TJ95 2000063876激光反卫星技术的发展现状=Status of laser antisatellitetechnique[刊,中]/付伟(电子工业部第53研究所.辽宁,锦州(121000))//光电对抗与无源干扰.—1999,(2).—13—18为了有效对抗军事卫星,先进国家已经开展了反卫星...TJ95 2000063876激光反卫星技术的发展现状=Status of laser antisatellitetechnique[刊,中]/付伟(电子工业部第53研究所.辽宁,锦州(121000))//光电对抗与无源干扰.—1999,(2).—13—18为了有效对抗军事卫星,先进国家已经开展了反卫星激光武器的研制,并具备初步的反卫星能力。该文对该项技术的发展作了综述介绍。(方舟)展开更多
Knowledge of the vertical distribution of aerosols in the free troposphere is important for estimating their impact on climate. In this study, direct observations of the vertical distribution of aerosols in the free t...Knowledge of the vertical distribution of aerosols in the free troposphere is important for estimating their impact on climate. In this study, direct observations of the vertical distribution of aerosols in the free troposphere are made using surface Micro-Pulse Lidar (MPL) measurements. The MPL measurements were made at the Loess Plateau (35.95°N, 104.1°E), which is near the major dust source regions of the Taklimakan and Gobi deserts. The vertical distribution of the MPL backscattering suggested that nondust aerosols floated from ground level to an altitude of approximately 9 km around the source regions. Early morning hours are characterized by a shallow aerosol layer of a few hundred meters thick. As the day progresses, strong convective eddies transport the aero- sols vertically to more than 1500 m.展开更多
Airborne light detection and ranging( LIDAR) has revolutionized conventional methods for digital terrain models( DTMs) acquisition. Ground filtering for airborne LIDAR is one of the core steps taken to obtain a high q...Airborne light detection and ranging( LIDAR) has revolutionized conventional methods for digital terrain models( DTMs) acquisition. Ground filtering for airborne LIDAR is one of the core steps taken to obtain a high quality DTM. This paper presents a segments-based progressive TIN( triangulated irregular network) densification( SPTD) filter that can automatically separate ground points from non-ground points. The SPTD method is composed of two key steps: point cloud segmentation and clustering by iterative judgement. The clustering method uses the dual distance to obtain a set of seed points as a coarse spatial clustering process. Then the rest of the valid point clouds are classified iteratively. Finally,the datasets provided by ISPRS are utilized to test the filtering performance.In comparison with the commercial software Terra Solid,the experimental results show that the SPTD method in this paper can avoid single threshold restrictions. The expected accuracy of ground point determination is capable of producing reliable DTMs in the discontinuous areas.展开更多
During the total solar eclipse on July 22, 2009 in Wuhan, the joint observation test of Na layer and ionosphere was conducted by using the daytime observation atmospheric lidar and the GPS ionosphere detector. The res...During the total solar eclipse on July 22, 2009 in Wuhan, the joint observation test of Na layer and ionosphere was conducted by using the daytime observation atmospheric lidar and the GPS ionosphere detector. The results show that the full width at half maximum(FWHM) of Na layer density slightly narrowed during the total solar eclipse and broadened after the eclipse, while the height of Na peak slightly decreased in the eclipse and increased after the eclipse. These implying that Na layer changes reflect the rapid process of sunrise and sunset. The ionosphere total electron content(TEC) and the sky background light noise also presented an obvious fluctuation characteristic with the changes of solar irradiation during the process of total solar eclipse. The difference lies in that the changes of FWHM of Na layer atoms are much slower than that of ionosphere, the reason for this might be that the Na layer, after being disturbed by the total solar eclipse, will generate a series of complicated photochemical reactions and momentum transport processes, and then recombine the Na atoms. The Na atoms to be detected by the lidar need a lag process, which rightly conforms to the theoretical simulated results.展开更多
In view of the problem of false alarm in imaging space-based laser warning system, the effects of sunlight and lightning on the threaten laser detection and attack event determination are studied by analyzing and calc...In view of the problem of false alarm in imaging space-based laser warning system, the effects of sunlight and lightning on the threaten laser detection and attack event determination are studied by analyzing and calculating the radiant energy density and space-time feature of imaging spot, respectively. The results show that the main false alarm resourses of space- based laser warning system are sunlight and lightning. The sunlight should exposure the detector directly in one ninth of the satfllite orbital period, and the imaging spot of sun is similar to the attack laser. The lightning imaging spot is similar to the illumination laser. About 1.4 lightning events can occur in the field of view （FOV） of the warning system per second. It could not discriminate spots of sun, lightning and threaten laser by the frame subtraction technology.展开更多
