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Orbit design method of near-lunar space constellation CHEN Shiyu, NI Yanshuo, PENG Jing Chinese Space Science and Technology    2024, 44 (3): 15-29.   DOI: 10.16708/j.cnki.1000-758X.2024.0035 Abstract （2220）      PDF（pc） （9757KB）（2611）       Knowledge map     According to the requirements of relay communication and lunar navigation for future lunar exploration missions，an orbit design method of near-moon space constellation is proposed.First，the indexes of constellation design in relay communication，lunar navigation，cost for deployment and maintenance are sorted out，and analytic hierarchy process is applied to determine the weights of the indexes so that a comprehensive evaluation index can be proposed.The properties of various types of orbits are analyzed with full consideration of orbit resources near the moon，and the orbit types suitable for constellation deployment are initially screened.A construction route of the near-moon space constellation is proposed，where 100% quadruple cover for the whole moon is gradually realized in three stages.The constellation configurations in the three stages are designed successively.For each stage，different configurations are compared and the one with the best comprehensive evaluation index is selected.Based on the above method，the construction scheme of the constellation in near-moon space is obtained.In the first stage，2 satellites are deployed in elliptical lunar frozen orbit（ELFO）to provide full-time earth relay communication for the south pole region of the moon.In the second stage，6 ELFO satellites，2 near rectilinear halo orbit（NRHO）satellites，and 1 L2 halo orbit satellite are deployed to provide full-time navigation for the south pole region and fulltime earth communication for the entire lunar surface.In the third stage，4 ELFO satellites，2 NRHO satellites，1 L1 halo orbit satellite，and 3 distant retrograde orbit satellites are deployed to provide full-time navigation for the entire lunar surface.For any position in the whole lunar surface，the geometric dilution of precision of the designed constellation keeps below 5 in at least 72% of the time，leading to a long-term high-precision navigation for the whole lunar surface.Compared with the existing literature，the proposed design method of the near-lunar space constellation considers more orbit types，more comprehensive constellation performance indexes，and innovatively puts forward a phased construction scheme of the near-lunar space constellation. Related Articles | Metrics

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Architecture and development envision of cislunar space infrastructure YANG Mengfei, PENG Jing, LI Jionghui, NI Yanshuo, ZHU Shunjie, DU Ying, XU Baobi, HUANG Xiaofeng, ZHANG Zhengfeng Chinese Space Science and Technology    2024, 44 (3): 1-14.   DOI: 10.16708/j.cnki.1000-758X.2024.0034 Abstract （1811）      PDF（pc） （7344KB）（2059）       Knowledge map    The construction of cislunar space infrastructure（CLSI）can provide basic and universal services for human activities in the cislunar space，including data communications，position navigation and timing（PNT），and situation monitoring for the development of lunar space，which can meet the needs of follow-up major national lunar exploration projects.At the same time，it has strategic significance for accelerating the development of the space industry into the cislunar space，and promoting China′s strength in science，technology and aerospace.On the basis of clarifying the concept of CLSI and analyzing the state-of-art development status，the top-level system architecture is proposed for the CLSI，addressing to the needs of major projects and the sustainable development of the aerospace industry.Then，the system services，the system composition，the “cloud-domain-end” network architecture as well as the internal and user interfaces architecture are defined and demonstrated.Finally，with the goal of gradually establishing a technologically advanced and reasonably deployed CLSI by phases and providing universal services that are open，safe，reliable，and operate continuously and stably in the long term，development prospects and suggestions are proposed to provide reference for the development and construction planning of CLSI. Reference | Related Articles | Metrics

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Review on spacecraft autonomous decision-making and planning for orbital threat avoidance GAO Wanying, WU Jianfa, WEI Chunling Chinese Space Science and Technology    2024, 44 (4): 71-89.   DOI: 10.16708/j.cnki.1000-758X.2024.0059 Abstract （440）      PDF（pc） （2018KB）（1014）       Knowledge map    The accumulation of space debris，the deployment of large-scale satellite constellations，and intensified spatial competition have led to a rapid increase in the number of orbital threats，seriously threatening the safety and stability of spacecraft.Research into spacecraft autonomous decision-making and planning for orbital threats is crucial to securing China's space assets.Confronted with complex scenarios characterized by high dynamics，time-varying constraints，incomplete or imperfect information，and multiple concurrent threats，this research faces several practical challenges.This review examines the research status of spacecraft autonomous decision-making and planning，discusses key technologies including problem modeling，decision-making，maneuver planning，intelligent decision-making and planning，and concludes with suggestions for future research. Related Articles | Metrics

