VLBI(Very Long Baseline Interferometry)技术观测卫星需要对干涉测量数据进行相关和后处理,通过相关、时延校准、条纹搜索,最终得到卫星的基线几何时延.基于天文开源软件建立起一套卫星干涉测量数据处理系统.该系统可工作在实时和事...VLBI(Very Long Baseline Interferometry)技术观测卫星需要对干涉测量数据进行相关和后处理,通过相关、时延校准、条纹搜索,最终得到卫星的基线几何时延.基于天文开源软件建立起一套卫星干涉测量数据处理系统.该系统可工作在实时和事后两种状态,实现相关、中性大气、电离层、钟模型以及仪器硬件的时延校准、条纹搜索、生成基线时延和时延率序列.使用该系统处理北斗GEO(Geosynchronous Earth Orbit)卫星的干涉测量试验数据,得到了精度在1-2 ns量级的卫星基线时延序列.展开更多
平方公里阵列(Square Kilometre Array,SKA)项目是建设全球最大射电望远镜的国际合作项目,其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级.连续谱巡天是SKA的主要观测模式之一,基于连续谱成像建立巡天区域的标准星图,...平方公里阵列(Square Kilometre Array,SKA)项目是建设全球最大射电望远镜的国际合作项目,其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级.连续谱巡天是SKA的主要观测模式之一,基于连续谱成像建立巡天区域的标准星图,将能为后续天文科学研究奠定重要基础.银河系与河外星系全天默奇森宽场阵列拓展巡天(GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended,GLEAM-X)是2018--2020年利用SKA先导望远镜默奇森宽场阵列(Murchison Wide-field Array,MWA)二期拓展阵列开展的新的射电连续谱巡天项目,观测期间积累了大量的低频巡天观测数据.海量观测数据的自动化、大批量处理是SKA望远镜项目所面临的的最大挑战和难题之一,基于分布式执行框架的成像管线优化经验将有助于解决海量数据处理问题.详细介绍了GLEAM-X成像管线并对其进行整合和改进,在中国SKA区域中心原型机(China SKA Regional Centre Prototype,CSRC-P)上实现了多条管线并行处理,使用GLEAM-X观测数据验证成像管线系统的部署和测试其正确性.随后为了优化管线提高处理效率,使用数据激活流图形引擎(Data Activated Liu Graph Engine,DALiuGE),将成像管线集成入DALiuGE执行框架中实现了管线的自动化分布式并行处理.通过性能测试与结果分析表明,基于DALiuGE执行框架进行优化的成像管线相较于传统的并行方式具有更好的性能优势、更灵活的适配性和可扩展性,可支持未来SKA第一阶段试运行期间的大规模连续谱成像实验.展开更多
低频射电望远镜阵列宽视场成像正面临着一系列难点问题,其中最关键的问题是非共面基线效应.它的存在使得忽略w项将导致最终图像出现畸变,且随着视场的增大而加重.综述并剖析了几种w项改正算法及其技术原理,并分析了它们的计算成本和计...低频射电望远镜阵列宽视场成像正面临着一系列难点问题,其中最关键的问题是非共面基线效应.它的存在使得忽略w项将导致最终图像出现畸变,且随着视场的增大而加重.综述并剖析了几种w项改正算法及其技术原理,并分析了它们的计算成本和计算复杂度,进而分析比较了它们的优缺点.以平方公里阵(Square Kilometre Array,SKA)射电望远镜第1阶段低频阵列为研究对象,选取faceting和w-projection成像算法进行了仿真实验.与传统的二维傅立叶变换成像算法进行对比,分析了它们的成像质量和正确性,结果表明这两种算法在宽视场成像方面均明显优于二维傅立叶变换方法.还具体分析了分面(facet)的数目对faceting成像质量和运行时间的影响,以及w步数对w-projection成像质量和运行时间的影响,表明facet数目和w步数的选择必须合理.最后,分析了数据量大小对这两种成像算法运行时间的影响,表明这两种算法在进行海量数据处理前,需要作算法优化改进.研究结果为后续进一步综合分析宽视场成像技术以及这些技术的实用性研究提供了有价值的参考.展开更多
对2021年VLBI (Very Long Baseline Interferometry)全球观测系统(VLBI Global Observing System,VGOS)单基线开展的1 h世界时(Universal Time, UT1)加强观测数据进行分析,结果表明, VGOS单基线测得的UT1与IERS (International Earth Ro...对2021年VLBI (Very Long Baseline Interferometry)全球观测系统(VLBI Global Observing System,VGOS)单基线开展的1 h世界时(Universal Time, UT1)加强观测数据进行分析,结果表明, VGOS单基线测得的UT1与IERS (International Earth Rotation Service) C04序列提供的UT1之差的RMS (Root Mean Square)为25.3μs,优于传统S/X双频段UT1加强观测(Intensive observation, INT1)试验的28.2μs,且UT1的平均形式精度提高1倍.因VGOS单基线1 h观测数目比INT1多1倍,其测得的UT1受极移误差的影响更加稳定,每100μas的极移误差将对UT1引入2.8μs的偏移.此外分析了VGOS 30 min观测数据,除平均形式精度变差外, UT1测量结果与1 h结果相当,表明VGOS单基线30 min观测可用于UT1的超快速服务.同时分析和评估了2021年国内佘山与南山13 m VGOS基线的UT1加强观测能力,统计得到8次观测的RMS为46.2μs,平均形式误差为17.7μs,相比佘山25 m和南山25 m天线的S/X双频观测有显著提升.展开更多
Advanced testing methods for the dynamics of mechanical microdevices are necessary to develop reliable, marketable microelectromechanical systems. A system for measuring the nanometer motions of microscopic structures...Advanced testing methods for the dynamics of mechanical microdevices are necessary to develop reliable, marketable microelectromechanical systems. A system for measuring the nanometer motions of microscopic structures has been demonstrated. Stop-action images of a target have been obtained with computer microvision, microscopic interferometry, and stroboscopic illuminator. It can be developed for measuring the in-plane-rigid-body motions, surface shapes, out-of-plane motions and deformations of microstructures. A new algorithm of sub-pixel step length correlation template matching is proposed to extract the in-plane displacement from vision images. Hariharan five-step phase-shift interferometry algorithm and unwrapping algorithms are adopted to measure the out-of-plane motions. It is demonstrated that the system can measure the motions of solder wetting in surface mount technology(SMT).展开更多
