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Orthogonal waveform design with fractional programming on the ambiguity suppression of SAR systems

Science China(Information Sciences) 2024年第9期67卷 263-279页

作者： Yunkai DENG Yongwei ZHANG Zhimin ZHANG Wei WANG Heng ZHANG Department of space Microwave remote sensing System Aerospace Information Research InstituteChinese Academy of Sciences

Waveform diversity(WD) represents a dynamic and transformative technology widely used in radar systems to enhance sensitivity and discrimination capabilities. Recently, WD techniques have been extensively explored for their potential ambiguity suppression within synthetic aperture radar(SAR) *** these, the alternate transmitting mode combined with orthogonal waveforms emerges as a particularly promising solution. This study focuses on optimizing the power spectrum density(PSD) of signals to design and generate an orthogonal waveform pair that achieves both a low cross-correlation-to-autocorrelation ratio(CAR) and satisfactory imaging performance. Initially, we construct a fractional programming model with convex constraints to minimize the CAR. To address this challenge, we introduce an iterative optimization procedure for the PSD variable, which sequentially reduces the CAR. Each optimization step can be efficiently solved using a quadratically constrained quadratic program, ensuring that the resulting computational complexity remains low. Building on the optimized PSD, we established a parametric piecewise linear model to generate an orthogonal waveform pair. This model not only maintains a low CAR but achieves satisfactory imaging performance in real-time applications. Consequently, this orthogonal waveform pair effectively suppresses range ambiguity in SAR systems. Finally, we demonstrated the practicability and effectiveness of the proposed orthogonal waveforms through detailed simulation experiments, specifically targeting ambiguity suppression in conventional quad-polarization SAR systems.

关键词： synthetic aperture radar (SAR) waveform diversity (WD) ambiguity suppression orthogonal waveform fractional programming power spectrum density (PSD)

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Performance validation of High Mountain Asia 8-meter Digital Elevation Model using ICESat-2 geolocated photons

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Journal of Mountain Science 2024年第8期21卷 2562-2578页

作者： Giribabu DANDABATHULA Subham ROY Omkar Shashikant GHATAGE Vaibhav Balaso KOLASE Shwetambari SATPUTE Koushik GHOSH Sahibnoor KAUR Satyanarayana PONDARI Apurba Kumar BERA Sushil Kumar SRIVASTAV Regional remote sensing Centre-West National Remote Sensing CentreIndian Space Research OrganisationJodhpur 342005India Department of Geography School of Earth SciencesBharathidasan UniversityTiruchirappalli 620024India Centre for Climate Change and Water research Suresh Gyan Vihar UniversityJaipur 302017India Department of Geography Panjab UniversityChandigarh 160014India National remote sensing Centre Indian Space Research OrganisationHyderabad 500037India Regional Centres National Remote Sensing CentreIndian Space Research OrganisationNew Delhi 110049India

High Mountain Asia(HMA),recognized as a third pole,needs regular and intense studies as it is susceptible to climate *** accurate and high-resolution Digital Elevation Model(DEM)for this region enables us to analyze it in a 3D environment and understand its intricate role as the Water Tower of *** science teams of NASA realized an 8-m DEM using satellite stereo imagery for HMA,termed HMA 8-m *** this research,we assessed the vertical accuracy of HMA 8-m DEM using reference elevations from ICESat-2 geolocated photons at three test sites of varied topography and land *** were made from statistical quantifiers and elevation *** the world’s highest mountain,Mount Everest,and its surroundings,Root Mean Squared Error(RMSE)and Mean Absolute Error(MAE)resulted in 1.94 m and 1.66 m,respectively;however,a uniform positive bias observed in the elevation profiles indicates the seasonal snow cover change will dent the accurate estimation of the elevation in this sort of test *** second test site containing gentle slopes with forest patches has exhibited the Digital Surface Model(DSM)features with RMSE and MAE of 0.58 m and 0.52 m,*** third test site,situated in the Zanda County of the Qinghai-Tibet,is a relatively flat terrain bed,mostly bare earth with sudden river cuts,and has minimal errors with RMSE and MAE of 0.32 m and 0.29 m,respectively,and with a negligible ***,in one more test site,the feasibility of detecting the glacial lakes was tested,which resulted in exhibiting a flat surface over the surface of the lakes,indicating the potential of HMA 8-m DEM for deriving the hydrological *** results accrued in this investigation confirm that the HMA 8-m DEM has the best vertical accuracy and should be of high use for analyzing natural hazards and monitoring glacier surfaces.

