In the past few decades, applications of geostationary orbit (GEO) satellites have attracted increasing attention, and with the development of optical technologies, GEO optical satellites have become popular worldwide...In the past few decades, applications of geostationary orbit (GEO) satellites have attracted increasing attention, and with the development of optical technologies, GEO optical satellites have become popular worldwide. This paper proposes a general working pattern for a GEO optical satellite, as well as a target observation mission planning model. After analyzing the requirements of users and satellite control agencies, two objectives are simultaneously considered: maximization of total profit and minimization of satellite attitude maneuver angle. An NSGA-II based multi-objective optimization algorithm is proposed, which contains some heuristic principles in the initialization phase and mutation operator, and is embedded with a traveling salesman problem (TSP) optimization. The validity and performance of the proposed method are verified by extensive numerical simulations that include several types of point target distributions.展开更多
The sensible and latent heat fluxes over the ocean area near China were calculated and analyzed by usingthe Goddard Earth Observing System (GEOS) - four-dimensional Data Assimilation System (DAS). The calculated resul...The sensible and latent heat fluxes over the ocean area near China were calculated and analyzed by usingthe Goddard Earth Observing System (GEOS) - four-dimensional Data Assimilation System (DAS). The calculated results showed that the sensible heat flux had its large value in winter and autumn , small value in spring and summer overthe ocean area near China. In winter, the sensible heat flux increased distinctly with latitude, and its isolines were verycrowded. Over the ocean area east of Taiwan Province and south of Japan, the direction of isoline was from southwestto northeast. In the South China Sea the sensible heat flux was lower than that of surrounding ocean areas,and its isoline was distributed into a type of an inverted trough. In autumn and winter, the maximum center of latent heat flux appeared over the ocean area northeast of Taiwan Province and south and southeast of Japan, meanwhile, the isoline wasin the direction of southwest to northeast. In spring and summer, the latent heat flux had minimum value in the Huanghai Sea. At the same time, the maximum value center of latent heat flux appeared over the ocean area south of Japan inspring.展开更多
There are mounting evidences that human consume significant quantities of resources and have a major impact on the environment. Some research indicates that since the 1980s human demands on the biosphere have exceeded...There are mounting evidences that human consume significant quantities of resources and have a major impact on the environment. Some research indicates that since the 1980s human demands on the biosphere have exceeded its regen-errative capacity. One way to solve this problem is to minimize the inappropriate ex-ploitation from environment. This essay wil focus on energy self-sustained project, which is a specific way to reduce energy requirements. Energy self-sustained project refers to that energy production is equal to the amount consumed. Three concepts are quoted in the fol-lowing to assess whether the project achieve zero-energy or not. First, ecological footprint, which provides an indication of the human load on the biosphere, is uti-lized to measure the inputs and outputs of the bioregion, which is also beneficial for defining the potential energy. Another one is life cycle assessment, which evaluates environmental load that relates to the entire life periodic system of a product, is helpful to measure the products used in the energy self sustained project. In addi-tion, net energy, and gross resource abundance, definitions for selection, or hierar-chy of different energy resources, can evaluate the new energy resources in project. Geos Neighbourhood, located in colorado, was planned as the largest net-zero energy neighbourhood in the United States. To meet the energy self sustainability, earth and sun power completely sustain the community＇s energy needs, and re-place al fossil fuels. Compared with the traditional communities, Geos Neighbour-hood minimize the adverse impact on the environment. As tools for assessment, ecological footprint, life circle assessment, and net energy, are al used to analyse the planning and design principles in the neighbourhood. By the research, the de-sign principles and energy use in Geos Neighbourhood wil be re-examined that whether the zero energy project achieves the reduction of ecological footprint, and energy self sustainability. In addition, life circle assessment wil re-examine the ma-terials used in the community also. Final y, the concept of ＇net energy＇ wil test solar energy and earth power which is the major energy used in Geos Neighbour-hood.展开更多