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System design and key technologies of No.4 land exploration satellite 01 ZHANG Qingjun, NI Chong, DAI Chao, LIU Liping, TANG Zhihua, SHU Weiping Chinese Space Science and Technology    2025, 45 (1): 1-11.   DOI: 10.16708/j.cnki.1000-758X.2025.0001 Abstract （935）      PDF（pc） （8217KB）（893）       Knowledge map    In order to solve the problem of small imaging width and long revisiting time of low orbit SAR,China developed the No.4 land exploration satellite 01,which is a scientific satellite in the medium and long term development plan of national civil space infrastructure (2015-2025),and is the world′s first geosynchronous SAR satellite.Using the advantages of the geosynchronous orbit,the revisiting time of the same place can be reduced from the day level of low orbit satellite to the hour level,and the width can be increased from the hundred-kilometer level of low orbit satellite to the thousand-kilometer level,which can provide strong support for the effective implementation of disaster emergency response.For the new system of geosynchronous SAR microwave imaging,a series of key technologies are developed,such as microwave imaging for geosynchronous SAR,ultra-large power space-borne microwave transmission,ultra-large aperture space-borne antenna,large-flexibility and high-precision attitude stability control,intense pulse high-quality large power supply,integrated efficient thermal management for payload and platform,and integrated satellite-ground high-precision orbit determination.The satellite has the capability of quick revisit,large width,all-day and all-weather observation.The overall design of the satellite is introduced,and the technical innovation is summarized.Through the evaluation of the preliminary test results for the satellite in orbit,the geosynchronous SAR images have clear texture and good quality,which can meet the requirements of disaster prevention and reduction,land resource exploration and other tasks. Related Articles | Metrics

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System design and validation of Queqiao-2 lunar relay communication satellite ZHANG Lihua, XIONG Liang, SUN Ji, CHEN Luojing, XIAO Chuan, ZHOU Wenyan, WANG Yong, LIU Wangwang, GUAN Yifeng, CHEN Tao, YU Xiaochuan, XU Jin, CHEN Guohui, CAO Xiaoping Chinese Space Science and Technology    2024, 44 (5): 23-39.   DOI: 10.16708/j.cnki.1000-758X.2024.0071 Abstract （751）      PDF（pc） （8335KB）（799）       Knowledge map    In order to provide relay communication supports for future Chinese lunar exploration program，Queqiao-2 relay communication satellite was developed.Queqiao-2 can perform scientific observations with three kinds of scientific instruments on board.The system design of Queqiao-2，including mission orbit and transfer orbit design，configuration and layout design，housekeeping and information flow design，power supply and distribution design，GNC and propulsion system design，communication links design，etc.，was accomplished through comprehensive tradeoff and evaluation on technical maturity，availability，schedule，cost，and so on.With a view to reducing development risk，both the platform and relay communication payloads were developed based on significant heritage from previous Queqiao relay satellite and other relevant spacecraft.Queqiao-2 features flexible system architecture to support multiple frequencies，modulations，data rates and software reconfigurations to meet new user requirements.Subsequent to a successful launch on March 20，2024，by means of 5 orbit maneuvers，Queqiao-2 was inserted into a highly elliptical frozen mission orbit around the moon with a 24h period on schedule.Following on-orbit tests and calibrations，Queqiao-2 has possessed the capacity to provide reliable relay communication services to multiple lunar exploration missions，as well as the capacity to perform scientific observations.Under the support of Queqiao-2，Chang′e-6 achieved its ambitious mission goal to collect  and return samples from the moon′s mysterious far side.In the meanwhile，Queqiao-2 has also paved the way for the following Chinese lunar exploration missions including Chang′e-7 and Chang′e-8.The design life time of Queqiao-2 is more than 8 years.Benefit from flexibility and extensibility of relay communication system design，it is convenient to provide relay communication services for future lunar exploration missions of both China and other countries.In addition，innovative scientific observations would be performed during the period that no relay communication task is arranged.The system design of Queqiao-2 reflects the development philosophy of technical innovations and inheritance integration.Based on highly flexible and extensible system architecture，multiple and concurrent relay communication mission requirements can be met.It can provide strong supports for future lunar exploration missions.Successful launching，orbit entering and on-orbit tests of Queqiao-2 verified the correct design principle and versatility.By means of Queqiao-2，more innovative scientific outcomes are anticipated and lunar exploration activities can be facilitated. Related Articles | Metrics