Micro-structures 3-D profile measurement is an important measurement content for research on micro-machining and characterization of micro-dimension. In this paper,a new method involved 2-D structure template, which g...Micro-structures 3-D profile measurement is an important measurement content for research on micro-machining and characterization of micro-dimension. In this paper,a new method involved 2-D structure template, which guides phase unwrapping,is proposed based on phase-shifting microscopic interferometry.It is fit not only for static measurement, but also for dynamic measurement,especially for motion of MEMS devices.3-D profile of active comb of micro-resonator is obtained by using the method.The theoretic precision in out-of-plane direction is better than 0.5 nm.The in-plane theoretic precision in micro-structures is better than 0.5 μm.But at the edge of micro-structures,it is on the level of micrometer mainly caused by imprecise edge analysis.Finally,its disadvantages and the following development are discussed.展开更多
Geometrical features of micro-systems can be determined by either tactile or optical profiling techniques, which show different non-linear transfer characteristics. This has to be considered especially, if the instrum...Geometrical features of micro-systems can be determined by either tactile or optical profiling techniques, which show different non-linear transfer characteristics. This has to be considered especially, if the instruments operate close to their physical limitations. Depending on the specific measuring task either point-wise or areal optical measurement may be advantageous. Hence, examples for both approaches are discussed. Furthermore, systematic effects, which are related to the measuring principle have to be taken into account, e.g. if sharp edges or slopes are present on the measuring object. As it is shown, for white-light interferometry these difficulties can be solved by a two-wavelength technique.展开更多
Structures of slender shape, like guyed masts, chimneys or TV towers, are exposed to the excitation of dynamic movements. The most common cause of vibration is the wind that reduces generation of vortices. Another imp...Structures of slender shape, like guyed masts, chimneys or TV towers, are exposed to the excitation of dynamic movements. The most common cause of vibration is the wind that reduces generation of vortices. Another important reason is a sudden strike from seismic or para-seismic forces. Structure exposed to wind impact is subjected to harmonically various force, perpendicular to the air stream, which is an effect of vortices, shedding on alternate sides of slructure. Because of the possibility of vibration the damping of a structure has to be designed. Measuring of decay in the oscillation allows to find the logarithmic decrement of the real structure and compare it with the designed value. Apart from damping, the proper designing of tall slender structures has to preserve the significant difference between vortex shedding frequencies and the natural frequencies of the structure shape modes. In the case of guyed masts it is important to analyse the response of a real structure to the exceptional