The impacts of ionospheric scintillation on geosynchronous synthetic aperture radar（GEO SAR）focusing is studied based on the multiple phase screen（MPS）theory.The power spectrum density of electron irregularities i...The impacts of ionospheric scintillation on geosynchronous synthetic aperture radar（GEO SAR）focusing is studied based on the multiple phase screen（MPS）theory.The power spectrum density of electron irregularities is first modified according to the ionospheric anisotropy.Then propagation wave equations in random medium are deduced in the case of oblique incidence in GEO SAR.The amplitude and phase errors induced by the random electron fluctuations are generated by the iterated MPS simulations and are superimposed into the GEO SAR signals.Through the following imaging and evaluation,the effects of the anisotropic ionospheric scintallition on GEO SAR are assessed.At last,the optimized integration time under different ionospheric scintillation conditions are recommended through Monte Carlo experiments.It is concluded that,greater ionospheric fluctuations and longer integration time will result in more severe deterioration,even no focus at all in the worst case.展开更多
The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) s...The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) satellite network relays. According to the geographical distribution of the forthcoming Chinese Deep Space Measuring and Controlling Network (DSMCN), two networking schemes are proposed and two elevation angle optimization models are established for locating GEO relay satellites. To analyze the dynamic connectivity, a dynamic network model is constructed with respect to the time-varying characteristics of cislunar trunk links. The advantages of the two proposed schemes, in terms of the Connectivity Rate (CR), Interruption Frequency (IF), and Average Length of Connecting Duration (ALCD), are corroborated by several simulations. In the case of the lunar polar orbit constellation case, the gains in the performance of scheme I are observed to be 134.55%, 117.03%, and 217.47% compared with DSMCN for three evaluation indicators, and the gains in the performance of scheme II are observed to be 238. 22%, 240.40%, and 572.71%. The results validate that the connectivity of GEO satellites outperforms that of earth facilities significantly and schemes based on GEO satellite relays are promising options for cislunar multi-hop communication networking.展开更多
Collocating geostationary satellites sharing the same position is much demanded for satellite operation recently,the separation strategies are adopted to safeguard the satellites collocated of leaving the relative dis...Collocating geostationary satellites sharing the same position is much demanded for satellite operation recently,the separation strategies are adopted to safeguard the satellites collocated of leaving the relative distance beyond collision with different sets of orbit parameters.This paper presents the mathematical prototypes which establish the allowable relative distance with uncertainty of orbital determination(OD),as well as the orbital element offset for each pair of collocated satellites,and puts forward algorithms to build such relationship to face the challenge of putting three satellites sharing the same position,the algorithms to allocate the longitude,eccentricity and inclination for each satellite are also given to ascertain that the mathematical prototypes are the guide specification to design collocation strategy for geostationary satellites.展开更多
Based on its ability to obtain two-dimensional(2D)high-resolution images in all-time and all-weather conditions,spaceborne synthetic aperture radar(SAR)has become an important remote sensing technique and the study of...Based on its ability to obtain two-dimensional(2D)high-resolution images in all-time and all-weather conditions,spaceborne synthetic aperture radar(SAR)has become an important remote sensing technique and the study of such systems has entered a period of vigorous development.Advanced imaging modes such as radar interferometry,tomography,and multi-static imaging,have been demonstrated.However,current in-orbit spaceborne SARs,which all operate in low Earth orbits,have relatively long revisit times ranging from several days to dozens of days,restricting their temporal sampling rate.Geosynchronous SAR(GEO SAR)is an active research area because it provides significant new capability,especially its much-improved temporal sampling.This paper reviews the research progress of GEO SAR technologies in detail.Two typical orbit schemes are presented,followed by the corresponding key issues,including system design,echo focusing,main disturbance factors,repeat-track interferometry,etc,inherent to these schemes.Both analysis and solution research of the above key issues are described.GEO SAR concepts involving multiple platforms are described,including the GEO SAR constellation,GEO-LEO/airborne/unmanned aerial vehicle bistatic SAR,and formation flying GEO SAR(FF-GEO SAR).Due to the high potential of FF-GEO SAR for three-dimensional(3D)deformation retrieval and coherence-based SAR tomography(TomoSAR),we have recently carried out some research related to FF-GEO SAR.This research,which is also discussed in this paper,includes developing a formation design method and an improved TomoSAR processing algorithm.It is found that GEO SAR will continue to be an active topic in the aspect of data processing and multi-platform concept in the near future.展开更多
