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Cloud detection methods for remote sensing images：a survey LIU Zili, YANG Jiajun, WANG Wenjing, SHI Zhenwei Chinese Space Science and Technology    2023, 43 (1): 1-17.   DOI: 10.16708/j.cnki.1000-758X.2023.0001 Abstract （1052）      PDF（pc） （3043KB）（1731）       Knowledge map     The cloud cover in the optical remote sensing images will obscure the ground information in different degrees，which causes the blurring and missing of the surface observation information and greatly affects the imaging quality of remote sensing images.Therefore，the detection and evaluation of cloud cover in remote sensing images are the basis and key to further analyze and utilize remote sensing image information.Through sufficient investigation and summary，the development trend and representative work of cloud detection methods based on remote sensing images at home and abroad since the 1990s were combed.Cloud detection methods based on remote sensing images were divided into three categories：methods based on band threshold，methods based on classical machine learning and methods based on deep learning.Besides，the public datasets at home and abroad used in the related research on cloud detection were summarized，and the accuracy of some representative cloud detection methods was compared.In addition to the vanilla cloud detection method，the cloud/fog（haze）detection，cloud/snow detection，cloud shadow detection and cloud removal methods related to cloud detection were also briefly combed.Based on the review and summary of cloud detection work above，the existing problems and future development trends of cloud detection were analyzed and prospected. Related Articles | Metrics

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Development status and prospect of satellite-based surveying YANG Yuanxi, WANG Jianrong, LOU Liangsheng, SUN Zhongmiao, XIAO Yun, MIAO Yuzhe Chinese Space Science and Technology    2022, 42 (3): 1-9.   DOI: 10.16708/j.cnki.1000-758X.2022.0031 Abstract （883）      PDF（pc） （918KB）（878）       Knowledge map    Satellite-based surveying is the main platform of global fundamental surveying, including satellite topographic survey, satellite gravimetry, satellite magnetic measuring, satellite altimetry, etc. The developments of satellite-based measuring projects have experienced “return type measuring satellite project”, “transmission type measuring satellite project” and some of “loads integration measuring satellite project”. This paper firstly reviews the development history and current situation of international satellite-based surveying projects, then analyzes the roles of China′s satellite-based surveying projects in various stages, including some existing problems. Finally, the ideas for the future development of satellite-based surveying are put forward. Related Articles | Metrics

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Advances and prospects of the configuration design and control research of the LEO mega-constellations RUAN Yongjing, HU Min, YUN Chaoming Chinese Space Science and Technology    2022, 42 (1): 1-15.   DOI: 10.16708/j.cnki.1000-758X.2022.0001 Abstract （844）      PDF（pc） （4662KB）（2149）       Knowledge map    In recent years, the LEO constellation programs have developed rapidly and become a “new battlefield” in the global competition of space strategic resources. Firstly, up-to-date status of LEO megaconstellations was described, and the current status of LEO mega-constellations in China was introduced. Configuration design methods and characteristics of constellation were summarized from four aspects, including mission requirements, coverage characteristics, perturbation compensation and spare strategy. Then, according to the whole control process of satellite constellations configuration from orbit to departure, the methods and characteristics of initialization control, stationkeeping control, reconfiguration control, constellation collision avoidance control and de-orbit control were reviewed. Finally, the future research aspects of the configuration design and configuration control technology of the LEO mega-constellations were looked into. Related Articles | Metrics

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Space robotic manipulation: a multi-task learning perspective LI Linfeng, XIE Yongchun Chinese Space Science and Technology    2022, 42 (3): 10-24.   DOI: 10.16708/j.cnki.1000-758X.2022.0032 Abstract （732）      PDF（pc） （3443KB）（522）       Knowledge map    It is a technological development trend in recent years to apply space robot in place of spaceman to perform on-orbit service tasks. Using deep neural network controller, the learning-based space robotic manipulation has shown good potential in adaptability to the unstructured space environments and applicability in fileds such as high earth orbit, extraterrestrial planet exploration, etc. At present, a large number of studies focus on single task robotic manipulation learning problems, for either onground robots or in-space robots. From a new perspective of multi-task learning, a thorough literature review on multi-task robot learning was made, including algorithms and robotic applications therein. To further apply the state-of-the-art multi-task robot learning algorthms, main technical challenges were analyzed and suggestions on key technology development were given. The breakthrough of the above challenges will increase the overall autonomy and robustness level of the space robot system, which is expected to further facilitate the development of China′s on-orbit service towards completely unmanned autonomy. Related Articles | Metrics