dynamic load, such as a sudden break of guy or fall off a load from a structure, e.g., icing or antennas. The dynamic analysis of a real slructure requires the accurate values describing the dynamic behavior of tall structures （e.g., amplitudes）. The accuracy of 0.1 mm is provided by ground-based interferometric radar. This device is a part of the IBIS-S （image by interferometric survey） system, which calculates the displacement values on the basis of the difference between phases of waves received in consecutive samples. Typically, the measurements of tall structures are performed with several sensors （strain gauges, accelerometers）. Instead, the IBIS-S system allows the quasi-continuous （not limited to points） observation of the entire structure without installation of any sensors or reflectors. The real resolution （along the structure）, which means the minimum distance between two observed points, amounts up to about 0.7 m,展开更多
This paper reviews some of the key enabling technologies for advanced and future laser interferometer gravitational wave detectors, which must combine test masses with the lowest possible optical and acoustic losses, ...This paper reviews some of the key enabling technologies for advanced and future laser interferometer gravitational wave detectors, which must combine test masses with the lowest possible optical and acoustic losses, with high stability lasers and various techniques for suppressing noise. Sect. 1 of this paper presents a review of the acoustic properties of test masses. Sect. 2 reviews the technology of the amorphous dielectric coatings which are currently universally used for the mirrors in advanced laser interferometers, but for which lower acoustic loss would be very advantageous. In sect. 3 a new generation of crystalline optical coatings that offer a substantial reduction in thermal noise is reviewed. The optical properties of test masses are reviewed in sect. 4, with special focus on the properties of silicon, an important candidate material for future detectors. Sect. 5 of this paper presents the very low noise, high stability laser technology that underpins all advanced and next generation laser interferometers.展开更多
High-resolution observations of high-redshift(z > 4) radio quasars offer a unique insight into jet kinematics at early cosmological epochs, as well as constraints on cosmological model parameters.Due to the general...High-resolution observations of high-redshift(z > 4) radio quasars offer a unique insight into jet kinematics at early cosmological epochs, as well as constraints on cosmological model parameters.Due to the general weakness of extremely distant objects and the apparently slow structural changes caused by cosmological time dilation, only a couple of high-redshift quasars(HRQs) have been studied with parsec-scale resolutions, and with limited number of observing epochs. Here we report on very long baseline interferometry(VLBI) observations of a high-redshift blazar J1430 + 4204(z=4.72) in the 8 GHz frequency band at five different epochs spanning 22 years. The source shows a compact core–jet structure with two jet components being identified within 3 milli-arcsecond(mas) scale. The long time span and multiple-epoch data allow for the kinematic studies of the jet components. That results in a jet proper motion of μ(J1) = 0.017 ± 0.002 mas a^-1 and μ(J2) = 0.156 ± 0.015 mas a^-1, respectively. For the fastest-moving outer jet component J2, the corresponding apparent transverse speed is (19.5 ± 1.9) c.The inferred bulk jet Lorentz factor C=14.6 ± 3.8 and viewing angle θ=2.2°± 1.6°indicate highly relativistic beaming. The Lorentz factor and apparent proper motion are the highest measured to date among the z > 4 jetted radio sources, while the jet kinematics is still consistent with the cosmological interpretation of quasar redshifts.展开更多