Rendezvous on the geostationary orbit(GEO)is much more complex than that on the low earth orbit and has a higher critical requirement for safety performance.This paper presents a safe scenario design method for GEO re...Rendezvous on the geostationary orbit(GEO)is much more complex than that on the low earth orbit and has a higher critical requirement for safety performance.This paper presents a safe scenario design method for GEO rendezvous proximity missions where the safety constraint of a collocated satellite is considered.A recently proposed quantitative index considering trajectory uncertainty is introduced to analyze the safety performance of the scenario parameters including the V-bar keeping positions and the fly-by trajectory radius.Furthermore,an exhaustive analysis is performed to find the dangerous regions of the V-bar keeping positions and the appropriate semi-major axis of the fly-by ellipse,considering the safety requirements of both the target and the collocated satellite.A geometry method is then developed for designing a feasible and suboptimal safe rendezvous scenario.The method is tested by designing four rendezvous scenarios with±V-bar approach directions respectively in the situations with and without one collocated satellite.Safety performance and velocity increments of the scenarios are compared and a conclusion is reached that the collocated satellite has a significant influence on the scenario design.展开更多
Geostationary satellites(GEOs) play a significant role in the regional satellite navigation system.Simulation experiments show that the clock corrections could be mitigated through a single strategy or double differen...Geostationary satellites(GEOs) play a significant role in the regional satellite navigation system.Simulation experiments show that the clock corrections could be mitigated through a single strategy or double differencing strategies for a navigation constellation,but for the mode of individual GEO orbit determination,high precision orbit and clock correction could not be obtained in the orbit determination based on the pseudorange data.A new GEO combined precise orbit determination(POD) strategy is studied in this paper,which combines pseudorange data and C-band transfer ranging data.This strategy overcomes the deficiency of C-band transfer ranging caused by limited stations and tracking time available.With the combination of transfer ranging and pseudorange data,clock corrections between the GEO and the stations can be estimated simultaneously along with orbital parameters,maintaining self-consistency between the satellite ephemeris and clock correction parameters.The error covariance analysis is conducted to illuminate the contributions from the transfer ranging data and the psudoranging data.Using data collected for a Chinese GEO satellite with 3 C-band transfer ranging stations and 4 L-band pseudorange tracking stations,POD experiments indicate that a meter-level accuracy is achievable.The root-mean-square(RMS) of the post-fit C-band ranging data is about 0.203 m,and the RMS of the post-fit pseudorange is 0.408 m.Radial component errors of the POD experiments are independently evaluated with the satellite laser ranging(SLR) data from a station in Beijing,with the residual RMS of 0.076 m.The SLR evaluation also suggests that for 2-h orbital predication,the predicted radial error is about 0.404 m,and the clock correction error is about 1.38 ns.Even for the combination of one C-band transfer ranging station and 4 pseudorange stations,POD is able to achieve a reasonable accuracy with the radial error of 0.280 m and the 2-h predicted radial error of 0.888 m.Clock synchronization between the GEO and tracking stations is achieved with an estimated accuracy of about 1.55 ns,meeting the navigation service requirements.展开更多
A spatial web portal(SWP)provides a web-based gateway to discover,access,manage,and integrate worldwide geospatial resources through the Internet and has the access characteristics of regional to global interest and s...A spatial web portal(SWP)provides a web-based gateway to discover,access,manage,and integrate worldwide geospatial resources through the Internet and has the access characteristics of regional to global interest and spiking.Although various technologies have been adopted to improve SWP performance,enabling high-speed resource access for global users to better support Digital Earth remains challenging because of the computing and communication intensities in the SWP operation and the dynamic distribution of end users.This paper proposes a cloud-enabled framework for high-speed SWP access by leveraging elastic resource pooling,dynamic workload balancing,and global deployment.Experimental results demonstrate that the new SWP framework outperforms the traditional computing infrastructure and better supports users of a global system such as Digital Earth.Reported methodologies and framework can be adopted to support operational geospatial systems,such as monitoring national geographic state and spanning across regional and global geographic extent.展开更多
基金supported by the National Natural Science Foundation of China(7150118061473301)
文摘In the past few decades, applications of geostationary orbit (GEO) satellites have attracted increasing attention, and with the development of optical technologies, GEO optical satellites have become popular worldwide. This paper proposes a general working pattern for a GEO optical satellite, as well as a target observation mission planning model. After analyzing the requirements of users and satellite control agencies, two objectives are simultaneously considered: maximization of total profit and minimization of satellite attitude maneuver angle. An NSGA-II based multi-objective optimization algorithm is proposed, which contains some heuristic principles in the initialization phase and mutation operator, and is embedded with a traveling salesman problem (TSP) optimization. The validity and performance of the proposed method are verified by extensive numerical simulations that include several types of point target distributions.
