Extreme ultraviolet(EUV)observations are widely used in solar activity research and space weather forecasting since they can observe both the solar eruptions and the source regions of the solar wind.Flat field process...Extreme ultraviolet(EUV)observations are widely used in solar activity research and space weather forecasting since they can observe both the solar eruptions and the source regions of the solar wind.Flat field processing is indispensable to remove the instrumental non-uniformity of a solar EUV imager in producing high-quality scientific data from original observed data.FengYun-3E(FY-3E)is a meteorological satellite operated in a Sunsynchronous orbit,and the routine EUV imaging data from the Solar X-ray and Extreme Ultraviolet Imager(X-EUVI)onboard FY-3E has the characteristic of concentric rotation.Taking advantage of the concentric rotation,we propose a post-hoc flat field measurement method for its EUV 195A channel in this paper.This method removes the small-scale and time-varying component of coronal activities by taking the median value for each pixel along the time axis of a concentric rotation data cube,and then derives the large-scale and invariable component of the quiet coronal radiation,and finally generates a flat field image.The flat field can be generated with cadences from hundreds of minutes(one orbit)to several days.Higher flat field accuracy can be achieved by employing more data.Further analysis shows that our method is able to measure the instrumental spot-like nonuniformity possibly caused by contamination on the detector,which mostly disappears after the in-orbit selfcleaning process.It can also measure the quasi-periodic grid-like non-uniformity,possibly from the obscuration of the support mesh on the rear filter.After flat field correction,these instrumental non-uniformities from the original data are effectively removed.Moreover,the X-EUVI 195A data after dark and flat field corrections are consistent with the 193A imaging data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,verifying the suitability of the method.The post-hoc method does not occupy observation time,which is advantageous for space weather operations.Our method is not only suitable for FY-3E/X-EUVI but also a candidate method for the flat field measurement of future solar EUV telescopes.展开更多
New observations of auroras based on the wide-field aurora imager(WAI)onboard Fengyun-3D(FY-3D)satellite are exhibited in this paper.Validity of the WAI data is analyzed by comparing auroral boundaries derived from WA...New observations of auroras based on the wide-field aurora imager(WAI)onboard Fengyun-3D(FY-3D)satellite are exhibited in this paper.Validity of the WAI data is analyzed by comparing auroral boundaries derived from WAI observations with results obtained from data collected by the Special Sensor Ultraviolet Spectrographic Imager(SSUSI)aboard the Defense Meteorological Satellite Program(DMSP F18).Dynamic variations of the aurora with the solar wind,interplanetary magnetic field(IMF)parameters,and the SYM-H index are also investigated.The comparison of auroral boundaries indicates that the WAI data are morphologically valid and suitable to the study of auroral dynamics.Effective responses to solar wind parameters indicate that the WAI data can be useful to monitor and predict the Earth’s space weather.Since the configuration of aurora is a good indicator of the solar wind–magnetosphere–ionosphere(SW-M-I)coupling system,and can reflect the disturbance of the space environment,the WAI will provide important data to help us to study the physical processes in space.展开更多
The dual-wavelength extreme ultraviolet camera(EUC)for the Queqiao-2 relay satellite of the Chang’E-7(CE-7)mission operates at 30.4 and 83.4 nm independently to simultaneously image the plasmasphere,magnetosheath,and...The dual-wavelength extreme ultraviolet camera(EUC)for the Queqiao-2 relay satellite of the Chang’E-7(CE-7)mission operates at 30.4 and 83.4 nm independently to simultaneously image the plasmasphere,magnetosheath,and ionospheric outflow from a lunar orbit.Each channel of the EUC is consisted of a concave multilayer mirror and a photoncounting imaging detector.This simple system achieves a large field of view(FOV),high spatial resolution,and optimized photon transmission efficiency to capture high-quality images of very weak extreme ultraviolet emissions in Earth space.Here we present the detailed design,tests,and calibrations of the EUC.Ground geometrical tests showed that the FOV was 20.2°for the 30.4 nm channel and 20.3°for the 83.4 nm channel,and the spatial resolution was 0.09°for both channels.Geometric distortion was corrected to be less than 1%.Pixels can be further binned on the ground to achieve higher sensitivity.Radiometric calibration results demonstrate that the sensitivity is 0.103 counts s^(-1)Rayleigh^(-1)pixel^(-1)at 30.4 nm channel and 0.061 counts s^(-1)Rayleigh^(-1)pixel^(-1)at 83.4 nm channel,with a calibration accuracy of~12%.The exposure can be flexibly set between 1–1500 s,with a longer exposure time achievable through time-delay integration during ground processing.The performance of the EUC fulfills the requirements of the scientific targets for the CE-7 mission and could significantly contribute to investigations of the solar wind-magnetosphere-ionosphere coupling system.展开更多