关键词： High Mountain Asia Digital Elevation Model ICESat-2 geolocated photons Accuracy assessment

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Advances in Deep-Learning-based Precipitation Nowcasting Techniques

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Journal of Tropical Meteorology 2024年第3期30卷 337-350页

作者： ZHENG Qun LIU Qi LAO Ping LU Zhen-ci School of Earth and space Sciences/CMA-USTC Laboratory of Fengyun remote sensing University of Science and Technology of ChinaHefei 230026 China

Precipitation nowcasting,as a crucial component of weather forecasting,focuses on predicting very short-range precipitation,typically within six *** approach relies heavily on real-time observations rather than numerical weather *** core concept involves the spatio-temporal extrapolation of current precipitation fields derived from ground radar echoes and/or satellite images,which was generally actualized by employing computer image or vision ***,with stirring breakthroughs in artificial intelligence(AI)techniques,deep learning(DL)methods have been used as the basis for developing novel approaches to precipitation *** progress has been obtained in recent years,manifesting the strong potential of DL-based nowcasting models for their advantages in both prediction accuracy and computational *** paper provides an overview of these precipitation nowcasting approaches,from which two stages along the advancing in this field *** models that were established on an elementary neural network dominated in the first stage,while large meteorological models that were based on complex network architectures prevailed in the *** particular,the nowcasting accuracy of such data-driven models has been greatly increased by imposing suitable physical *** integration of AI models and physical models seems to be a promising way to improve precipitation nowcasting techniques further.

关键词： precipitation nowcasting deep learning neural network classic model large model

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Super-resolution Imaging of Telescopic Systems based on Optical-neural Network Joint Optimization

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research in Astronomy and Astrophysics 2024年第9期24卷 167-177页

作者： You-Hong Sun Tao Zhang Hao-Dong Shi Qiang Fu Jia-Nan Liu Kai-Kai Wang Chao Wang research Institute of Chongqing Changchun University of Science and TechnologyChangchun 130022China National and Local Joint Engineering research Center for space Photoelectric Technology Changchun University of Science and TechnologyChangchun 130022China The Institute of remote sensing Satellites China Academy of Space Technology(CAST)Beijing 100094China

Optical telescopes are an important tool for acquiring optical information about distant objects,and resolution is an important indicator that measures the ability to observe object ***,due to the effects of system aberration,atmospheric seeing,and other factors,the observed image of ground-based telescopes is often degraded,resulting in reduced *** paper proposes an optical-neural network joint optimization method to improve the resolution of the observed image by co-optimizing the point-spread function(PSF)of the telescopic system and the image super-resolution(SR)*** improve the speed of image reconstruction,we designed a generative adversarial net(LCR-GAN)with light parameters,which is much faster than the latest unsupervised *** reconstruct the PSF trained by the network in the optical path,a phase mask is *** improves the image reconstruction effect of LCR-GAN by reconstructing the PSF that best matches the *** results of simulation and verification experiments show that compared with the pure deep learning method,the SR image reconstructed by this method is rich in detail and it is easier to distinguish stars or stripes.

关键词： Techniques:image processing Telescopes Stars:imaging

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Urban growth scenario projection using heuristic cellular automata in arid areas considering the drought impact

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Journal of Arid Land 2024年第4期16卷 580-601页

作者： TANG Xiaoyan FENG Yongjiu LEI Zhenkun CHEN Shurui WANG Jiafeng WANG Rong TANG Panli WANG Mian JIN Yanmin TONG Xiaohua College of Surveying&Geo-Informatics Tongji UniversityShanghai 200092China Shanghai Key Laboratory of space Mapping and remote sensing for Planetary Exploration Tongji UniversityShanghai 200092China

Arid areas with low precipitation and sparse vegetation typically yield compact urban pattern,and drought directly impacts urban site selection,growth processes,and future *** simulation and projection based on cellular automata(CA)models is important to achieve sustainable urban development in arid *** developed a new CA model using bat algorithm(BA)named bat algorithm-probability-of-occurrence-cellular automata(BA-POO-CA)model by considering drought constraint to accurately delineate urban growth patterns and project future scenarios of Urumqi City and its surrounding areas,located in Xinjiang Uygur Autonomous Region,*** calibrated the BA-POO-CA model for the drought-prone study area with 2000 and 2010 data and validated the model with 2010 and 2020 data,and finally projected its urban scenarios in *** results showed that BA-POO-CA model yielded overall accuracy of 97.70%and figure-of-merits(FOMs)of 35.50%in 2010,and 97.70%and 26.70%in 2020,*** inclusion of drought intensity factor improved the performance of BA-POO-CA model in terms of FOMs,with increases of 5.50%in 2010 and 7.90%in 2020 than the model excluding drought intensity *** suggested that the urban growth of Urumqi City was affected by drought,and therefore taking drought intensity factor into account would contribute to simulation *** BA-POO-CA model including drought intensity factor was used to project two possible scenarios(i.e.,business-as-usual(BAU)scenario and ecological scenario)in *** the BAU scenario,the urban growth dominated mainly in urban fringe areas,especially in the northern part of Toutunhe District,Xinshi District,and Midong *** exceptional and extreme drought areas as a spatial constraint,the urban growth was mainly concentrated in the"main urban areas-Changji-Hutubi"corridor urban pattern in the ecological *** results of this research can help to adjust urban planning and development *** mode