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Review of space target positioning algorithms based on space-based optical detection LI Yao, CHEN Xin, RAO Peng Chinese Space Science and Technology    2024, 44 (2): 1-15.   DOI: 10.16708/j.cnki.1000-758X.2024.0017 Abstract （555）      PDF（pc） （6075KB）（1343）       Knowledge map    In recent years，the field of space target localization has developed rapidly by integrating detection technologies such as sensor-network collaboration and multi-mode fusion.Positioning methods based on space-based optical detection are widely used in civil and national defense fields with their unique advantages of good concealment and high measurement accuracy.In order to analyze the localization methods suitable for different types of spatial targets in different scenarios，small space target positioning methods based on space-based optical detection were reviewed.Firstly，the development of space-based optical detection technology，the classification and characteristics of space targets，and the concept of space target localization were introduced.Secondly，the positioning methods based on single satellite or multi-satellites suitable for small and weak spatial targets were analyzed.The joint positioning of heterogeneous sensors proposed in recent years was explained.Besides，the error analysis model of spatial target positioning was established according to the imaging process.The proportion of factors influencing positioning accuracy was analyzed.Finally，the summary and outlook were made based on the existing problems. Related Articles | Metrics

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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 （1667）      PDF（pc） （2660KB）（2626）       Knowledge map    The cloud cover in the optical remote sensing images will obscure the ground information to varying degrees，which causes the blurring and loss 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 analyzing and utilizing 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 reviewed.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 standard cloud detection methods，the cloud and fog（haze）detection，cloud and snow detection，cloud shadow detection and cloud removal methods related to cloud detection were also briefly reviewed.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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Analysis and key design of lunar far-side robotic sampling and return misson SHENG Ruiqing, MENG Zhanfeng, ZHAO Yang, TAN Zhiyun, ZHANG Hong, HUANG Hao, ZHANG Wu Chinese Space Science and Technology    2024, 44 (5): 1-14.   DOI: 10.16708/j.cnki.1000-758X.2024.0069 Abstract （786）      PDF（pc） （17095KB）（615）       Knowledge map    The Chang′e-6 lunar probe is designed to achieve the first robotic sampling and return mission from the far side of the Moon.The lunar far side has rugged terrain overall and lacks flat areas suitable for sampling.Two areas in Apollo basin within south pole Atiken basin （SPA）are selected as primary and backup targeted landing sites，the safety and reliability of landing，lift-off and surface operation process are ensured.In order to achieve new mission objectives within the establis hed technical configuration，an optimal system design solution is put forward to reduce system changes.The risks associated with alterations of technical status are avoided.Through comparative analysis，a retrograde orbit around the Moon is selected，ensuring minimal system modifications and optimal system design.In consideration of the reduced and discontinuous duration of relay telemetry and control on the far side of the Moon for Chang′e-6，a phased，highly autonomous，and cooperative relay-assisted lunar surface operation timeline design is proposed to ensure the implementation during landing，lift-off and surface operation process.For payload carried by Chang′e-6，a system design is proposed by using data processing units as the central exchange hub to ensure electrical interface safety isolation；customized detection modes are also developed for different payloads to maximize detection benefits without affecting the completion of the main mission.These methods are applied in the Chang′e-6 mission，ensuring the success of the world′s first robotic sampling and return mission from the far side of the Moon，valuable reference and experience are provided for follow-up lunar exploration and deep space exploration missions. Related Articles | Metrics