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Case study of inorbit satellite failures and artificial intelligence based failure detection WANG Yakun, YANG Kaifei, ZHANG Jie, GUO Lifang, HAN Xiaodong, XING Chuan, WANG Rui Chinese Space Science and Technology    2022, 42 (1): 16-29.   DOI: 10.16708/j.cnki.1000-758X.2022.0002 Abstract （697）      PDF（pc） （1709KB）（620）       Knowledge map    Reducing satellite failures and keeping satellites healthy in orbit are important issues in satellite design. In order to analyze the causes of satellite failures and explore the latest satellite failures detection methods, we first collected typical satellite fault cases in orbit from 2003 to 2021, and then performed statistical analysis and correlation analysis of satellite failures from different aspects, including the correlation between satellite platforms and satellite failures, and the relationship between satellite in-orbit time and satellite failures, etc. Finally, the artificial intelligence based satellite failures detection research was introduced, including the artificial intelligence based failures detection systems and methods as well as the time-series data failures detection research. This research can provide reference for future failure case analysis and failure detection system design of satellite. Related Articles | Metrics

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Review and prospect of intelligent perception for non-cooperative targets MU Jinzhen, HAO Xiaolong, ZHU Wenshan, LI Shuang Chinese Space Science and Technology    2021, 41 (6): 1-16.   DOI: 10.16708/j.cnki.1000-758X.2021.0076 Abstract （616）      PDF（pc） （1102KB）（1445）       Knowledge map    Intelligent perception is the key technology to realizing the fine control process of spacecraft on-orbit, which is one of the major development directions of on-orbit intelligence service. The key technologies of space target intelligent perception include pose measurement, three-dimensional reconstruction and component recognition, which involve the issues such as few-shot, multi-modality, model adaptation and high-dimensional data. From the perspective of engineering application, the latest research progress in the non-cooperative intelligent perception technique was systematically summarized. Firstly, the research status of the representative non-cooperative on-orbit perception systems and optical sensors were reviewed. Secondly, the key technologies involved in the intelligence perception of non-cooperative targets were analyzed. Finally, according to the analysis of the research status and critical techniques, the main issues of non-cooperative target intelligent perception were discussed, and the recommendations for the further development were presented. Related Articles | Metrics

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Analysis of the first stage deployment of Starlink constellation based on TLE XUE Wen, HU Min, RUAN Yongjing, YUN Chaoming, SUN Tianyu Chinese Space Science and Technology    2022, 42 (5): 24-33.   DOI: 10.16708/j.cnki.1000-758X.2022.0064 Abstract （563）      PDF（pc） （7069KB）（574）       Knowledge map     In recent years，with the rapid development of satellite technology and the increasing demand for low earth orbit（LEO）satellite broadband internet construction，the development of LEO large-scale constellations is changing rapidly.Aiming at the initial deployment of Starlink constellation，firstly，the current status of the Starlink constellation was discussed，and the altitude changes of orbiting satellites were analysed.Then，the deployment of the Starlink constellation was briefly analyzed from two aspects by utilizing the public two-line element（TLE），including satellite being launched into orbit and orbital plane distribution，and the changing rule of ascending node was given.At the same time，the ground coverage performance of the Starlink constellation was simulated and analyzed.Finally，the constellation orbital planes and phase distribution，handling of the faulty satellites，and the number of visible satellites were obtained.The results of the analysis are expected to provide reference for China′s future deployment of large-scale LEO constellations. Related Articles | Metrics

