Hard X-ray Imager(HXI)is one of the three scientific instruments onboard the Advanced Spacebased Solar Observatory(ASO-S)mission,which is proposed for the 25th solar maximum by the Chinese solar community.HXI is desig...Hard X-ray Imager(HXI)is one of the three scientific instruments onboard the Advanced Spacebased Solar Observatory(ASO-S)mission,which is proposed for the 25th solar maximum by the Chinese solar community.HXI is designed to investigate the non-thermal high-energy electrons accelerated in solar flares by providing images of solar flaring regions in the energy range from 30 keV to 200 keV.The imaging principle of HXI is based on spatially modulated Fourier synthesis and utilizes about 91 sets of bi-grid sub-collimators and corresponding LaBr3 detectors to obtain Fourier components with a spatial resolution of about 3 arcsec and a time resolution better than 0.5 s.An engineering prototype has been developed and tested to verify the feasibility of design.In this paper,we present background,instrument design and the development and test status of the prototype.展开更多
The Large sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST)is a Chinese national scientific research facility operated by National Astronomical Observatories,Chinese Academy of Sciences(NAOC).The LAMOST surv...The Large sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST)is a Chinese national scientific research facility operated by National Astronomical Observatories,Chinese Academy of Sciences(NAOC).The LAMOST survey for the Milky Way Galaxy and extra-galactic objects has been carried out for several years.The accuracies in measuring radial velocity are expected to be 5 km s-1 for the low resolution spectroscopic survey(R=1800),and 1 km s-1 for the medium resolution mode.The stability of spectrograph is the main factor affecting the accuracies in measuring radial velocity,so an Active Flexure Compensation Method(AFCM)based on Back Propagation Neural Network(BPNN)is proposed in this paper.It utilizes a deep BP(4-layer,5-layer etc.)model of thermal-induced flexure to periodically predict and apply flexure corrections by commanding the corresponding tilt and tip motions to the camera.The spectrograph camera system is adjusted so that the positions of these spots match those in a reference image.The simulated calibration of this compensation method analytically illustrates its performance on LAMOST spectrograph.展开更多
Transmission efficiency(TE) and focal ratio degradation(FRD) are two important parameters for evaluating the quality of an optical fiber system used for astronomy. Compared to TE, the focal ratio is more easily influe...Transmission efficiency(TE) and focal ratio degradation(FRD) are two important parameters for evaluating the quality of an optical fiber system used for astronomy. Compared to TE, the focal ratio is more easily influenced by external factors, such as bending or stress. Optical cables are widely implemented for multi-object telescopes and integral field units(IFUs). The design and fabrication process of traditional optical cables seldom considers the requirements of astronomical applications. In this paper, we describe a fiber bundle structure as the basic unit for miniaturized high-density FASOT-IFU optical cables,instead of the micro-tube structure in stranded cables. Seven fibers with hexagonal arrangement were accurately positioned by ultraviolet(UV)-curing acrylate to form the bundle. The coating diameter of a fiber is0.125 mm, and the outer diameter of the bundle is 0.58 mm. Compared with the 0.8 mm micro-tube structure of a traditional stranded cable, the outer diameter of the fiber bundle was reduced by 27.5%. Fiber paste was filled into the bundle to reduce stress between the fibers. We tested the output focal ratio(OFR) in95% of the encircled energy(EE95) of the fibers in the bundle under different conditions. With the incident focal ratio F/8, the maximum difference of OFR is 0.6. In particular, when the incident focal ratio is F/5,the maximum difference of OFR is only 0.1. The jacket formed by the UV-curing acrylate can withstand a certain stress of less than 1.38 N mm-1. The fiber bundle can maintain uniform emitting characteristics with a bending radius of 7.5 cm and with tension less than 6 N. The test results show that the structure of the fiber bundle can be used as a basic unit for miniaturized high-density astronomical optical cables.展开更多
In this paper we illustrate the technique used by the New Vacuum Solar Telescope（NVST）to increase the spatial resolution of two-dimensional（2D）solar spectroscopy observations involving two dimensions of space and ...In this paper we illustrate the technique used by the New Vacuum Solar Telescope（NVST）to increase the spatial resolution of two-dimensional（2D）solar spectroscopy observations involving two dimensions of space and one of wavelength.Without an image stabilizer at the NVST,large scale wobble motion is present during the spatial scanning,whose instantaneous amplitude can reach 1.3′′due to the Earth’s atmosphere and the precision of the telescope guiding system,and seriously decreases the spatial resolution of 2D spatial maps composed with scanned spectra.We make the following effort to resolve this problem：the imaging system（e.g.,the Ti O-band）is used to record and detect the displacement vectors of solar image motion during the raster scan,in both the slit and scanning directions.The spectral data（e.g.,the Hαline）which are originally obtained in time sequence are corrected and re-arranged in space according to those displacement vectors.Raster scans are carried out in several active regions with different seeing conditions（two rasters are illustrated in this paper）.Given a certain spatial sampling and temporal resolution,the spatial resolution of the composed 2D map could be close to that of the slit-jaw image.The resulting quality after correction is quantitatively evaluated with two methods.A physical quantity,such as the line-of-sight velocities in multiple layers of the solar atmosphere,is also inferred from the re-arranged spectrum,demonstrating the advantage of this technique.展开更多
基金supported by the Strategic Priority Research Program on Space Science, Chinese Academy of Sciences (Grant No. XDA15320104)the National Natural Science Foundation of China (Grant Nos. 11427803, 11622327, 11703079, 11803093 and 11820101002)
文摘Hard X-ray Imager(HXI)is one of the three scientific instruments onboard the Advanced Spacebased Solar Observatory(ASO-S)mission,which is proposed for the 25th solar maximum by the Chinese solar community.HXI is designed to investigate the non-thermal high-energy electrons accelerated in solar flares by providing images of solar flaring regions in the energy range from 30 keV to 200 keV.The imaging principle of HXI is based on spatially modulated Fourier synthesis and utilizes about 91 sets of bi-grid sub-collimators and corresponding LaBr3 detectors to obtain Fourier components with a spatial resolution of about 3 arcsec and a time resolution better than 0.5 s.An engineering prototype has been developed and tested to verify the feasibility of design.In this paper,we present background,instrument design and the development and test status of the prototype.