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Equilibrium of orbital pursuit-evasion-defense three-sided game LI Zhenyu, LIN Kunpeng, HOU Yuzhuo, LUO Yazhong Chinese Space Science and Technology    2024, 44 (4): 90-101.   DOI: 10.16708/j.cnki.1000-758X.2024.0060 Abstract （394）      PDF（pc） （7093KB）（598）       Knowledge map    To improve the defense ability of the spacecraft in orbit，an orbital pursuit-evasion-defense（PED）linear-quadratic game is investigated.Three players are called the pursuer，evader，and defender，respectively.The pursuer aims to intercept the evader，while the evader tries to escape from the pursuer，accompanied by a defender who attempts to protect the evader by intercepting the pursuer actively.Due to the existence of the defender，the pursuer has to evade the defender when chasing the evader.Meanwhile，cooperation between the evader and the defender may decrease the difficulty of escape.For such a three-sided game，a linear-quadratic differential game model is established with a performance index combining three players′ energy consumption and the distance.Then the necessary conditions for the Nash equilibrium of the three players are derived and the optimal pursuit guidance law and evasion-defense guidance law are obtained.Furthermore，the equilibrium solution is extended to a more general PED scenario with multiple defenders.Simulation results show that a defender can improve the survivability of the evader.Even with inferiority in maneuverability，they can win the pursuer cooperatively.Besides，an initial position close to the pursuer or evader is not the best choice for the defender who flies around the evader.The defender has favorable positions. 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 （944）      PDF（pc） （4467KB）（1348）       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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Multi-impulse pursuit-evasion game in GEO based on improved dung beetle optimization GUO Yanning, LI Gaojian, YU Yongbin Chinese Space Science and Technology    2024, 44 (4): 1-10.   DOI: 10.16708/j.cnki.1000-758X.2024.0052 Abstract （637）      PDF（pc） （4364KB）（582）       Knowledge map    This paper investigates the pursuit-evasion game of GEO with J2 perturbation and impulsive thrust considering perception delay.An optimization model of orbital pursuit strategy is established，considering fuel consumption，single impulse velocity increment，impulse interval time，mission duration，impulse quantity，and terminal distance.The design variables include the number of impulses，the sequence of maneuver moments，and the sequence of impulse increments.The pursuing spacecraft pursues the target spacecraft through multiple impulses.To enhance problem-solving efficiency，an improved Bernoulli dung beetle optimization algorithm（IBDBO）utilizing Bernoulli chaotic mapping and optimal value guidance is proposed.Additionally，Lambert maneuver correction is introduced to address terminal constraint satisfaction issues.The comparison experiments with other intelligent algorithms verify the superiority of this algorithm in terms of convergence speed，convergence stability and optimization efficiency.Furthermore，simulations in real scenarios with perceptual delay demonstrate the effectiveness of this algorithm for planning pursuit strategies.Finally，the causal relation between terminal distance of both sides in the game and the target spacecraft′s maneuvering capabilities，perception delay time is explored. 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 （1259）      PDF（pc） （4662KB）（3051）       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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System design of spaceborne large aperture perimeter truss antenna FENG Tao, ZAHNG Qingjun, LIN Kunyang, WANG Lipeng, ZHANG Qiao, YANG Jungang, XIAO Yong Chinese Space Science and Technology    2025, 45 (1): 24-33.   DOI: 10.16708/j.cnki.1000-758X.2025.0003 Abstract （513）      PDF（pc） （9223KB）（567）       Knowledge map    The perimeter truss antenna is the ideal structure of the spaceborne deployable antenna with very large aperture, which is the key payload for high-orbit communication and high-orbit remote sensing satellite applications. The spaceborne perimeter truss antenna is a typical prestressed structure composed of the surrounding truss and cable network system. The accuracy of surface and the fundamental frequency of antenna are the main performance indexes of antennas. On-orbit reliable deployment is the premise of on-orbit application, and reliable deployment is the most important part of antenna design. The influence of ring antenna system parameters on on-orbit performance is analyzed. Based on the analysis of the deployable power system and the transmission power system, the influence of system parameters of the ring antenna on the deployable reliability is expounded. The method of evaluating the on-orbit performance design by structural statics and the deployable reliability by dynamic means are proposed. The design flow of spaceborne large aperture perimeter truss antenna system is defined by strength verification and on-board lock-release design by structural dynamics method, and the optimization strategy of each design parameter is proposed. It provides a reference for technical research and engineering development of the larger aperture spaceborne deployable antenna in the future. Related Articles | Metrics

