It is widely accepted that mirror seeing is caused by turbulent fluctuations in the index of air refraction in the vicinity of a telescope mirror. Computational Fluid Dynamics（CFD） is a useful tool to evaluate the effects of mirror seeing. In this paper, we present a numerical method to estimate the mirror seeing for a large optical telescope（～ 4 m） in cases of natural convection with the ANSYS ICEPAK software. We get the FWHM of the image for different inclination angles（i） of the mirror and different temperature differences（△T） between the mirror and ambient air. Our results show that the mirror seeing depends very weakly on i, which agrees with observational data from the Canada-FranceHawaii Telescope. The numerical model can be used to estimate mirror seeing in the case of natural convection although with some limitations. We can determine △T for thermal control of the primary mirror according to the simulation, empirical data and site seeing.展开更多
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 a...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.展开更多
基金supported by the Investigation of Technological Infrastructure Resources(No.2023FY101101)the National Natural Science Foundation of China(NSFC)(No.11073027 and No.12373104)。
文摘Astronomical site selection work is very hard.Unmanned technologies are important trends and solutions.We present a relatively easy method to plan a high reliability site selection which can extend the time from site deployment to returning for maintaining by unmanned confirming the site.First,we redefine the reliability of a site selection deployment with the parameter of the trusty time,which means when we must return,and which can be relatively easy for estimating.The redefinition makes the reliability parameter as a Bayesian probability,and can be obtained by estimating besides testing,which makes the evaluation of each device's reliability much easier.Then we use block diagram tools in the Matlab Simulink software to construct structure diagram,and to link each component with relations of parallel,serial,protection,and so on.This makes the whole reliability value can be calculated at the time when we design or plan a site selection.We applied this concept and method in an actual site selection in Lenghu,Qinghai Province,China.The survey practice reveals its effectiveness and simpleness.
基金funded by the National Key Research and Development Program of China under Nos.2023YFA1608200&2020YFC2201703the National Natural Science Foundation of China(NSFC,Grant No.12020101002)the Natural Science Foundation of China for the youth under No.12103093。
文摘The proposed design of a microwave superconducting kinetic inductance detector(MKID)array readout system characterizes the performance of MKIDs through a digital homodyne frequency mixing architecture.Meanwhile,the readout system is implemented using a frequency division multiplexing circuit system,coupled with an FFT design to enable the readout of MKID arrays.The system is characterized by its compact size,low cost,portability,and ease of further development.Together,these features have significant implications for the design and readout of terahertz MKID arrays,while simultaneously advancing both the theoretical and practical aspects of MKID technology.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA0350300)the National Natural Science Foundation of China(12203105,12103091,62394351,12073008)the China Manned Space Project(CMS-CSST-2021-A12,CMS-CSST-2021-B10).
文摘The Wide Field Survey Telescope(WFST)is located at 4200 m on Saishiteng Mountain in Lenghu,Qinghai Province,China.It features a primary mirror with a diameter of 2.5 m and a camera equipped with nine CCDs,providing a wide field of view of approximately 3×3 square degrees.Calibration parameters are essential to ensure the precision of astrometric observations with the WFST.These parameters are derived from geometric distortion(GD)and gaps through astrometric modeling and are subsequently validated via the Yao’An High Precision Telescope(YAHPT).The GD solutions show maximum distortions between 1.18 and 10.29 pixels for the WFST chips,with central chips exhibiting lower distortion.After applying the GD correction,the precision of the WFST reaches 4 mas.The interchip gaps of the WFST range from 1.922 mm to 7.765 mm,corresponding to 10μm/pixel,aligning with the design and measurements.The calibrated parameters guarantee that the WFST can perform highly accurate astrometric measurements.Furthermore,as the WFST undergoes updates,the parameter model remains consistently applicable.