基金support of the National Natural Science Foundation of China(Grant No.11503005)Jiangsu Students’ Innovation and Entrepreneurship Training Program(201910294155Y and 201810294059X)the National Undergraduate Training Program for Innovation and Entrepreneurship(201810294099).
文摘The Large sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST)is a Chinese national scientific research facility operated by National Astronomical Observatories,Chinese Academy of Sciences(NAOC).The LAMOST survey for the Milky Way Galaxy and extra-galactic objects has been carried out for several years.The accuracies in measuring radial velocity are expected to be 5 km s-1 for the low resolution spectroscopic survey(R=1800),and 1 km s-1 for the medium resolution mode.The stability of spectrograph is the main factor affecting the accuracies in measuring radial velocity,so an Active Flexure Compensation Method(AFCM)based on Back Propagation Neural Network(BPNN)is proposed in this paper.It utilizes a deep BP(4-layer,5-layer etc.)model of thermal-induced flexure to periodically predict and apply flexure corrections by commanding the corresponding tilt and tip motions to the camera.The spectrograph camera system is adjusted so that the positions of these spots match those in a reference image.The simulated calibration of this compensation method analytically illustrates its performance on LAMOST spectrograph.
基金funded by the Joint Research Fund in Astronomy under cooperative agreement between the National Natural Science Foundation of China (NSFC)the Chinese Academy of Sciences (Grant Nos. U1631239 and U1831115)+1 种基金the NSFC (Grant No. 11603008)the Fundamental Research Funds for Central Universities to Harbin Engineering University
文摘Transmission efficiency(TE) and focal ratio degradation(FRD) are two important parameters for evaluating the quality of an optical fiber system used for astronomy. Compared to TE, the focal ratio is more easily influenced by external factors, such as bending or stress. Optical cables are widely implemented for multi-object telescopes and integral field units(IFUs). The design and fabrication process of traditional optical cables seldom considers the requirements of astronomical applications. In this paper, we describe a fiber bundle structure as the basic unit for miniaturized high-density FASOT-IFU optical cables,instead of the micro-tube structure in stranded cables. Seven fibers with hexagonal arrangement were accurately positioned by ultraviolet(UV)-curing acrylate to form the bundle. The coating diameter of a fiber is0.125 mm, and the outer diameter of the bundle is 0.58 mm. Compared with the 0.8 mm micro-tube structure of a traditional stranded cable, the outer diameter of the fiber bundle was reduced by 27.5%. Fiber paste was filled into the bundle to reduce stress between the fibers. We tested the output focal ratio(OFR) in95% of the encircled energy(EE95) of the fibers in the bundle under different conditions. With the incident focal ratio F/8, the maximum difference of OFR is 0.6. In particular, when the incident focal ratio is F/5,the maximum difference of OFR is only 0.1. The jacket formed by the UV-curing acrylate can withstand a certain stress of less than 1.38 N mm-1. The fiber bundle can maintain uniform emitting characteristics with a bending radius of 7.5 cm and with tension less than 6 N. The test results show that the structure of the fiber bundle can be used as a basic unit for miniaturized high-density astronomical optical cables.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11773072, 11573012 and 11473064)
文摘In this paper we illustrate the technique used by the New Vacuum Solar Telescope（NVST）to increase the spatial resolution of two-dimensional（2D）solar spectroscopy observations involving two dimensions of space and one of wavelength.Without an image stabilizer at the NVST,large scale wobble motion is present during the spatial scanning,whose instantaneous amplitude can reach 1.3′′due to the Earth’s atmosphere and the precision of the telescope guiding system,and seriously decreases the spatial resolution of 2D spatial maps composed with scanned spectra.We make the following effort to resolve this problem：the imaging system（e.g.,the Ti O-band）is used to record and detect the displacement vectors of solar image motion during the raster scan,in both the slit and scanning directions.The spectral data（e.g.,the Hαline）which are originally obtained in time sequence are corrected and re-arranged in space according to those displacement vectors.Raster scans are carried out in several active regions with different seeing conditions（two rasters are illustrated in this paper）.Given a certain spatial sampling and temporal resolution,the spatial resolution of the composed 2D map could be close to that of the slit-jaw image.The resulting quality after correction is quantitatively evaluated with two methods.A physical quantity,such as the line-of-sight velocities in multiple layers of the solar atmosphere,is also inferred from the re-arranged spectrum,demonstrating the advantage of this technique.