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Current status and prospect of multisource remote sensing data in battlefield environment intelligent situational awareness SHAO Zhenfeng, DANG Chaoya, ZHANG Hongping, WU Changzhi, QI Xiaofei, HUANG Jun Chinese Space Science and Technology    2024, 44 (1): 11-22.   DOI: 10.16708/j.cnki.1000-758X.2024.0002 Abstract （770）      PDF（pc） （4641KB）（1081）       Knowledge map     In the face of the rapid change of complex battlefield environment information，grasping the situational awareness of complex battlefield environment in a timely，comprehensive and accurate manner is the prerequisite for winning the information war in the future.In order to explore the development direction of multi-source remote sensing data in battlefield environment situational awareness，on the basis of extensive investigation of remote sensing requirements for battlefield environment situational awareness，we firstly expounded the concept and connotation of battlefield environment situational awareness，then gave an overview of multi-source remote sensing data processing and battlefield situational awareness applications.Next，we analyzed the challenges，progress and development trend of remote sensing in battlefield environment situational awareness.In general，remote sensing provides a variety of observation data for battlefield environment situational awareness，and the combination of remote sensing and artificial intelligence algorithm can provide a variety of applications for military battlefield environment situational awareness and offer data assistance to commanders for decision-making.However，there are still a lot of challenges to be solved.Based on the analysis of the current achievements and challenges，we put forward the prospect of remote sensing in the battlefield environment situational awareness，and pointed out that the interpretability of deep learning based on remote sensing and the intelligent battlefield are the difficulties to break through the development of remote sensing in the battlefield environment situational awareness. Related Articles | Metrics

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Construction and transfer of space-based spatial-temporal reference in earth-moon space ZHOU Huichao, ZHENG Jinjun, WANG Haihong, BI Shaojun Chinese Space Science and Technology    2024, 44 (3): 51-59.   DOI: 10.16708/j.cnki.1000-758X.2024.0038 Abstract （552）      PDF（pc） （6434KB）（818）       Knowledge map     Cislunar space is gradually becoming a focal area for human space exploration activities.Constructing a high-precision spatial-temporal reference and service is significant for planning and executing cislunar space missions.It is not only a systematic expansion of the spatial-temporal reference in the near-earth region，but also an important approach to enhance the guarantee capability of spatial-temporal information in cislunar space.With the development of GNSS，the infrastructure of spatial-temporal reference in the nearearth region is relatively comprehensive.The navigation system in the lunar region is similar to that of the near-earth region，and various solutions have been proposed.However，cislunar space also includes areas beyond the earth and the moon.Factors such as large airspace and particularity of dynamics should be adequately considered when the spatial-temporal reference is constructed，which can provide spatial-temporal information service with high benefits and connect the spatial-temporal reference of the earth and the moon organically.In this article，the spatial-temporal reference framework in cislunar space was designed based on the current demand of development.With characteristics of cislunar space beyond the earth and the moon considered，the scheme for constructing，tracing and transferring of the space-based earth-moon libration point spatial-temporal reference was researched and proposed.This scheme is anticipated to deliver a spatial-temporal information service with high accuracy and benefits，offering valuable reference for integrative construction and development of spatial-temporal reference in cislunar space. Related Articles | Metrics

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Research on lunar base based on cave LI Linling, LIU Jingang, HOU Yukui, LIU Wei, LI Mingfu, YIN Shuohui, WANG Lei, XU Mengchuan, Peng Jing, SUN Zezhou Chinese Space Science and Technology    2025, 45 (3): 9-18.   DOI: 10.16708/j.cnki.1000.758X.2025.0034 Abstract （582）      PDF（pc） （7961KB）（532）       Knowledge map    The relevant policies， plans and specific projects of cave lunar bases at home and abroad were investigated systematically， with a focus on the comparative analysis of the existing gaps in research achievements. Based on the image information of lunar exploration at home and abroad and the research results of cave lunar base concept， the feasibility concept of cave lunar construction has been sorted out. Based on the unique advantages of the cave (such as suitable temperature， low radiation， less lunar dust， etc.) and the objective conditions of the difficulty of building a lunar base， a qualitative analysis was conducted on various concepts of cavebased lunar bases. Each type of lunar base configuration shows unique advantages： the cavebased lunar base based on the transformation of craters makes full use of the natural terrain on the lunar surface， combines the natural structural characteristics and artificial transformation requirements， and has significant advantages insitu resource utilization. Whether it is an unmanned or manned cave lunar base， it will go through four key strategic stages： lunar exploration， lunar address selection， lunar base construction and lunar base application. Although a large number of lunar images have been obtained through the launched lunar orbit probe， lunar surface probe and other exploration means， the current lunar surface exploration capabilities still need to be further improved to provide stronger support for the "site selection" work of the construction of the cave lunar base. At the same time， it is urgent to accelerate the development of key equipment for the construction of lunar bases as soon as possible， provide implementation tools for the construction of unmanned lunar bases， implement the "foundation" task of the cave lunar base， and realize the strategic goal of "cave utilization" of the cave lunar base as soon as possible. Related Articles | Metrics

