The performance analysis and simulation of coding schemes based on the modeling Ka band fixed satellite channel have been presented. The results indicate that concatenated codes with large inner interleaving depth ha...The performance analysis and simulation of coding schemes based on the modeling Ka band fixed satellite channel have been presented. The results indicate that concatenated codes with large inner interleaving depth have good performance and high spectrum efficiency. The studies also show that simple block interleaving is very effective in combating the slow frequency nonselective fading of Ka band.展开更多
Aquarius is the second satellite mission to focus on the remote sensing of sea-surface salinity from space and it has mapped global sea-surface salinity for nearly 3 years since its launch in 2011. However,benefiting ...Aquarius is the second satellite mission to focus on the remote sensing of sea-surface salinity from space and it has mapped global sea-surface salinity for nearly 3 years since its launch in 2011. However,benefiting from the high atmospheric transparency and moderate sensitivity to wind speed of the L-band brightness temperature(TB),the Aquarius L-band radiometer can actually provide a new technique for the remote sensing of wind speed. In this article,the sea-surface wind speeds derived from TBs measured by Aquarius' L-band radiometer are presented,the algorithm for which is developed and validated using multisource wind speed data,including Wind Sat microwave radiometer and National Data Buoy Center buoy data,and the Hurricane Research Division of the Atlantic Oceanographic and Meteorological Laboratory wind field product. The error analysis indicates that the performance of retrieval algorithm is good. The RMSE of the Aquarius wind-speed algorithm is about 1 and 1.5 m/s for global oceans and areas of tropical hurricanes,respectively. Consequently,the applicability of using the Aquarius L-band radiometer as a near all-weather wind-speed measuring method is verified.展开更多
Using earth satellite observation means, remote sensing information distilled technique and regional research production, we have roundly analyzed and made an integrated evaluation about the Lop Nur nuclear test field...Using earth satellite observation means, remote sensing information distilled technique and regional research production, we have roundly analyzed and made an integrated evaluation about the Lop Nur nuclear test field in western China. This product reveals the rarely-known nuke explosion effect and response events of geology conditions. It also offers us legible and practical first-hand materials about human extreme effects, important engineering environment and intimidating influence process. By excavating and appraising the materials gradually on the natural environment factors changing in the test field through macroscopic elimination and typical filtration, it can supply basic scientific data for security of national nuclear usage, appraising the nuclear environment synthetically and developing nuclear strategy expediently.展开更多
The attractiveness of flying several SAR （synthetic aperture radar） satellites in a semi-active configuration has been proposed by several studies. The closest implementation of such a mission scenario is exemplifie...The attractiveness of flying several SAR （synthetic aperture radar） satellites in a semi-active configuration has been proposed by several studies. The closest implementation of such a mission scenario is exemplified by the current Terra SAR-X and Tandem-X mission, where both spacecraft are identical monostatic platforms capable of operating in various modes. The bistatic operation mode of the Tandem-X mission is a basic form of the semi-active multi-static operation mode where one satellite serves as a transmitter while the other records the scattered signals simultaneously. The use of a typical monostatic SAR spacecraft operating in-tandem with several receiver only spacecraft is a semi-active mode of operation. This paper examines the capabilities of implementing a constellation of S-band spaceborne SAR platform for alongtrack interferometry over the equatorial region for velocity measurement with particular focus on ship detection. The orbit for the mission is an inclined circular low Earth orbit, which ensures high revisit time, quick coverage and high data throughput. The pendulum configuration is adopted to maintain the relative distance between successive SAR platforms. The conditions and constraints necessary to achieve the orbit geometry required to conduct alongtrack interferometry are defined. The alongtrack separation between platforms necessary to measure specified ship velocity is also discussed. Finally an error budget estimate of the measure radial velocity is provided.展开更多