A Michelson interferometer based sensor, to monitor the displacement and vibration of a surface, is presented. The interference signals detected in quadrature are processed using analog electronics to find the directi...A Michelson interferometer based sensor, to monitor the displacement and vibration of a surface, is presented. The interference signals detected in quadrature are processed using analog electronics to find the direction of the motion of a vibrating surface in real-time. The complete instrumentation and signal processing are implemented for the interpretation of the amplitude as well as positive and negative excursion of the vibration cycles. This new technique is simpler as compared to the techniques commonly used in the interferometer based vibration sensors. Using this technique, we have measured mechanical vibrations having a magnitude of the order of nanometers and frequency in the range of 50Hz to 500Hz. By making small changes in the electronic circuit, the technique can be implemented for the extended range of the vibration frequencies and amplitude.展开更多
We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications （e.g. military, counter terrorist, and customs authorities in protecting ports and harbors）, off...We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications （e.g. military, counter terrorist, and customs authorities in protecting ports and harbors）, offshore production facilities or coastal approaches as well as various marine applications. In this paper, we propose a new approach to underwater sonar systems using the voltage-controlled liquid crystals and simple multiplexing method. The proposed method permits measurement of sound under water at multiple points along an optical fiber using the low cost components and standard single mode fiber, without complex interferometric measurement techniques, electronics or demodulation software.展开更多
文摘平方公里阵列(Square Kilometre Array,SKA)项目是建设全球最大射电望远镜的国际合作项目,其灵敏度和测量速度将比当前所有的射电望远镜都要高出一个数量级.连续谱巡天是SKA的主要观测模式之一,基于连续谱成像建立巡天区域的标准星图,将能为后续天文科学研究奠定重要基础.银河系与河外星系全天默奇森宽场阵列拓展巡天(GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended,GLEAM-X)是2018--2020年利用SKA先导望远镜默奇森宽场阵列(Murchison Wide-field Array,MWA)二期拓展阵列开展的新的射电连续谱巡天项目,观测期间积累了大量的低频巡天观测数据.海量观测数据的自动化、大批量处理是SKA望远镜项目所面临的的最大挑战和难题之一,基于分布式执行框架的成像管线优化经验将有助于解决海量数据处理问题.详细介绍了GLEAM-X成像管线并对其进行整合和改进,在中国SKA区域中心原型机(China SKA Regional Centre Prototype,CSRC-P)上实现了多条管线并行处理,使用GLEAM-X观测数据验证成像管线系统的部署和测试其正确性.随后为了优化管线提高处理效率,使用数据激活流图形引擎(Data Activated Liu Graph Engine,DALiuGE),将成像管线集成入DALiuGE执行框架中实现了管线的自动化分布式并行处理.通过性能测试与结果分析表明,基于DALiuGE执行框架进行优化的成像管线相较于传统的并行方式具有更好的性能优势、更灵活的适配性和可扩展性,可支持未来SKA第一阶段试运行期间的大规模连续谱成像实验.
文摘低频射电望远镜阵列宽视场成像正面临着一系列难点问题,其中最关键的问题是非共面基线效应.它的存在使得忽略w项将导致最终图像出现畸变,且随着视场的增大而加重.综述并剖析了几种w项改正算法及其技术原理,并分析了它们的计算成本和计算复杂度,进而分析比较了它们的优缺点.以平方公里阵(Square Kilometre Array,SKA)射电望远镜第1阶段低频阵列为研究对象,选取faceting和w-projection成像算法进行了仿真实验.与传统的二维傅立叶变换成像算法进行对比,分析了它们的成像质量和正确性,结果表明这两种算法在宽视场成像方面均明显优于二维傅立叶变换方法.还具体分析了分面(facet)的数目对faceting成像质量和运行时间的影响,以及w步数对w-projection成像质量和运行时间的影响,表明facet数目和w步数的选择必须合理.最后,分析了数据量大小对这两种成像算法运行时间的影响,表明这两种算法在进行海量数据处理前,需要作算法优化改进.研究结果为后续进一步综合分析宽视场成像技术以及这些技术的实用性研究提供了有价值的参考.