The dual-wavelength extreme ultraviolet camera(EUC)onboard the Queqiao-2 relay satellite of the Chang'E-7(CE-7)mission will be used to investigate the global structure and dynamics of the Earth's magnetosheath...The dual-wavelength extreme ultraviolet camera(EUC)onboard the Queqiao-2 relay satellite of the Chang'E-7(CE-7)mission will be used to investigate the global structure and dynamics of the Earth's magnetosheath and plasmasphere by simultaneously capturing emissions at 30.4 and 83.4 nm.In geospace,there are two emission sources at 30.4 nm:resonantly scattered emissions from plasmaspheric He+ions and solar wind charge-exchange in the Earth's magnetosheath.The sources of 83.4 nm emission include the ionospheric outflow O+and the plasmaspheric O+ions,both of which resonantly scatter sunlight at this wavelength.Global images at these wavelengths will enhance understanding of mass and energy transportation in solar wind-magnetosphere-ionosphere couplings,crucial for comprehending space weather.The Moon is an ideal platform for global imaging,allowing the EUC's two optical heads operating at 30.4 and 83.4 nm,each with a circular field of view of 20°to capture spatial resolution of~0.1REfor the plasmasphere,~0.3R_(E)for the magnetosheath,and~0.3R_(E)for the ionospheric outflow in the meridian plane perpendicular to the Earth-Moon line.The sensitivities are as follows:0.1 counts s-1Rayleigh-1at 30.4 nm channel for an angular resolution of 0.1°and 0.07 counts s-1Rayleigh-1at 83.4 nm channel for an angular resolution of 0.3°.Sufficient sensitivity was achieved to obtain plasmaspheric images every 10 min,magnetosheath images every 10–20 min,and ionospheric outflow images every 10 min.All of the original photon signals are transmitted to the ground,allowing for flexible processing of spatial and temporal resolutions.展开更多
基金supported by the National Key R&D Program of China(2021YFA0718600)the National Natural Science Foundations of China(NSFC,Grant Nos.41931073,41774195)+2 种基金Ten-thousand Talents Program of JingSong Wang,and the Specialized Research Fund for State Key Laboratoriessupported by the Strategic Priority Research Program of the Chinese Academy of Sciences,Grant No.XDA 15018400supported by the China Postdoctoral Science Foundation(2021M700246)。
文摘Extreme ultraviolet(EUV)observations are widely used in solar activity research and space weather forecasting since they can observe both the solar eruptions and the source regions of the solar wind.Flat field processing is indispensable to remove the instrumental non-uniformity of a solar EUV imager in producing high-quality scientific data from original observed data.FengYun-3E(FY-3E)is a meteorological satellite operated in a Sunsynchronous orbit,and the routine EUV imaging data from the Solar X-ray and Extreme Ultraviolet Imager(X-EUVI)onboard FY-3E has the characteristic of concentric rotation.Taking advantage of the concentric rotation,we propose a post-hoc flat field measurement method for its EUV 195A channel in this paper.This method removes the small-scale and time-varying component of coronal activities by taking the median value for each pixel along the time axis of a concentric rotation data cube,and then derives the large-scale and invariable component of the quiet coronal radiation,and finally generates a flat field image.The flat field can be generated with cadences from hundreds of minutes(one orbit)to several days.Higher flat field accuracy can be achieved by employing more data.Further analysis shows that our method is able to measure the instrumental spot-like nonuniformity possibly caused by contamination on the detector,which mostly disappears after the in-orbit selfcleaning process.It can also measure the quasi-periodic grid-like non-uniformity,possibly from the obscuration of the support mesh on the rear filter.After flat field correction,these instrumental non-uniformities from the original data are effectively removed.Moreover,the X-EUVI 195A data after dark and flat field corrections are consistent with the 193A imaging data from the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory,verifying the suitability of the method.The post-hoc method does not occupy observation time,which is advantageous for space weather operations.Our method is not only suitable for FY-3E/X-EUVI but also a candidate method for the flat field measurement of future solar EUV telescopes.