Atmospheric SO_2 has a significant impact on the urban environment and global climate. Band Residual Difference Algorithm(BRD) and Differential Optical Absorption Spectroscopy(DOAS) were used respectively by NASA and ...Atmospheric SO_2 has a significant impact on the urban environment and global climate. Band Residual Difference Algorithm(BRD) and Differential Optical Absorption Spectroscopy(DOAS) were used respectively by NASA and ESA science team to derive SO_2 columns from satellite observations, but there are few studies on the comparison and validation of BRD and DOAS SO_2 retrievals under the same observation conditions. In this study, the radiative transfer model SCIATRAN was firstly used to validate the accuracies of BRD and DOAS SO_2 retrievals, and analyse the uncertainty of SO_2 retrieval caused by band selection,O_3 absorption, aerosol, surface reflectance, solar and viewing zenith angle. Finally, BRD and DOAS algorithms were applied to the same radiances from satellite observations, and comparisons of BRD and DOAS SO_2 retrievals were conducted over volcanic eruption and North China. Results show that, for the case with low SO_2 columns, BRD SO_2 retrievals have higher retrieval accuracy than DOAS, but typical seasonal variation with high SO_2 column in winter and low in summer can be more clearly discernible in DOAS SO_2 retrievals than BRD from satellite observations. For the case with high SO_2 columns, the differences between BRD(310.8–314.4 nm) and DOAS(315–327 nm) retrievals are large, and the value and accuracy of BRD(310.8–314.4 nm) SO_2 retrievals are lower than those of DOAS(315–327 nm) retrievals. Compared with the SO_2 inputs in forward model, both BRD(310.8–314.4 nm) and DOAS(315–327 nm) SO_2 retrievals are underestimated for the case with high SO_2 columns. The selection of wavelength range can significantly affect the accuracy of SO_2 retrieval. The error of BRD SO_2 retrieval from 310.8–314.4 nm is lower than other bands in the ultraviolet spectral region(306–327 nm). The increase of wavelength in the ultraviolet spectral region306–330 nm can reduce the underestimation of DOAS SO_2 retrievals in the case of high SO_2 column, but slight overestimation of SO_2 retrieval is found from the 315–327 nm range in the case of low SO_2 column. The values of BRD and DOAS SO_2 retrieval decrease with atmospheric O_3 column and aerosol optical depth increasing, but increase with surface reflectance increasing. Large solar zenith angle and viewing zenith angle can introduce more errors to the BRD and DOAS SO_2 retrievals. This study is important for the improvement of retrieval algorithm and the application of SO_2 products from satellite observations.展开更多
文摘The performance analysis and simulation of coding schemes based on the modeling Ka band fixed satellite channel have been presented. The results indicate that concatenated codes with large inner interleaving depth have good performance and high spectrum efficiency. The studies also show that simple block interleaving is very effective in combating the slow frequency nonselective fading of Ka band.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA09A505)the National Natural Science Foundation for Young Scientists of China(No.41306183)
文摘Aquarius is the second satellite mission to focus on the remote sensing of sea-surface salinity from space and it has mapped global sea-surface salinity for nearly 3 years since its launch in 2011. However,benefiting from the high atmospheric transparency and moderate sensitivity to wind speed of the L-band brightness temperature(TB),the Aquarius L-band radiometer can actually provide a new technique for the remote sensing of wind speed. In this article,the sea-surface wind speeds derived from TBs measured by Aquarius' L-band radiometer are presented,the algorithm for which is developed and validated using multisource wind speed data,including Wind Sat microwave radiometer and National Data Buoy Center buoy data,and the Hurricane Research Division of the Atlantic Oceanographic and Meteorological Laboratory wind field product. The error analysis indicates that the performance of retrieval algorithm is good. The RMSE of the Aquarius wind-speed algorithm is about 1 and 1.5 m/s for global oceans and areas of tropical hurricanes,respectively. Consequently,the applicability of using the Aquarius L-band radiometer as a near all-weather wind-speed measuring method is verified.
基金The State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chi-nese Academy of Sciences, the open fund item (No. SKLLQG0701) to subsidizedthe constructprogram of the key discipline in Hunan Province, China, the fund item (No. D2007001) the State Key Labo-ratories of Continental Dynamics,Northwest University, the open fund item (No. DL2006001) to combine subsi-dized.