文摘Advanced testing methods for the dynamics of mechanical microdevices are necessary to develop reliable, marketable microelectromechanical systems. A system for measuring the nanometer motions of microscopic structures has been demonstrated. Stop-action images of a target have been obtained with computer microvision, microscopic interferometry, and stroboscopic illuminator. It can be developed for measuring the in-plane-rigid-body motions, surface shapes, out-of-plane motions and deformations of microstructures. A new algorithm of sub-pixel step length correlation template matching is proposed to extract the in-plane displacement from vision images. Hariharan five-step phase-shift interferometry algorithm and unwrapping algorithms are adopted to measure the out-of-plane motions. It is demonstrated that the system can measure the motions of solder wetting in surface mount technology(SMT).
基金Supported:Tianjin Important Science and Technology Project(043185911) National High-Technology Research and De-velopment Project (863 project) in China (2004AA404042) .
文摘Micro-structures 3-D profile measurement is an important measurement content for research on micro-machining and characterization of micro-dimension. In this paper,a new method involved 2-D structure template, which guides phase unwrapping,is proposed based on phase-shifting microscopic interferometry.It is fit not only for static measurement, but also for dynamic measurement,especially for motion of MEMS devices.3-D profile of active comb of micro-resonator is obtained by using the method.The theoretic precision in out-of-plane direction is better than 0.5 nm.The in-plane theoretic precision in micro-structures is better than 0.5 μm.But at the edge of micro-structures,it is on the level of micrometer mainly caused by imprecise edge analysis.Finally,its disadvantages and the following development are discussed.
文摘Geometrical features of micro-systems can be determined by either tactile or optical profiling techniques, which show different non-linear transfer characteristics. This has to be considered especially, if the instruments operate close to their physical limitations. Depending on the specific measuring task either point-wise or areal optical measurement may be advantageous. Hence, examples for both approaches are discussed. Furthermore, systematic effects, which are related to the measuring principle have to be taken into account, e.g. if sharp edges or slopes are present on the measuring object. As it is shown, for white-light interferometry these difficulties can be solved by a two-wavelength technique.
文摘Structures of slender shape, like guyed masts, chimneys or TV towers, are exposed to the excitation of dynamic movements. The most common cause of vibration is the wind that reduces generation of vortices. Another important reason is a sudden strike from seismic or para-seismic forces. Structure exposed to wind impact is subjected to harmonically various force, perpendicular to the air stream, which is an effect of vortices, shedding on alternate sides of slructure. Because of the possibility of vibration the damping of a structure has to be designed. Measuring of decay in the oscillation allows to find the logarithmic decrement of the real structure and compare it with the designed value. Apart from damping, the proper designing of tall slender structures has to preserve the significant difference between vortex shedding frequencies and the natural frequencies of the structure shape modes. In the case of guyed masts it is important to analyse the response of a real structure to the exceptional dynamic load, such as a sudden break of guy or fall off a load from a structure, e.g., icing or antennas. The dynamic analysis of a real slructure requires the accurate values describing the dynamic behavior of tall structures （e.g., amplitudes）. The accuracy of 0.1 mm is provided by ground-based interferometric radar. This device is a part of the IBIS-S （image by interferometric survey） system, which calculates the displacement values on the basis of the difference between phases of waves received in consecutive samples. Typically, the measurements of tall structures are performed with several sensors （strain gauges, accelerometers）. Instead, the IBIS-S system allows the quasi-continuous （not limited to points） observation of the entire structure without installation of any sensors or reflectors. The real resolution （along the structure）, which means the minimum distance between two observed points, amounts up to about 0.7 m,
基金financial support during The Next Detectors for Gravitational Wave Astronomy workshop in Beijing in 2015
文摘This paper reviews some of the key enabling technologies for advanced and future laser interferometer gravitational wave detectors, which must combine test masses with the lowest possible optical and acoustic losses, with high stability lasers and various techniques for suppressing noise. Sect. 1 of this paper presents a review of the acoustic properties of test masses. Sect. 2 reviews the technology of the amorphous dielectric coatings which are currently universally used for the mirrors in advanced laser interferometers, but for which lower acoustic loss would be very advantageous. In sect. 3 a new generation of crystalline optical coatings that offer a substantial reduction in thermal noise is reviewed. The optical properties of test masses are reviewed in sect. 4, with special focus on the properties of silicon, an important candidate material for future detectors. Sect. 5 of this paper presents the very low noise, high stability laser technology that underpins all advanced and next generation laser interferometers.