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Progress and prospect in planetary exploration of solar system YANG Mengfei, ZHENG Yanhong, NI Yanshuo, HUANG Xiaofeng, ZHANG Zhengfeng, XING Zhuoyi Chinese Space Science and Technology    2023, 43 (5): 1-12.   DOI: 10.16708/j.cnki.1000-758X.2023.0063 Abstract （525）      PDF（pc） （10199KB）（695）       Knowledge map    Planetary exploration is an important means of humans to understand the universe.With the continuous development of space technology，major space countries have carried out more than 100 planetary exploration activities in the solar system.Humans have realized the flyby，orbiting，lander，rover and sample return missions of solar system.Based on the implemented planetary exploration activities and upcoming missions，the main scientific issues and discoveries of planetary exploration were summarized.And the development tendency of planetary exploration was analyzed.According to the recent development plan of planetary exploration in China，a medium to longterm conceiving route and flagship mission have been proposed.It can provide support for the planning of future planetary exploration missions in China. Related Articles | Metrics

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Research status and prospect of modular space deployable and foldable mechanism TIAN Dake, GAO Haiming, JIN Lu, LIU Rongqiang, MA Xiaoou, FAN Xiaodong, GUO Zhenwei Chinese Space Science and Technology    2021, 41 (4): 16-31.   DOI: 10.16708/j.cnki.1000-758X.2021.0047 Abstract （520）      PDF（pc） （19796KB）（624）       Knowledge map    The modular space deployable and foldable mechanism has the characteristics of flexible expansion, good versatility and strong adaptability, which can meet the needs of large and ultralarge space deployable and foldable mechanism for major aerospace projects in China, such as long-distance deep space exploration, long-term in-orbit space station construction and ultra wide area satellite communication, and it is a new key aerospace equipment. According to the application requirements, the research progress of space modular deployable and foldable mechanism was described. The typical modular configurations of three types of deployable and foldable mechanism, such as deployable mast, solar array and space deployable antenna, were mainly introduced. The structure composition, deployment principle, driving mode and application status of modular space deployable and foldable mechanism were analyzed. The future development direction of space modular deployable and foldable mechanism was prospected from four aspects: mechanism innovative design method, ground microgravity test and simulation, space inorbit assembly technology and space inorbit construction technology. The review provides a reference for the research and application of large space deployable and foldable mechanism in China. Related Articles | Metrics

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Research of thrust measurement for space electric propulsion ZHANG Lupeng, YANG Xin, CHANG Lei, XU Qian, ZHOU Haishan, LUO Guangnan Chinese Space Science and Technology    2022, 42 (3): 25-38.   DOI: 10.16708/j.cnki.1000-758X.2022.0033 Abstract （514）      PDF（pc） （8286KB）（837）       Knowledge map     Accurate measurement of thrust is very important in the development and planning of space electric propulsion.In recent years,with the increasing of complexity and task difficulty for electric propulsion,higher requirements are put forward for the evaluation techniques and methods of thrust performance.In response to this demand,a review of the thrust measurement for space electric propulsion was presented.Measurement methods and the underlying mechanisms,technical features and applications were covered.The methods of thrust measurement can be divided into direct measurement and indirect measurement.The former mainly includes balance structure,torsional pendulum,suspension and inverted pendulum,while the latter mainly includes target and cantilever beam.The advantages and disadvantages of these measurement methods were summarized and compared,which provided a reference for developers to design the thrust measuring system.The key problems in the five segments including system design,system calibration,system response,system response measurement and calculation of thrust during the process of thrust measurement were described in detail,and the corresponding improvement methods were proposed.To serve as a reference for future thrust measurement research,suggestions were also provided by considering the development trend of electric propulsion and its demand of thrust measurement. Related Articles | Metrics