基金the National Science Foundation of China(41327802,41774152 and 41674155)in part by Youth Innovation Promotion Association of the Chinese Academy of Sciences(2017258)the Strategic Priority Program on Space Science,Chinese Academy of Sciences,Grant No.XDA15350203。
文摘New observations of auroras based on the wide-field aurora imager(WAI)onboard Fengyun-3D(FY-3D)satellite are exhibited in this paper.Validity of the WAI data is analyzed by comparing auroral boundaries derived from WAI observations with results obtained from data collected by the Special Sensor Ultraviolet Spectrographic Imager(SSUSI)aboard the Defense Meteorological Satellite Program(DMSP F18).Dynamic variations of the aurora with the solar wind,interplanetary magnetic field(IMF)parameters,and the SYM-H index are also investigated.The comparison of auroral boundaries indicates that the WAI data are morphologically valid and suitable to the study of auroral dynamics.Effective responses to solar wind parameters indicate that the WAI data can be useful to monitor and predict the Earth’s space weather.Since the configuration of aurora is a good indicator of the solar wind–magnetosphere–ionosphere(SW-M-I)coupling system,and can reflect the disturbance of the space environment,the WAI will provide important data to help us to study the physical processes in space.
基金supported by the Chinese Lunar Exploration Projectsupported by the National Natural Science Foundation of China(Grant Nos.42222408&42441809)+1 种基金the National Key Research and Development Program of China(Grant No.2021YFA0718600)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y2021027)。
文摘The dual-wavelength extreme ultraviolet camera(EUC)for the Queqiao-2 relay satellite of the Chang’E-7(CE-7)mission operates at 30.4 and 83.4 nm independently to simultaneously image the plasmasphere,magnetosheath,and ionospheric outflow from a lunar orbit.Each channel of the EUC is consisted of a concave multilayer mirror and a photoncounting imaging detector.This simple system achieves a large field of view(FOV),high spatial resolution,and optimized photon transmission efficiency to capture high-quality images of very weak extreme ultraviolet emissions in Earth space.Here we present the detailed design,tests,and calibrations of the EUC.Ground geometrical tests showed that the FOV was 20.2°for the 30.4 nm channel and 20.3°for the 83.4 nm channel,and the spatial resolution was 0.09°for both channels.Geometric distortion was corrected to be less than 1%.Pixels can be further binned on the ground to achieve higher sensitivity.Radiometric calibration results demonstrate that the sensitivity is 0.103 counts s^(-1)Rayleigh^(-1)pixel^(-1)at 30.4 nm channel and 0.061 counts s^(-1)Rayleigh^(-1)pixel^(-1)at 83.4 nm channel,with a calibration accuracy of~12%.The exposure can be flexibly set between 1–1500 s,with a longer exposure time achievable through time-delay integration during ground processing.The performance of the EUC fulfills the requirements of the scientific targets for the CE-7 mission and could significantly contribute to investigations of the solar wind-magnetosphere-ionosphere coupling system.
基金supported by the National Natural Science Foundation of China(Grant Nos.42222408 and 41931073)the National Key Research and Development Program of China(Grant No.2021YFA0718600)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.Y2021027)。
文摘The dual-wavelength extreme ultraviolet camera(EUC)onboard the Queqiao-2 relay satellite of the Chang'E-7(CE-7)mission will be used to investigate the global structure and dynamics of the Earth's magnetosheath and plasmasphere by simultaneously capturing emissions at 30.4 and 83.4 nm.In geospace,there are two emission sources at 30.4 nm:resonantly scattered emissions from plasmaspheric He+ions and solar wind charge-exchange in the Earth's magnetosheath.The sources of 83.4 nm emission include the ionospheric outflow O+and the plasmaspheric O+ions,both of which resonantly scatter sunlight at this wavelength.Global images at these wavelengths will enhance understanding of mass and energy transportation in solar wind-magnetosphere-ionosphere couplings,crucial for comprehending space weather.The Moon is an ideal platform for global imaging,allowing the EUC's two optical heads operating at 30.4 and 83.4 nm,each with a circular field of view of 20°to capture spatial resolution of~0.1REfor the plasmasphere,~0.3R_(E)for the magnetosheath,and~0.3R_(E)for the ionospheric outflow in the meridian plane perpendicular to the Earth-Moon line.The sensitivities are as follows:0.1 counts s-1Rayleigh-1at 30.4 nm channel for an angular resolution of 0.1°and 0.07 counts s-1Rayleigh-1at 83.4 nm channel for an angular resolution of 0.3°.Sufficient sensitivity was achieved to obtain plasmaspheric images every 10 min,magnetosheath images every 10–20 min,and ionospheric outflow images every 10 min.All of the original photon signals are transmitted to the ground,allowing for flexible processing of spatial and temporal resolutions.