基金supported by National Key R&D Program of China(2023YFA1609700)Research and Education Integration Funding。
文摘This paper presents a comprehensive analysis of the photometric system of the University of Chinese Academy of Sciences 70 cm Telescope located at the Yan-qi Lake campus of the University of Chinese Academy of Sciences.We evaluated the linearity,bias stability,and dark current of the camera.Utilizing the Johnson-Cousins Blue-Visible-Red-Infrared filter system and an Andor DZ936 charge-coupled device camera,we conducted extensive observations of Landolt standard stars to determine the color terms,atmospheric extinction coefficients,photometric zero-points,and the sky background brightness.The results indicate that this telescope demonstrates excellent performance in photometric calibration and good system performance overall,meeting the requirements for limited scientific research and teaching purposes.
文摘We perform a time-resolved statistical study of GRB 221009A’s X-ray emission using Swift XRT Photon Counting and Windowed Timing data.After standard reduction(barycentric correction,pile-up,background subtraction via HEASOFT),we extracted light curves for each observational ID and for their aggregation.Countrate histograms were fitted using various statistical distributions;fit quality was assessed by chi-squared and the Bayesian Information Criterion.The first observational segment is best described by a Gaussian distribution(χ^(2)=68.4;BIC=7651.2),and the second by a Poisson distribution(χ^(2)=33.5;BIC=4413.3).When all segments are combined,the lognormal model provides the superior fit(χ^(2)=541.9;BIC=34365.5),indicating that the full data set’s count rates exhibit the skewness expected from a multiplicative process.These findings demonstrate that while individual time intervals conform to discrete or symmetric statistics,the collective emission profile across multiple observations is better captured by a lognormal distribution,consistent with complex,compounded variability in GRB afterglows.
基金Supported by National Key R&D Program of China(grant No.2023YFA1608304)Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0550103)National Natural Science Foundation of China(NSFC,grant No.11903054)。
文摘The SiTian Project represents a groundbreaking initiative in astronomy,aiming to deploy a global network of telescopes,each with a 1 m aperture,for comprehensive time-domain sky surveys.The network's innovative architecture features multiple observational nodes,each comprising three strategically aligned telescopes equipped with filters.This design enables three-color(g,r,i)channel imaging within each node,facilitating precise and coordinated observations.As a pathfinder to the full-scale project,the Mini-SiTian Project serves as the scientific and technological validation platform,utilizing three 30 cm aperture telescopes to validate the methodologies and technologies planned for the broader SiTian network.This paper focuses on the development and implementation of the Master Control System(MCS),and the central command hub for the Mini-SiTian Array.The MCS is designed to facilitate seamless communication with the SiTian Brain,the project's central processing and decisionmaking unit,while ensuring accurate task allocation,real-time status monitoring,and optimized observational workflows.The system adopts a robust architecture that separates front-end and back-end functionalities.A key innovation of the MCS is its ability to dynamically adjust observation plans in response to transient source alerts,enabling rapid and coordinated scans of target sky regions.The paper provides an in-depth analysis of the system's internal components,including the communication system,which is critical for seamless network operation.Extensive testing has validated the functionality,reliability,and compatibility of these components within the overall system architecture.The successful deployment of the MCS in managing the Mini-SiTian Array has demonstrated its practicality and efficacy in collaborative observation and distributed control.By simplifying cluster management and ensuring data integrity,the MCS represents a significant advancement in astronomical observation control systems.Its scalable and adaptable design not only supports the future expansion of the SiTian network but also provides a blueprint for other large-scale telescope arrays,marking a transformative step forward in time-domain astronomy.