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Research progress and prospect of spacecraft reconfiguration technology PENG Qibo, WU Xinfeng, WANG Beichao, LI Shuang Chinese Space Science and Technology    2023, 43 (2): 16-31.   DOI: 10.16708/j.cnki.1000-758X.2023.0017 Abstract （503）      PDF（pc） （6523KB）（649）       Knowledge map     Spacecraft reconfiguration technology is the key technology that must be broken through for the in-orbit service of spacecraft and other major space missions，having a profound effect on the design，research and development of new spacecraft systems.Firstly，the connotation and classification of the spacecraft reconfiguration were presented.Then，the domestic and overseas research status of the technology was systematically concluded and discussed based on main structure reconfiguration and other typical technologies.Next，the system of the spacecraft reconfiguration technology was proposed based on the methods such as standardized modular design，and then application prospects were summarized in the aspects such as supporting fault elimination of spacecraft.Finally，overall research progress of the reconfiguration technology was concluded，and future development was also expected. Related Articles | Metrics

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BF-1 satellite system design and technology characteristics BAI Zhaoguang, WANG Chongyu, FAN Dongdong, SUN Jiwen Chinese Space Science and Technology    2022, 42 (2): 108-116.   DOI: 10.16708/j.cnki.1000-758X.2022.0028 Abstract （483）      PDF（pc） （8151KB）（125）       Knowledge map    BF-1 is the first meteorological satellite based on global navigation satellite system-reflection (GNSS-R) signal measurement technology in China, The new L-band sea surface wind field information detection technology was adopted to provide services for national meteorology, disaster prevention and mitigation and other industries in wind field measurement and sea surface hurricane wind speed inversion. From the perspective of system design, the overall technical indicators of BF-1 satellite were introduced, and the recognition process and results of the satellite system configuration, the key index of the load and the orbital characteristics in combination with the demand analysis were expounded. The technical characteristics of filling the gap of sea surface highprecision wind field monitoring, the first sea launch, satellite ground integrated data inversion, innovative data center and so on were summarized. The wind speed measurement accuracy can reach 2m/s while the wind field measurement is available in the range from 2m/s to 70m/s.  At the same time, the on-orbit test, load performance comparison and follow-up development suggestions were introduced. The design process can be used as a demonstration of subsequent operational satellites and other satellite systems. Related Articles | Metrics

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Technical project of ion propulsion for satellites in super low Earth orbit  YANG Fuquan, WANG Chengfei, HU Jing, ZHANG Hong, WU Chenchen, ZHANG Xingmin, GENG Hai, FU Danyin Chinese Space Science and Technology    2021, 41 (3): 52-59.   DOI: 10.16708/j.cnki.1000.758X.2021.0038 Abstract （463）      PDF（pc） （3138KB）（589）       Knowledge map    The Earth's outer atmosphere at the low altitude causes a significant drag on the spacecraft such as scientific detection and Earth observationsatellites in super low earth orbit, furthermore the atmospheric drag changes in a wide range along with solar activity, geomagnetic activity, seasonal and diurnal cycle. In order to meet the demands for satellite orbit accuracy or flight conditions, this drag needs to be continuously or intermittently compensated by onboard thrusters. Considering drag free flight and orbit maintenance at an altitude of about 220~268km, the variety of atmospheric drag and the specifications of the spacecraft payloads were analyzed, and then the researches were carried out on the technical parameters, thrust throttling approaches, system architecture, thrust control project and onorbit application strategy of ion propulsion. Accordingly thrust throttling tests were executed .The results show that ion propulsion should operates over a thrust range of 1~20mN with the thrust resolution of 12μN, and over a thrust range of 1~25mN with the thrust resolution of 100μN for drag free and orbit maintenance mission respectively.The technical project of ion propulsion is valuable for application reference of satellites in super low Earth orbit.  Related Articles | Metrics