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Chang′e-6 mission planning leveraging geometry approach MENG Zhanfeng, GAO Shan, ZHAO Qiao, ZHANG Xiangyu Chinese Space Science and Technology    2024, 44 (6): 1-15.   DOI: 10.16708/j.cnki.1000-758X.2024.0086 Abstract （604）      PDF（pc） （15016KB）（523）       Knowledge map    The Chang′e-6 mission is the first lunar far-side sampling return mission in the world. The mission planning is an important assignment in the spacecraft system design. Mission planning problem is conventionally converted to the numerical constraints optimization problem in the traditional method. However, by using this method, the constraints could not be satisfied directly, and at the same time, the design variables dimension increased, the computing efficiency decreased, and the physical meaning was not apparent. A new mission planning approach using the mission geometry is proposed in this paper. According to the new approach, the periapsis constraints of the Earth-to-Moon and Moon-to-Earth transfer trajectories, the relative geometry constraints on sampling point and lunar orbit plane, and the geometry relationship of the Sun-Earth-Moon are fully considered. The new approach reduced the design variables dimension, improved the computing efficiency. In addition, it also has the advantage of intuitive spatial geometric interpretation, and the result can be verified easily. The new approach has been applied to mission planning and trajectory design in the Chang′e-5 and Chang′e-6 missions successfully, and will be adopted in the future lunar exploration mission. Related Articles | Metrics

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Research on ultra-wideband high power amplifier technology LI Donglin, YANG Fei Chinese Space Science and Technology    2024, 44 (4): 153-160.   DOI: 10.16708/j.cnki.1000-758X.2024.0066 Abstract （292）      PDF（pc） （8420KB）（483）       Knowledge map    Ultra-wideband power amplifier is the core，versatile and high value-added components in wideband communications，electronic countermeasures and radar systems.As the demand for communication systems continues to increase，the need for power amplifiers with wider bandwidth，higher efficiency，and more power is imminent.An ultra-wideband power amplifier is designed based on GaN（gallium nitride）high electron mobility transistor（HEMT）with operating frequency from 0.46GHz to 3.9GHz.Firstly，the input matching is optimized to achieve absolute stability and high gain in the full frequency band.Secondly，the high power and high efficiency output matching impedance space is extracted by load-pull design at different frequency points within the target frequency band，and then a four-stage Chebyshev impedance converter is applied as the output matching topology to achieve high efficiency and high output power in the wide frequency band.The test results show that within the operating band from 0.46GHz to 3.9GHz，the overall output power（Pout）is greater than 13.8W with the maximum output power of 24.1W；the full-band drain efficiency is greater than 50.1% with the maximum value of 67.2% at 1.5GHz.The measured results are in good agreement with the simulation results，and the design idea is intuitive and clear，which provides a direction for designing the currently required ultra-wideband power amplifier.  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 （906）      PDF（pc） （1709KB）（1238）       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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System architectures and key technologies of lunar surface communication and navigation infrastructure LI Jionghui, WANG Zijie, BAI Fan, GU Zheng, XIN Pengfei, JIA Min, ZHAO Hongbo, PENG Jing Chinese Space Science and Technology    2024, 44 (3): 30-42.   DOI: 10.16708/j.cnki.1000-758X.2024.0036 Abstract （554）      PDF（pc） （6199KB）（723）       Knowledge map    As a significant component of the cislunar space infrastructure（CSI），lunar surface communication and navigation infrastructure（LSCNI） provides more convenient communication networking services for the surface local users within hotspot areas，and also provides reference of surface local positioning and navigation as well as certain positioning，navigation and timing（PNT） capacities.On the basis of trend analysis，overall architectures of lunar surface communication and navigation infrastructure are proposed focusing on the medium and long-term strategic development of current major projects as well as future large-scale lunar activities.The architectures contain the network architecture and the lunar surface-space interfaces.Then，the solutions to some core issues such as lunar frequency planning，radio wave channel modeling，network access，high-speed transmissions，positioning and navigation methods are analyzed.Finally，suggestions for phased construction and technological development roadmap are proposed，providing reference for the planning and construction of communication and navigation systems for future lunar exploration missions. Related Articles | Metrics