基金supported by the Joint Research Fund in Astronomy(U1931130)under the cooperative agreement between the National Natural Science Foundation of China(NSFC)and the Chinese Academy of Sciences(CAS)support from NFSC(Grant Nos.11873010and 117330037)the Operation,Maintenance and Upgrading Fund for Astronomical Telescopes,and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administrated by the CAS。
文摘Dome A,Antarctica,has been thought to be one of the best astronomical sites on the Earth for decades.Since it was first visited by astronomers in 2008,dozens of facilities for astronomical observation and site testing were deployed.Due to its special geographical location,the data and message exchange between Dome A and the domestic control center could only depend on Iridium.Because the link bandwidth of Iridium is extremely limited,the network traffic cost is quite expensive and the network is rather unstable,the commonly used data transfer tools,such as rsync and scp,are not suitable in this case.In this paper,we design and implement a data transfer tool called NBFTP(narrow bandwidth file transfer protocol)for the astronomical observation of Dome A.NBFTP uses a uniform interface to arrange all types of data and matches specific transmission schemes for different data types according to rules.Break-point resuming and extensibility functions are also implemented.Our experimental results show that NBFTP consumes 60%less network traffic than rsync when detecting the data pending to be transferred.When transferring small files of 1 KB,the network traffic consumption of NBFTP is 40%less than rsync.However,as the file size increases,the network traffic consumption of NBFTP tends to approach rsync,but it is still smaller than rsync.
基金This work is supported by“the Fundamental Research Funds for the Central Universities”,111 project No.B20019Shanghai Natural Science Foundation,grant No.19ZR1466800.
文摘The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.
基金generously supported by the National Natural Science Foundation of China(NSFC,Grant Nos.12073047 and 12273077)the National Key Research and Development(Grant No.2022YFF0711500)。
文摘In this study,we conducted simulations to find the geometric aberrations expected for images taken by the Main Survey Camera of the Chinese Space Station Telescope(CSST)due to its motion.As anticipated by previous work,our findings indicate that the geometric distortion of light impacts the focal plane's apparent scale,with a more pronounced influence as the size of the focal plane increases.Our models suggest that the effect consistently influences the pixel scale in both the vertical and parallel directions.The apparent scale variation follows a sinusoidal distribution throughout one orbital period.Simulations reveal that the effect is particularly pronounced in the center of the Galaxy and gradually diminishes along the direction of ecliptic latitude.At low ecliptic latitudes,the total aberration leads to about a 0.94 pixel offset(a 20 minute exposure)and a 0.26 pixel offset(a 300 s exposure)at the edge of the field of view.Appropriate processings for the geometric effect during the CSST pre-and post-observation phases are presented.
基金funded by the National Key R&D Program of China under No.2022YFC2205300the National Natural Science Foundation of China(NSFC,grant Nos.12073067 and 11973078)the Chinese Academy of Sciences(CAS)“Light of West China”Program under No.2022-XBQNXZ012 and No.2020-XBQNXZ-018。
文摘We introduce the structure of a radio astronomy phased array feeds(PAF)beamforming demonstrator.In a laboratory environment,we have demonstrated beamforming on a received 1.25 GHz sinusoidal signal and used digital weighting techniques to plot the 2D pattern of the PAF.The radio frequency part of the demonstrator includes a 4×4 linearly polarized microstrip antenna array,all of which is connected in series with a low-noise amplifier.The signals from the central 4×2 array elements are injected into a radio frequency system-on-chip digital board,which can receive eight inputs with a bandwidth of 512 MHz.Combining the principle of undersampling,the beamforming is completed at a frequency of 1.25 GHz for the offline data,and a 2D image of the beam is plotted using beam scanning technology.
文摘The impact of structural stiffness on optical axis deviation poses a significant challenge in the design of equatorial telescope structures.A comprehensive analysis during the design process can reduce the reliance of a telescope on advanced control technologies,thereby improving its economic feasibility.Although full-system finite element analyses are reliable,they are encumbered by significant time requirements and limitations in covering all possible telescope orientations.Therefore,we propose an efficient and comprehensive analytical method to evaluate the optical axis deviation of equatorial telescopes across a full range of angles.To address the challenge of ensuring that the analysis covers all possible positions of an equatorial telescope,based on a model from SiTian project,we analyze the optical axis deviations caused by the fork arm at 25 different angles and then use fitting methods to obtain results for all angles.Based on the analysis results of the optical axis deviation caused by the stiffness of the optical tube in the horizontal position,we derive the results for the tube at any position using geometric relationships.Finally,we calculate the coupling factors and combine these impacts.Furthermore,we identify six discrete feature points to reflect possible telescope orientations and conduct comprehensive finite element analyses.The results are in alignment with those acquired through a comprehensive computational approach.