文摘The sensible and latent heat fluxes over the ocean area near China were calculated and analyzed by usingthe Goddard Earth Observing System (GEOS) - four-dimensional Data Assimilation System (DAS). The calculated results showed that the sensible heat flux had its large value in winter and autumn , small value in spring and summer overthe ocean area near China. In winter, the sensible heat flux increased distinctly with latitude, and its isolines were verycrowded. Over the ocean area east of Taiwan Province and south of Japan, the direction of isoline was from southwestto northeast. In the South China Sea the sensible heat flux was lower than that of surrounding ocean areas,and its isoline was distributed into a type of an inverted trough. In autumn and winter, the maximum center of latent heat flux appeared over the ocean area northeast of Taiwan Province and south and southeast of Japan, meanwhile, the isoline wasin the direction of southwest to northeast. In spring and summer, the latent heat flux had minimum value in the Huanghai Sea. At the same time, the maximum value center of latent heat flux appeared over the ocean area south of Japan inspring.
文摘There are mounting evidences that human consume significant quantities of resources and have a major impact on the environment. Some research indicates that since the 1980s human demands on the biosphere have exceeded its regen-errative capacity. One way to solve this problem is to minimize the inappropriate ex-ploitation from environment. This essay wil focus on energy self-sustained project, which is a specific way to reduce energy requirements. Energy self-sustained project refers to that energy production is equal to the amount consumed. Three concepts are quoted in the fol-lowing to assess whether the project achieve zero-energy or not. First, ecological footprint, which provides an indication of the human load on the biosphere, is uti-lized to measure the inputs and outputs of the bioregion, which is also beneficial for defining the potential energy. Another one is life cycle assessment, which evaluates environmental load that relates to the entire life periodic system of a product, is helpful to measure the products used in the energy self sustained project. In addi-tion, net energy, and gross resource abundance, definitions for selection, or hierar-chy of different energy resources, can evaluate the new energy resources in project. Geos Neighbourhood, located in colorado, was planned as the largest net-zero energy neighbourhood in the United States. To meet the energy self sustainability, earth and sun power completely sustain the community＇s energy needs, and re-place al fossil fuels. Compared with the traditional communities, Geos Neighbour-hood minimize the adverse impact on the environment. As tools for assessment, ecological footprint, life circle assessment, and net energy, are al used to analyse the planning and design principles in the neighbourhood. By the research, the de-sign principles and energy use in Geos Neighbourhood wil be re-examined that whether the zero energy project achieves the reduction of ecological footprint, and energy self sustainability. In addition, life circle assessment wil re-examine the ma-terials used in the community also. Final y, the concept of ＇net energy＇ wil test solar energy and earth power which is the major energy used in Geos Neighbour-hood.
基金Supported by the National Natural Science Foundation of China(61225005,61427802,61471038,61120106004)Chang Jiang Scholars Program(T2012122)+1 种基金111 project of China(B14010)Beijing Higher Education Young Elite Teacher Project(YETP1168)
文摘The impacts of ionospheric scintillation on geosynchronous synthetic aperture radar（GEO SAR）focusing is studied based on the multiple phase screen（MPS）theory.The power spectrum density of electron irregularities is first modified according to the ionospheric anisotropy.Then propagation wave equations in random medium are deduced in the case of oblique incidence in GEO SAR.The amplitude and phase errors induced by the random electron fluctuations are generated by the iterated MPS simulations and are superimposed into the GEO SAR signals.Through the following imaging and evaluation,the effects of the anisotropic ionospheric scintallition on GEO SAR are assessed.At last,the optimized integration time under different ionospheric scintillation conditions are recommended through Monte Carlo experiments.It is concluded that,greater ionospheric fluctuations and longer integration time will result in more severe deterioration,even no focus at all in the worst case.