文摘TJ95 2000063876激光反卫星技术的发展现状=Status of laser antisatellitetechnique[刊,中]/付伟(电子工业部第53研究所.辽宁,锦州(121000))//光电对抗与无源干扰.—1999,(2).—13—18为了有效对抗军事卫星,先进国家已经开展了反卫星激光武器的研制,并具备初步的反卫星能力。该文对该项技术的发展作了综述介绍。(方舟)
基金supported by the National Natural Science Foundation of China under Grant Nos. 40628005 and 40633017
文摘Knowledge of the vertical distribution of aerosols in the free troposphere is important for estimating their impact on climate. In this study, direct observations of the vertical distribution of aerosols in the free troposphere are made using surface Micro-Pulse Lidar (MPL) measurements. The MPL measurements were made at the Loess Plateau (35.95°N, 104.1°E), which is near the major dust source regions of the Taklimakan and Gobi deserts. The vertical distribution of the MPL backscattering suggested that nondust aerosols floated from ground level to an altitude of approximately 9 km around the source regions. Early morning hours are characterized by a shallow aerosol layer of a few hundred meters thick. As the day progresses, strong convective eddies transport the aero- sols vertically to more than 1500 m.
基金Supported by the National Natural Science Foundation of China(No.41174002)the Opening Fund of Key Laboratory of the Ministry of Water Resources(No.2015003)the Fundamental Research Funds for the Central Universities(No.2014B38614)
文摘Airborne light detection and ranging( LIDAR) has revolutionized conventional methods for digital terrain models( DTMs) acquisition. Ground filtering for airborne LIDAR is one of the core steps taken to obtain a high quality DTM. This paper presents a segments-based progressive TIN( triangulated irregular network) densification( SPTD) filter that can automatically separate ground points from non-ground points. The SPTD method is composed of two key steps: point cloud segmentation and clustering by iterative judgement. The clustering method uses the dual distance to obtain a set of seed points as a coarse spatial clustering process. Then the rest of the valid point clouds are classified iteratively. Finally,the datasets provided by ISPRS are utilized to test the filtering performance.In comparison with the commercial software Terra Solid,the experimental results show that the SPTD method in this paper can avoid single threshold restrictions. The expected accuracy of ground point determination is capable of producing reliable DTMs in the discontinuous areas.
基金supported by the National Natural Science Foundation of China(Grant Nos.1097800341104101+1 种基金41101334)the National High-tech R&D Program
文摘During the total solar eclipse on July 22, 2009 in Wuhan, the joint observation test of Na layer and ionosphere was conducted by using the daytime observation atmospheric lidar and the GPS ionosphere detector. The results show that the full width at half maximum(FWHM) of Na layer density slightly narrowed during the total solar eclipse and broadened after the eclipse, while the height of Na peak slightly decreased in the eclipse and increased after the eclipse. These implying that Na layer changes reflect the rapid process of sunrise and sunset. The ionosphere total electron content(TEC) and the sky background light noise also presented an obvious fluctuation characteristic with the changes of solar irradiation during the process of total solar eclipse. The difference lies in that the changes of FWHM of Na layer atoms are much slower than that of ionosphere, the reason for this might be that the Na layer, after being disturbed by the total solar eclipse, will generate a series of complicated photochemical reactions and momentum transport processes, and then recombine the Na atoms. The Na atoms to be detected by the lidar need a lag process, which rightly conforms to the theoretical simulated results.
文摘In view of the problem of false alarm in imaging space-based laser warning system, the effects of sunlight and lightning on the threaten laser detection and attack event determination are studied by analyzing and calculating the radiant energy density and space-time feature of imaging spot, respectively. The results show that the main false alarm resourses of space- based laser warning system are sunlight and lightning. The sunlight should exposure the detector directly in one ninth of the satfllite orbital period, and the imaging spot of sun is similar to the attack laser. The lightning imaging spot is similar to the illumination laser. About 1.4 lightning events can occur in the field of view （FOV） of the warning system per second. It could not discriminate spots of sun, lightning and threaten laser by the frame subtraction technology.