基金supported by the National Key R&D Program of China (2022YFF0503800)the Chinese Meridian Project,the National Natural Science Foundation of China (11427901)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA15320102)the Youth Innovation Promotion Association (2022057).
文摘With the growing significance of space weather forecasting,multi-layer magnetic and helioseismic telescopes are emerging as a key area of research.However,owing to the diverse operational processes and sophisticated hardware configurations of these devices,there is an urgent need for efficient autonomous observation capabilities.An autonomous Master Control System(MCS)can ensure efficient performance,data consistency,and stability,and the prototype presented here adopts a microservices architecture,breaking down the hardware into multiple subsystems and converting their functions into individual services.A central decision-making system leads the operations,supported by three auxiliary systems and three device control systems.Through inter-subsystem service calls,it achieves rapid imaging and spectroscopic monitoring.To verify system stability and observation efficiency,the system was tested on the Solar Full-disk Multi-layer Magnetograph.Experimental results verify this system can operate automatically for 4 consecutive months,acquire photospheric vector magnetic and Doppler velocity fields within a 15-minute interval,and measure chromospheric longitudinal magnetic and Doppler velocity fields in under 180 s.This ensures consistent and stable solar monitoring and serves as a practical methodological benchmark for the development of similar devices.
文摘On the arrival of the 20 th anniversary of the journal,Research in Astronomy and Astrophysics(RAA),we see rapid progress in the frontiers of astronomy and astrophysics.To celebrate the birth and growth of RAA,a special issue consisting of 11 invited reviews from more than 30 authors,mainly from China,has been organized.This is the second volume of the special issues entitled Frontiers in Astrophysics published in RAA.The publication aims at evaluating the current status and key progress in some frontier areas of astronomy and astrophysics with a spirit of guiding future studies.
基金supported by the National Natural Science Foundation of China(Grant No.11673039)the Open Project Program of the Key Laboratory of FAST,National Astronomical Observatories,Chinese Academy of Sciences
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos.11303059 and 11673039)the Chinese Academy of Sciences Youth Innovation Promotion Association+1 种基金CAS Key Technology Talent Programthe FAST FELLOWSHIP.The FAST FELLOWSHIP is supported by Special Funding for Advanced Users,budgeted and administrated by the Center for Astronomical MegaScience,Chinese Academy of Sciences(CAMS)
文摘The reflector system of the Five-hundred-meter Aperture Spherical radio Telescope （FAST） is designed to incorporate 4450 rigid panels supported by a flexible cable-net structure. The shapechanging operation that occurs in the process of observation will lead to a relative displacement between adjacent nodes in the cable-net. In addition, three nodes on a rigid panel are fixed with respect to each other. Thus, adaptive connecting mechanisms between panels and the cable-net are certainly needed. The present work focuses on the following aspects. Firstly, the degrees of freedom of adaptive connecting mechanisms were designed so that we can not only adapt the panel to the deformation of the cable- net, but also restrict the panel to its right place. Secondly, finite element and theoretical analyses were applied to calculate the scope of motion in adaptive connecting mechanisms during the cable-net＇s shape-changing operation, thus providing input parameters for the design size of the adaptive connecting mechanisms. In addition, the gap size between the panels is also investigated to solve the trade-off between avoiding panel collisions and increasing the observation efficiency of FAST.
基金funded by the West Light Foundation of the Chinese Academy of Sciences(Grant No.XAB2017B13)the National Natural Science Foundation of China(Grant No.11703072)。
文摘The National Solar Observatory is currently developing the Accurate Infrared Magnetic Field Measurements of the Sun(AIMS). The primary mirror of the AIMS solar telescope is an off-axis parabolic with a diameter of 1 m and with a large off-axis amount of 1 m. Due to the surface figure of the primary mirror under the used state is directly related to image quality of the whole system, a computer-generated hologram(CGH) is carried out to test the primary mirror, and the test results are used to polish the mirror to a higher surface accuracy. However, the fact that the distortion exists in the testing results leads to the failure of a further guide to deterministic optical processing. In this paper, a distortion correction method is proposed, which uses an orthogonal set of vector polynomials to mapping the coordinates of the mirror and the pixels of fringes, and then an interpolation method is adopted to obtain the corrected results. The testing accuracy by using CGH is also verified by an auto-collimate test experiment. According to the distorted corrected results, the root-mean-square of the surface figure is about 1/50λ(λ=632.8 nm) after polishing.