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Research progress and prospect of on-orbit additive manufacturing technology LIU Jie, SHI Yun, CUI Yutao, HOU Juan, ZHANG Kai, HUANG Aijun Chinese Space Science and Technology    2022, 42 (6): 23-34.   DOI: 10.16708/j.cnki.1000-758X.2022.0080 Abstract （443）      PDF（pc） （5450KB）（499）       Knowledge map    In-space additive manufacturing technology is a “space 3D” printing technology，which has attracted major attention due to its application in on-orbit manufacturing and space base additive manufacturing.The basic concepts were introduced and the progress of space on-orbit additive manufacturing technology in the world was summarized.With the requirement of space stations and on-orbit spacecraft，the significant challenge of in-space additive manufacturing was the raw materials，printing technology and equipment.This was attributed to the unique feature of the space environment，including microgravity and high vacuum，etc. Finally，based on the current development status，requirements，and possible implementation paths of in-space onorbit manufacturing technology，the development direction of in-space additive manufacturing was pointed out. Related Articles | Metrics

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Research on omnidirectional ambiguity characteristics and calculation method of spaceborne SAR TAO Manyi, HU Guangqing, HUANG Yuanbao, CHEN Guozhong, SU Xiaoming Chinese Space Science and Technology    2022, 42 (1): 92-98.   DOI: 10.16708/j.cnki.1000-758X.2022.0010 Abstract （430）      PDF（pc） （4954KB）（365）       Knowledge map    The conventional ambiguity calculation method of spaceborne SAR is based on range one-dimensional pattern and azimuth one-dimensional pattern, and the range ambiguity and azimuth ambiguity are analyzed independently. However, the azimuth ambiguity is based on range ambiguity signal, which is caused by image processing. In order to solve the problem that the estimated range ambiguity value in system design is inconsistent with the actual imaging effect and to restore the essence of azimuth ambiguity, a new method of ambiguity analysis and calculation for spaceborne SAR was proposed. Firstly, the causes of range and azimuth ambiguity and the relationship between them were analyzed. Then, the range conversion model between the arbitrary pointing angle of the pattern and the actual observation to the earth was established. At the same time, based on the twodimensional pattern, the calculation method and steps of the omnidirectional ambiguity were given. Finally, the simulation design was carried out and the results show that the omnidirectional ambiguity calculation method is more in line with the actual imaging effect, providing a reference for the subsequent high-resolution spaceborne SAR system design and ambiguity suppression.  Related Articles | Metrics

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Progress and prospect of lunar resources exploitation and utilization YANG Mengfei, ZOU Zhigang, WANG Weihua, YAO Wei, WANG Qinggong Chinese Space Science and Technology    2024, 44 (1): 1-10.   DOI: 10.16708/j.cnki.1000-758X.2024.0001 Abstract （429）      PDF（pc） （4467KB）（553）       Knowledge map    With the implementation of the Chang′E-5 mission in 2020，the three phases of China lunar exploration program，namely orbiting，landing and returning，have been completed.Next，the International Lunar Research Station（ILRS）will be established at the lunar south pole by 2030，and a lunar base will be planned later.It is a new era of exploitation and utilization of the Moon，in which a vast tasks should be completed.In this paper，we summarized some important progresses of investigation of lunar resources in the past，including lunar resource exploration，analysis of lunar volatiles，mineral extraction，and material construction by 3D printing of lunar regolith.Then，we proposed future tasks for the exploitation of the lunar resources.The main challenges of the Moon，such as the extreme lunar environment，unique properties of lunar regolith，and autonomous control of the process，were considered.The views in this paper can be referenced for future scientific researches and engineering tasks in the field. Related Articles | Metrics

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Progress and prospect of solar exploration in space YANG Mengfei, DAI Shuwu, WANG Ying, ZHU Chenglin, YANG Shangbin, ZHANG Yechi Chinese Space Science and Technology    2022, 42 (5): 1-10.   DOI: 10.16708/j.cnki.1000-758X.2022.0062 Abstract （413）      PDF（pc） （2853KB）（402）       Knowledge map     In order to explore the development direction of solar space exploration activities，ten typical probes were selected taking into account their implementation era，orbital design，exploration elements，technical characteristics and each mission′s result based on extensive research on solar probe missions.Scientific objectives，payloads，satellite platform characteristics and scientific achievements of the ten typical probes were analyzed.Solar space exploration progress and development trend were summarized.In general，the orbit of solar detectors has been gradually diversified，detection elements of payload have become more abundant，and the detection accuracy and resolution have been significantly improved.However，there are still a lot of problems to be solved.On the basis of analyzing the current achievements and pending problems，the development outlook of solar space exploration was proposed，pointing out that all round and multielement exploration is a feasible way to break the bottleneck of solar physics and space weather forecast. Related Articles | Metrics