关键词： bat algorithm cellular automata(CA) probability-of-occurrence drought intensity algorithm-probability-of-occurrence-cellular automata(BA-POO-CA)model arid areas

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An improved wind quality control for the China-France Oceanography Satellite (CFOSAT) scatterometer

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Acta Oceanologica Sinica 2024年第5期43卷 100-109页

作者： Xiaoheng Mou Wenming Lin School of Marine Sciences Nanjing University of Information Science and TechnologyNanjing 210044China Key Laboratory of space Ocean remote sensing and Application Ministry of Natural ResourcesBeijing 100081China

Quality control(QC)is an essential procedure in scatterometer wind retrieval,which is used to distinguish good-quality data from poor-quality wind vector cells(WVCs)for the sake of wind *** current wind processor of the China-France Oceanography Satellite(CFOSAT)scatterometer(CSCAT)adopts a maximum likelihood estimator(MLE)-based QC method to filter WVCs affected by geophysical noise,such as rainfall and wind *** the first Ku-band rotating fan-beam scatterometer,CSCAT can acquire up to 16 observations over a single WVC,giving abundant information with diverse incidence/azimuth angles,as such its MLE statistical characteristics may be different from the previous *** this study,several QC indicators,including MLE,its spatially averaged value(MLE_(m)),and the singularity exponents(SE),are analyzed using the collocated Global Precipitation Mission rainfall data as well as buoy data,to compare their sensitivity to rainfall and wind *** results show that wind error characteristics of CSCAT under different QC methods are similar to those of other Ku-band scatterometers,i.e.,SE is more suitable than other parameters for the wind QC at outer-swath and nadir regions,while MLE_(m) is the best QC indicator for the sweet region ***,SE is much more favorable than others at high wind *** combining different indicators,an improved QC method is developed for *** validation with the collocated buoy data shows that it accepts more WVCs,and in turn,improves the quality control of CSCAT wind data.

关键词： China-France Oceanography Satellite(CFOSAT) scatterometer winds quality control(QC) singularity exponent(SE)

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A review on the developments and space applications of mid- and long-wavelength infrared detection technologies

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Frontiers of Information Technology & Electronic Engineering 2024年第8期25卷 1031-1056页

作者： Yuying WANG Jindong LI Hezhi SUN Xiang LI Beijing Institute of spacecraft System Engineering China Academy of Space TechnologyBejing 100094China Institute of remote sensing Satellite China Academy of Space TechnologyBeijing 100094China

Mid-wavelength infrared(MWIR)detection and long-wavelength infrared(LWIR)detection constitute the key technologies for space-based Earth observation and astronomical *** advanced ability of infrared(IR)detection technology to penetrate the atmosphere and identify the camouflaged targets makes it excellent for space-based remote ***,such detectors play an essential role in detecting and tracking low-temperature and far-distance moving ***,due to the diverse scenarios in which space-based IR detection systems are built,the key parameters of IR technologies are subject to unique *** review the developments and features of MWIR and LWIR detectors with a particular focus on their applications in space-based *** conduct a comprehensive analysis of key performance indicators for IR detection systems,including the ground sampling distance(GSD),operation range,and noise equivalent temperature difference(NETD)among others,and their interconnections with IR detector ***,the influences of pixel distance,focal plane array size,and operation temperature of space-based IR remote sensing are *** development requirements and technical challenges of MWIR and LWIR detection systems are also identified to achieve high-quality space-based observation platforms.

关键词： Infrared detection space application Mid-and long-wavelength infrared detection space-based Earth observation remote sensing

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A New Algorithm of Rain Type Classification for GPM Dual-Frequency Precipitation Radar in Summer Tibetan Plateau

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Advances in Atmospheric Sciences 2024年第11期41卷 2093-2111页

作者： Yunfei FU Liu YANG Zhenhao WU Peng ZHANG Songyan GU Lin CHEN Sun NAN School of Earth and space Sciences CMA-USTC Laboratory of Fengyun Remote SensingUniversity of Science and Technology of ChinaHefei 230026China Hubei Key Laboratory for Heavy Rain Monitoring and Warning research Institute of Heavy RainChina Meteorological AdministrationWuhan 430205China National Satellite Meteorological Center China Meteorological AdministrationBeijing 100081China