基金supported by the National High Technology Research and Development Program of P.R.China under Grant No.2012 AA121604 the National Natural Science Foundation of China under Grants No.60902042,No.61170014,No.61202079+1 种基金 the National Research Foundation for the Doctoral Program of Higher Education of China under Grant No.20090006110014 the Foundation for Key Program of Ministry of Education of China under Grant No.311007
文摘The architecture of cislunar multi-hop communication networks, which focuses on the requirements of lunar full-coverage and continuous cislunar communications, is presented on the basis of Geosynchronous Orbit (GEO) satellite network relays. According to the geographical distribution of the forthcoming Chinese Deep Space Measuring and Controlling Network (DSMCN), two networking schemes are proposed and two elevation angle optimization models are established for locating GEO relay satellites. To analyze the dynamic connectivity, a dynamic network model is constructed with respect to the time-varying characteristics of cislunar trunk links. The advantages of the two proposed schemes, in terms of the Connectivity Rate (CR), Interruption Frequency (IF), and Average Length of Connecting Duration (ALCD), are corroborated by several simulations. In the case of the lunar polar orbit constellation case, the gains in the performance of scheme I are observed to be 134.55%, 117.03%, and 217.47% compared with DSMCN for three evaluation indicators, and the gains in the performance of scheme II are observed to be 238. 22%, 240.40%, and 572.71%. The results validate that the connectivity of GEO satellites outperforms that of earth facilities significantly and schemes based on GEO satellite relays are promising options for cislunar multi-hop communication networking.
基金supported by the National Hi-Tech Research and Development Program of China ("863"Project)(Grant No.2012AA7040015)
文摘Collocating geostationary satellites sharing the same position is much demanded for satellite operation recently,the separation strategies are adopted to safeguard the satellites collocated of leaving the relative distance beyond collision with different sets of orbit parameters.This paper presents the mathematical prototypes which establish the allowable relative distance with uncertainty of orbital determination(OD),as well as the orbital element offset for each pair of collocated satellites,and puts forward algorithms to build such relationship to face the challenge of putting three satellites sharing the same position,the algorithms to allocate the longitude,eccentricity and inclination for each satellite are also given to ascertain that the mathematical prototypes are the guide specification to design collocation strategy for geostationary satellites.
基金This work was funded in part by the National Natural Science Foundation of China under Grant Nos.61960206009,61971039,and 61971037the Distinguished Young Scholars of Chongqing(Grant No.cstc2020jcyj-jqX0008)+2 种基金the National Ten Thousand Talents Program‘Young Top Talent’(Grant No.W03070007)the Special Fund for Research on National Major Research Instruments(NSFC Grant Nos.61827901,31727901)the Young Elite Scientists Sponsorship Program by CAST(2017QNRC001).
文摘Based on its ability to obtain two-dimensional(2D)high-resolution images in all-time and all-weather conditions,spaceborne synthetic aperture radar(SAR)has become an important remote sensing technique and the study of such systems has entered a period of vigorous development.Advanced imaging modes such as radar interferometry,tomography,and multi-static imaging,have been demonstrated.However,current in-orbit spaceborne SARs,which all operate in low Earth orbits,have relatively long revisit times ranging from several days to dozens of days,restricting their temporal sampling rate.Geosynchronous SAR(GEO SAR)is an active research area because it provides significant new capability,especially its much-improved temporal sampling.This paper reviews the research progress of GEO SAR technologies in detail.Two typical orbit schemes are presented,followed by the corresponding key issues,including system design,echo focusing,main disturbance factors,repeat-track interferometry,etc,inherent to these schemes.Both analysis and solution research of the above key issues are described.GEO SAR concepts involving multiple platforms are described,including the GEO SAR constellation,GEO-LEO/airborne/unmanned aerial vehicle bistatic SAR,and formation flying GEO SAR(FF-GEO SAR).Due to the high potential of FF-GEO SAR for three-dimensional(3D)deformation retrieval and coherence-based SAR tomography(TomoSAR),we have recently carried out some research related to FF-GEO SAR.This research,which is also discussed in this paper,includes developing a formation design method and an improved TomoSAR processing algorithm.It is found that GEO SAR will continue to be an active topic in the aspect of data processing and multi-platform concept in the near future.