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Domain control strategy for the large-scale satellite cluster LI Ning, YUE Chengfei, GUO Haibo, QIU Shi, CAO Xibin Chinese Space Science and Technology    2023, 43 (1): 18-28.   DOI: 10.16708/j.cnki.1000-758X.2023.0002 Abstract （393）      PDF（pc） （6485KB）（483）       Knowledge map    In large-scale satellite constellations，single node management and control will lead to poor system connectivity and high dependence on ground resources.A distributed domain control strategy for satellite constellations with hierarchical management，intradomain autonomy and dynamic maintenance was proposed.Firstly，both the static index and dynamic index to measure the governability were defined.According to the newly-defined indexes，a multi-factor weighted cluster head selection method was proposed.Then，based on the selected cluster head node，a cascading optimal initialization algorithm of the cluster was established.Aiming at dynamic maintaining of the established cluster control structure，an event-triggered dynamic time slice domain control method was proposed.Finally，control simulation result of the proposed method in the case of LEO large-scale satellite constellation verifies the effectiveness of cluster head selection，cluster initialization and long-time maintaining.The number of satellites which were managed through ground station was reduced to 14%.High dependence on ground resources was resolved. Related Articles | Metrics

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Intelligent program synthesis framework and key scientific problems for embedded software YANGMengfei, GUBin, DUANZhenhua, JINZhi, ZHANNaijun, DONGYunwei, TIANCong, LIGe, DONG Xiaogang , LIXiaofeng Chinese Space Science and Technology    0, (): 1-7.   DOI: 10.16708/j.cnki.1000-758X.2022.0046 Abstract （388）      PDF（pc） （2052KB）（296）       Knowledge map    Program synthesis is an effective way to improve the efficiency of software development and the quality of software，and it is one of the most challenging problems in computer science.Firstly，the research status and existing problems of program synthesis methods were reviewed.Secondly，the concept of software IP（intellectual property）and an embedded software intelligent synthesis development method based on software IP（IP based embedded software intelligent synthesis，IPESIS）with its framework were proposed.Finally，the key scientific problems and main research contents that IPESIS needs to solve were discussed.IPESIS describes software requirement at a higher level of abstraction by defining the domain requirement description language，reduces the program search space with software IP as the granularity，and uses machine learning and other artificial intelligence technologies to automatically synthesize programs.It is expected to break through the limitations of existing methods，and then realize the transition of embedded software development from manual programming to software IP research and development plus intelligent synthesis based on software IP. Related Articles | Metrics

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Resource allocation in high throughput multibeam communication satellite systems WANG Lei, ZHENG Jun, HE Chuan, YAN Xuefei Chinese Space Science and Technology    2021, 41 (5): 85-94.   DOI: 10.16708/j.cnki.1000-758X.2021.0070 Abstract （384）      PDF（pc） （3765KB）（782）       Knowledge map    Resource allocation plays an important role in the performance of new generation of high throughput multibeam communication satellite(HTMCS) systems. The static and single dimension methods for resource allocation were normally proposed for previous communication satellite systems with non-flexible payloads and uniform distribution of users’ capacity demands, which has seriously constrained the performance of the HTMCS systems. A joint power and bandwidth resource allocation model for the HTMCS systems was built, with the consideration for beam interference, flexible payloads and nonuniform distribution of capacity demands. Meanwhile, a genetic algorithm with high efficient search control strategies was implemented to solve this model. Finally, several types of dataset were employed with different capacity demands and distribution profile between beams to verify the proposed method. Experimental results show that the method can reduce the unmet capacity demand(UCD) by 71.09%, 40.47% and 16.31% compared to the current static method for the total capacity demand of 90Gbit/s, 110Gbit/s and 130Gbit/s respectively. Related Articles | Metrics