文摘Using earth satellite observation means, remote sensing information distilled technique and regional research production, we have roundly analyzed and made an integrated evaluation about the Lop Nur nuclear test field in western China. This product reveals the rarely-known nuke explosion effect and response events of geology conditions. It also offers us legible and practical first-hand materials about human extreme effects, important engineering environment and intimidating influence process. By excavating and appraising the materials gradually on the natural environment factors changing in the test field through macroscopic elimination and typical filtration, it can supply basic scientific data for security of national nuclear usage, appraising the nuclear environment synthetically and developing nuclear strategy expediently.
文摘The attractiveness of flying several SAR （synthetic aperture radar） satellites in a semi-active configuration has been proposed by several studies. The closest implementation of such a mission scenario is exemplified by the current Terra SAR-X and Tandem-X mission, where both spacecraft are identical monostatic platforms capable of operating in various modes. The bistatic operation mode of the Tandem-X mission is a basic form of the semi-active multi-static operation mode where one satellite serves as a transmitter while the other records the scattered signals simultaneously. The use of a typical monostatic SAR spacecraft operating in-tandem with several receiver only spacecraft is a semi-active mode of operation. This paper examines the capabilities of implementing a constellation of S-band spaceborne SAR platform for alongtrack interferometry over the equatorial region for velocity measurement with particular focus on ship detection. The orbit for the mission is an inclined circular low Earth orbit, which ensures high revisit time, quick coverage and high data throughput. The pendulum configuration is adopted to maintain the relative distance between successive SAR platforms. The conditions and constraints necessary to achieve the orbit geometry required to conduct alongtrack interferometry are defined. The alongtrack separation between platforms necessary to measure specified ship velocity is also discussed. Finally an error budget estimate of the measure radial velocity is provided.
基金supported by the National Natural Science Foundation of China (Grant No. 41501413)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology (Grant No. 05-Y20A16-9001-15/17)the Partnership with chiNa on space Data (PANDA) (Grant No. 606719)
文摘Atmospheric SO_2 has a significant impact on the urban environment and global climate. Band Residual Difference Algorithm(BRD) and Differential Optical Absorption Spectroscopy(DOAS) were used respectively by NASA and ESA science team to derive SO_2 columns from satellite observations, but there are few studies on the comparison and validation of BRD and DOAS SO_2 retrievals under the same observation conditions. In this study, the radiative transfer model SCIATRAN was firstly used to validate the accuracies of BRD and DOAS SO_2 retrievals, and analyse the uncertainty of SO_2 retrieval caused by band selection,O_3 absorption, aerosol, surface reflectance, solar and viewing zenith angle. Finally, BRD and DOAS algorithms were applied to the same radiances from satellite observations, and comparisons of BRD and DOAS SO_2 retrievals were conducted over volcanic eruption and North China. Results show that, for the case with low SO_2 columns, BRD SO_2 retrievals have higher retrieval accuracy than DOAS, but typical seasonal variation with high SO_2 column in winter and low in summer can be more clearly discernible in DOAS SO_2 retrievals than BRD from satellite observations. For the case with high SO_2 columns, the differences between BRD(310.8–314.4 nm) and DOAS(315–327 nm) retrievals are large, and the value and accuracy of BRD(310.8–314.4 nm) SO_2 retrievals are lower than those of DOAS(315–327 nm) retrievals. Compared with the SO_2 inputs in forward model, both BRD(310.8–314.4 nm) and DOAS(315–327 nm) SO_2 retrievals are underestimated for the case with high SO_2 columns. The selection of wavelength range can significantly affect the accuracy of SO_2 retrieval. The error of BRD SO_2 retrieval from 310.8–314.4 nm is lower than other bands in the ultraviolet spectral region(306–327 nm). The increase of wavelength in the ultraviolet spectral region306–330 nm can reduce the underestimation of DOAS SO_2 retrievals in the case of high SO_2 column, but slight overestimation of SO_2 retrieval is found from the 315–327 nm range in the case of low SO_2 column. The values of BRD and DOAS SO_2 retrieval decrease with atmospheric O_3 column and aerosol optical depth increasing, but increase with surface reflectance increasing. Large solar zenith angle and viewing zenith angle can introduce more errors to the BRD and DOAS SO_2 retrievals. This study is important for the improvement of retrieval algorithm and the application of SO_2 products from satellite observations.