In this study, a new rain type classification algorithm for the Dual-Frequency Precipitation Radar(DPR) suitable over the Tibetan Plateau(TP) was proposed by analyzing Global Precipitation Measurement(GPM) DPR Level-2 data in summer from 2014 to 2020. It was found that the DPR rain type classification algorithm(simply called DPR algorithm) has mis-identification problems in two aspects in summer TP. In the new algorithm of rain type classification in summer TP,four rain types are classified by using new thresholds, such as the maximum reflectivity factor, the difference between the maximum reflectivity factor and the background maximum reflectivity factor, and the echo top height. In the threshold of the maximum reflectivity factors, 30 d BZ and 18 d BZ are both thresholds to separate strong convective precipitation, weak convective precipitation and weak precipitation. The results illustrate obvious differences of radar reflectivity factor and vertical velocity among the three rain types in summer TP, such as the reflectivity factor of most strong convective precipitation distributes from 15 d BZ to near 35 d BZ from 4 km to 13 km, and increases almost linearly with the decrease in height. For most weak convective precipitation, the reflectivity factor distributes from 15 d BZ to 28 d BZ with the height from 4 km to 9 km. For weak precipitation, the reflectivity factor mainly distributes in range of 15–25 d BZ with height within 4–10 km. It is also shows that weak precipitation is the dominant rain type in summer TP, accounting for 40%–80%,followed by weak convective precipitation(25%–40%), and strong convective precipitation has the least proportion(less than 30%).

关键词： satellite precipitation radar rain type classification method Tibetan Plateau strong convective precipitation

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An empirical method for joint inversion of wave and wind parameters based on SAR and wave spectrometer data

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Acta Oceanologica Sinica 2024年第5期43卷 133-144页

作者： Yong Wan Xiaona Zhang Shuyan Lang Ennan Ma Yongshou Dai College of Oceanography and space Informatics China University of PetroleumQingdao 266580China National Satellite Marine Application Center Beijing 100081China Key Laboratory of space Ocean remote sensing and Application Ministry of Natural ResourcesBeijing 100081China College of Control Science and Engineering China University of PetroleumQingdao 266580China

Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave ***,they face inherent limitations in observing sea surface *** systems,for instance,are hindered by an azimuth cut-off phenomenon in sea surface wind field *** spectrometers,while unaffected by the azimuth cutoff phenomenon,struggle with low azimuth resolution,impacting the capture of detailed wave and wind field *** study utilizes SAR and surface wave investigation and monitoring(SWIM)data to initially extract key feature parameters,which are then prioritized using the extreme gradient boosting(XGBoost)*** research further addresses feature collinearity through a combined analysis of feature importance and correlation,leading to the development of an inversion model for wave and wind parameters based on XGBoost.A comparative analysis of this model with ERA5 reanalysis and buoy data for of significant wave height,mean wave period,wind direction,and wind speed reveals root mean square errors of 0.212 m,0.525 s,27.446°,and 1.092 m/s,compared to 0.314 m,0.888 s,27.698°,and 1.315 m/s from buoy data,*** results demonstrate the model’s effective retrieval of wave and wind ***,the model,incorporating altimeter and scatterometer data,is evaluated against SAR/SWIM single and dual payload inversion methods across different wind *** comparison highlights the model’s superior inversion accuracy over other methods.

关键词： synthetic aperture radar(SAR) wave spectrometer extreme gradient boosting(XGBoost) joint inversion method wave and wind parameters

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Quantized Redshift and its Significance for Recent Observation

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research in Astronomy and Astrophysics 2024年第9期24卷 156-166页

作者： Arindam Mal Sarbani Palit Christopher C.Fulton Sisir Roy Indian space research organization Space Applications CentreAhmedabadIndia Indian Statistical Institute CVPR UnitKolkataIndia Protostar Inc.15652 Carrousel DriveCanyon CountryCA 91387USA National Institute of Advanced Studies IISC CampusBangaloreIndia

With the recent observational evidence in extragalactic astronomy,the interpretation of the nature of quasar redshift continues to be a research *** high redshifts are being detected for extragalactic objects that are presumably very distant and young while also exhibiting properties that are characteristic of a more mature galaxy such as *** to Halton Arp and Geoffrey Burbidge,redshift disparities consist of an intrinsic component and are related to an evolutionary *** observed redshift periodicity at integer multiples of0.089 in log scale and Burbidge observed redshift periodicity at integer multiples of 0.061 in linear *** Singular Value Decomposition based periodicity estimation is known to be superior for noisy data sets,especially when the data contain multiple harmonics and overtones,mainly irregular in nature,we have chosen it to be our primary tool for analysis of the quasar-galaxy pair redshift *** have observed a fundamental periodicity of0.051 with a confidence interval of 95%in linear scale with the site-available Sloan Digital Sky Survey Data Release 7(SDSS DR7)quasar-galaxy pair data *** have independently generated quasar-galaxy pair data sets from both 2d F and SDSS and found fundamental periodicities of 0.077 and 0.089,respectively,in log scale with a confidence interval of 95%.

关键词： galaxies:distances and redshifts (galaxies:)quasars:absorption lines cosmology:observations

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