基金This work was supported by the National Key R&D Programme of China(2018YFA0404603)the Chinese Academy of Sciences(114231KYSB20170003)+1 种基金the Hungarian National Research,Development and Innovation Office(2018-2.1.14-T T-CN-2018-00001).The authors acknowledge the use of Astrogeo Center database of brightness distributions,correlated flux densitiesimages of compact radio sources produced with VLBI.YZ thanks Shu Fengchun,Alexey Melnikov,Jamie McCallum,and Bo Xia for providing the Asia-Oceania VLBI(AOV)data and auxiliary telescope system temperature files.
文摘High-resolution observations of high-redshift(z > 4) radio quasars offer a unique insight into jet kinematics at early cosmological epochs, as well as constraints on cosmological model parameters.Due to the general weakness of extremely distant objects and the apparently slow structural changes caused by cosmological time dilation, only a couple of high-redshift quasars(HRQs) have been studied with parsec-scale resolutions, and with limited number of observing epochs. Here we report on very long baseline interferometry(VLBI) observations of a high-redshift blazar J1430 + 4204(z=4.72) in the 8 GHz frequency band at five different epochs spanning 22 years. The source shows a compact core–jet structure with two jet components being identified within 3 milli-arcsecond(mas) scale. The long time span and multiple-epoch data allow for the kinematic studies of the jet components. That results in a jet proper motion of μ(J1) = 0.017 ± 0.002 mas a^-1 and μ(J2) = 0.156 ± 0.015 mas a^-1, respectively. For the fastest-moving outer jet component J2, the corresponding apparent transverse speed is (19.5 ± 1.9) c.The inferred bulk jet Lorentz factor C=14.6 ± 3.8 and viewing angle θ=2.2°± 1.6°indicate highly relativistic beaming. The Lorentz factor and apparent proper motion are the highest measured to date among the z > 4 jetted radio sources, while the jet kinematics is still consistent with the cosmological interpretation of quasar redshifts.
文摘A Michelson interferometer based sensor, to monitor the displacement and vibration of a surface, is presented. The interference signals detected in quadrature are processed using analog electronics to find the direction of the motion of a vibrating surface in real-time. The complete instrumentation and signal processing are implemented for the interpretation of the amplitude as well as positive and negative excursion of the vibration cycles. This new technique is simpler as compared to the techniques commonly used in the interferometer based vibration sensors. Using this technique, we have measured mechanical vibrations having a magnitude of the order of nanometers and frequency in the range of 50Hz to 500Hz. By making small changes in the electronic circuit, the technique can be implemented for the extended range of the vibration frequencies and amplitude.
文摘We describe a fiber optic hydrophone array system that could be used for underwater acoustic surveillance applications （e.g. military, counter terrorist, and customs authorities in protecting ports and harbors）, offshore production facilities or coastal approaches as well as various marine applications. In this paper, we propose a new approach to underwater sonar systems using the voltage-controlled liquid crystals and simple multiplexing method. The proposed method permits measurement of sound under water at multiple points along an optical fiber using the low cost components and standard single mode fiber, without complex interferometric measurement techniques, electronics or demodulation software.