基金the National Natural Science Foundation of China(Grant Nos.11572345 and 11402257)the National Basic Research Program of China(973 Program,Grant No.2013CB733100).
文摘Rendezvous on the geostationary orbit(GEO)is much more complex than that on the low earth orbit and has a higher critical requirement for safety performance.This paper presents a safe scenario design method for GEO rendezvous proximity missions where the safety constraint of a collocated satellite is considered.A recently proposed quantitative index considering trajectory uncertainty is introduced to analyze the safety performance of the scenario parameters including the V-bar keeping positions and the fly-by trajectory radius.Furthermore,an exhaustive analysis is performed to find the dangerous regions of the V-bar keeping positions and the appropriate semi-major axis of the fly-by ellipse,considering the safety requirements of both the target and the collocated satellite.A geometry method is then developed for designing a feasible and suboptimal safe rendezvous scenario.The method is tested by designing four rendezvous scenarios with±V-bar approach directions respectively in the situations with and without one collocated satellite.Safety performance and velocity increments of the scenarios are compared and a conclusion is reached that the collocated satellite has a significant influence on the scenario design.
基金supported by the National High-Tech Research and Development Program of China (Grant No 2007AA12Z345)Space Navigation and Positioning Technique, Laboratory of Shanghai Municipality (Grant No 06ZD22101)Wuhan University Satellite Navigation and Positioning, Laboratory of the Ministry of Education (Grant No GRC-2009004)
文摘Geostationary satellites(GEOs) play a significant role in the regional satellite navigation system.Simulation experiments show that the clock corrections could be mitigated through a single strategy or double differencing strategies for a navigation constellation,but for the mode of individual GEO orbit determination,high precision orbit and clock correction could not be obtained in the orbit determination based on the pseudorange data.A new GEO combined precise orbit determination(POD) strategy is studied in this paper,which combines pseudorange data and C-band transfer ranging data.This strategy overcomes the deficiency of C-band transfer ranging caused by limited stations and tracking time available.With the combination of transfer ranging and pseudorange data,clock corrections between the GEO and the stations can be estimated simultaneously along with orbital parameters,maintaining self-consistency between the satellite ephemeris and clock correction parameters.The error covariance analysis is conducted to illuminate the contributions from the transfer ranging data and the psudoranging data.Using data collected for a Chinese GEO satellite with 3 C-band transfer ranging stations and 4 L-band pseudorange tracking stations,POD experiments indicate that a meter-level accuracy is achievable.The root-mean-square(RMS) of the post-fit C-band ranging data is about 0.203 m,and the RMS of the post-fit pseudorange is 0.408 m.Radial component errors of the POD experiments are independently evaluated with the satellite laser ranging(SLR) data from a station in Beijing,with the residual RMS of 0.076 m.The SLR evaluation also suggests that for 2-h orbital predication,the predicted radial error is about 0.404 m,and the clock correction error is about 1.38 ns.Even for the combination of one C-band transfer ranging station and 4 pseudorange stations,POD is able to achieve a reasonable accuracy with the radial error of 0.280 m and the 2-h predicted radial error of 0.888 m.Clock synchronization between the GEO and tracking stations is achieved with an estimated accuracy of about 1.55 ns,meeting the navigation service requirements.
基金Research reported is partially supported by NSF[grant numbers PLR-1349259 and IIP-1338925],FGDC[grant number G13PG00091],and NASA[grant number NNG12PP37I].
文摘A spatial web portal(SWP)provides a web-based gateway to discover,access,manage,and integrate worldwide geospatial resources through the Internet and has the access characteristics of regional to global interest and spiking.Although various technologies have been adopted to improve SWP performance,enabling high-speed resource access for global users to better support Digital Earth remains challenging because of the computing and communication intensities in the SWP operation and the dynamic distribution of end users.This paper proposes a cloud-enabled framework for high-speed SWP access by leveraging elastic resource pooling,dynamic workload balancing,and global deployment.Experimental results demonstrate that the new SWP framework outperforms the traditional computing infrastructure and better supports users of a global system such as Digital Earth.Reported methodologies and framework can be adopted to support operational geospatial systems,such as monitoring national geographic state and spanning across regional and global geographic extent.