基金supported by the National Natural Science Foundation of China(Grant No.12073067)the program of the Light in China’s Western Region(2019-XBQNXZ-B-018)the Youth Innovation Promotion Association of CAS(2021059)。
文摘Radio Frequency System on Chip(RFSo C)offers great potential for implementing a complete next generation signal processing system on a single board for radio astronomy.We designed a pulsar digital backend system based on the ZCU111 board.The system uses RFSo C technology to implement digitization,channelization,correlation and high-speed data transmission in the Xilinx ZU28 DR device.We have evaluated the performance of the eight 12-bit RF-ADCs,which are integrated in RFSo C,with the maximum sampling rate of 4.096 GSPS.The RF-ADC sampling frequency,channel bandwidth and time resolution can be configured dynamically in our designed system.To verify the system performance,we deployed the RFSo C board on the Nanshan 26 m radio telescope and observed the pulsar signal with a frequency resolution of 1 MHz and time resolution of 64μs.In the observation test,we obtained pulsar profiles with high signal-to-noise ratio and accurately searched the DM values.The experimental results show that the performance of RF-ADCs,FPGA and CPU cores in RFSo C is sufficient for radio astronomy signal processing applications.
基金the support of the Large Scientific Equipments Repairing Project of Chinese Academy of Sciences:"Cooling Facility and Monitoring instruments for LAMOST Dome Seeing Improvement"
文摘Mirror seeing will be one of the key factors influencing image quality of an extremely large ground-based optical telescope （ELT）. Computational fluid dynamics （CFD） can be used to estimate the mirror seeing and the effects of ventilation. In this paper, we present a simplified approach to simulation of mirror seeing for the Chinese Future Giant Telescope （CFGT, 30 m in diameter） with the CFD software ANSYS Icepak. We get the FWHM of the image and the distribution of refractive index structure function （CN2） above the mirror. We demonstrate that thermal control and ventilation are effective ways to improve the image quality. Our simulation results agree with those of other authors for the ELT. To reduce the mirror seeing to a level of 0.5＂, the suggested temperature excess of the primary mirror above the ambient air for thermal control of the CFGT is 0 - 2 K according to the present results of weakly forced convection. The limitations of the method are also discussed.
基金support from the Guo Shou Jing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST)the Large Scientific Equipments Repairing Project of Chinese Academy of Sciences:"Cooling Facility and Monitoring Instruments for LAMOST Dome Seeing Improvement."supported by National Key Basic Research Program of China Y41J051N01
文摘It is widely accepted that mirror seeing is caused by turbulent fluctuations in the index of air refraction in the vicinity of a telescope mirror. Computational Fluid Dynamics（CFD） is a useful tool to evaluate the effects of mirror seeing. In this paper, we present a numerical method to estimate the mirror seeing for a large optical telescope（～ 4 m） in cases of natural convection with the ANSYS ICEPAK software. We get the FWHM of the image for different inclination angles（i） of the mirror and different temperature differences（△T） between the mirror and ambient air. Our results show that the mirror seeing depends very weakly on i, which agrees with observational data from the Canada-FranceHawaii Telescope. The numerical model can be used to estimate mirror seeing in the case of natural convection although with some limitations. We can determine △T for thermal control of the primary mirror according to the simulation, empirical data and site seeing.
基金funded by the Astronomical Joint Fund of the National Natural Science Foundation of China and Chinese Academy of Sciences (Grant Nos. U1831114, 11941002, and12073048)。
文摘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.
