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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 （1059）      PDF（pc） （3043KB）（1754）       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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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 （851）      PDF（pc） （4662KB）（2158）       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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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 （246）      PDF（pc） （4641KB）（252）       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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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 （430）      PDF（pc） （4467KB）（554）       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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Design and analysis of radiating rib space deployable antenna mechanism TIAN Dake, SONG Yuqun, JIN Lu, GAO Haiming, LIU Rongqiang, ZHAO Bingfeng Chinese Space Science and Technology    2024, 44 (2): 40-50.   DOI: 10.16708/j.cnki.1000-758X.2024.0020 Abstract （53）      PDF（pc） （9457KB）（104）       Knowledge map    The deployable antenna mechanism is a key component of the mesh deployable antenna，which has a significant influence on the stability and stiffness of the structure after deployment.A new configuration of radiating rib space deployable antenna mechanism was designed to address the development trend of large scale，high storage rate，and high accuracy of space deployable antennas.Firstly，the overall structural design of the antenna was designed，and a three-dimensional model of the structure was established based on the dimensional calculation of the structural composition.Then，the kinematic simulation study of the mechanism was carried out by using numerical simulation software，and the variation law of the motion was analyzed.Finally，a finite element model was established，and the structural modal analysis was carried out.The results show that the proposed mechanism can realize the motion change from folded state to deployed state，and that the mechanism has good synchronization during the deployment process without interference between the components，which verifies the correctness and feasibility of the structural scheme and principle.The research results can provide a reference for research on the basic theory of a deployable antenna mechanism and related engineering applications. 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 （618）      PDF（pc） （1102KB）（1454）       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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Recent progress and prospect of hightemperature heat pipes technology LI Jin-Wang, DAI Shu-Gang null    2019, 39 (3): 30-.   DOI: 10.16708/j.cnki.1000-758X.2019.0018 Abstract （1036）      PDF（pc） （1715KB）（1732）       Knowledge map    Hightemperature heat pipes have a good heat transfer performance and can be used for high working temperature. They have an expansive application prospect in the field of thermal protection system of hypersonic vehicle, cooling of space reactor and utilization of solar energy, and so on. The recent progress of hightemperature heat pipes is reported,including the startup characteristic from the frozen state and heat transfer performance of hightemperature heat pipes, the experimental studies, the numerical analysis studies. The effects of the inclination angles, the working fluid parameters, the fill charge ratio, the noncondensable gas, the material, the structure and the sizes on the startup characteristic from the frozen state and heat transfer performance of hightemperature heat pipes are presented.The applications of hightemperature heat pipes for thermal management of hypersonic flight vehicles, cooling of space reactor and utilization of solar energy are summarized. The future development direction is also pointed out, such as the numerical analysis model and engineering application of hightemperature heat pipes. The future research suggestions of hightemperature heat pipes are also put forward. Related Articles | Metrics

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GEO satellite communication link budgets calculation and analysis XU Ting, LAN Hai, ZHANG Hongjiang Chinese Space Science and Technology    2020, 40 (3): 83-92.   DOI: 10.16708/j.cnki.1000-758X.2020.0035 Accepted: 20 January 2020 Abstract （1096）      PDF（pc） （3338KB）（1968）       Knowledge map    As an important technology, satellite-ground link budget calculation is the theoretical basis of satellite communication system designing which directly decides the link availability. As there are many factors which may affect the satellite link, any unreasonable factor in the design would make the whole satelliteground link unavailable and leads to a big loss. Moreover, there is no ideal satellite link situation unless overlooking some factors, which is also a difficulty during the link budget calculation. Based on the international common calculating method, GEO satellite link was analyzed thoroughly, separating the whole link into uplink and downlink. Then a practical example was analyzed and calculated according to the project experience in LAOSAT Company. At last, different reasonable designing methods in terms of different link configurations were obtained, which could be the references to link calculation and analysis of GEO satellite communication. 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 （385）      PDF（pc） （3765KB）（790）       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

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A review for space-based ADS-B NI Jiushun, CHEN Lihu, YU Sunquan, LI Songting, GUO Jianming, LUO Aobo, LI Jinhua Chinese Space Science and Technology    2022, 42 (1): 30-37.   DOI: 10.16708/j.cnki.1000-758X.2022.0003 Abstract （278）      PDF（pc） （4911KB）（813）       Knowledge map    As an important technology of air traffic control in the future, space-based ADS-B technology can overcome the difficulties of ground equipment deployment in desert, ocean, polar and other places. The space-based ADS-B technology has the characteristics of a wide range of reconnaissance and reception, which can cover the whole world, and relevant studies have been carried out in many countries. According to the frontier characteristics of ADS-B technology, the research progress of ADS-B technology is investigated. First of all, the principle and related research of ADS-B are summarized. Secondly, the key technologies of ADS-B reception on board are reviewed from four aspects: antenna technology, radio frequency circuit technology, signal processing and constellation design method. Finally, the application of ADS-B data and its future development prospect are described. Related Articles | Metrics

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Vibration suppression of cable net antenna based on repetitive active disturbance rejection control DONG Yutong, WANG Wenhao, MA Xiaofei, LIU Lei Chinese Space Science and Technology    2023, 43 (1): 109-118.   DOI: 10.16708/j.cnki.1000-758X.2023.0011 Abstract （137）      PDF（pc） （7003KB）（173）       Knowledge map    In order to solve the problem of vibration suppression of cable net space antenna，an active vibration control method based on active disturbance rejection repetitive compound controller was proposed.At first，the vibration dynamic model of antenna surface was established by using finite element method.The model order was reduced based on modal truncation method.Then，based on the energy minimization criterion，the position of sensor/actuator was optimized by using genetic algorithm.Finally，the active suppression algorithm of antenna surface vibration based on linear active disturbance rejection control was designed，and the feedforward repetitive control algorithm was designed to improve the ability of the controller to suppress periodic disturbance by learning the periodic error of feedback control.The simulation results show that the proposed control method can reduce the profile disturbance by 97.0%，and the control effect is better than PID controller.The designed control method provides a new technical approach for the vibration control of antenna mesh surface. Related Articles | Metrics

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3D printing densification of lunar regolith simulant LIU Yiwei, ZHANG Xian, WANG Chao, SONG Jian, CHEN Xiong, Yao Wei Chinese Space Science and Technology    2023, 43 (6): 66-73.   DOI: 10.16708/j.cnki.1000-758X.2023.0085 Abstract （179）      PDF（pc） （7898KB）（405）       Knowledge map    The insitu 3D printing of lunar regolith（additive manufacturing）can realize the in-situ construction of the lunar base and the insitu manufacturing of key components，and can greatly reduce the cost and risk of the lunar exploration mission.A selective laser melting lunar regolith simulant experiment system was built to carry out single-track molding experiments to explore the effect of the first powder layer thickness on the densification of the sample，while the width and depth of each track were measured.The results show that the width of the single-track decreases with increasing scanning speed until the width is almost constant.At the same laser power，the single-track depth becomes deeper as the first powder layer thickness increases.The singletrack depth increases and then decreases with the increase in scanning speed.The density of a single-track can reach 2.5g/cm3，and the relative density is 86%.As the scanning speed increases，the density of single-track for different layer thicknesses is stabilized at 1.7g/cm3.When the first layer of powder is thinner，the density of single-track is also slightly higher than other layer thicknesses. Related Articles | Metrics

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Structure design of deployable panels based on inflatable film ZHANG Yuanxun, XU Liping, ZHANG Xiaomin, HUANG Gao Chinese Space Science and Technology    2024, 44 (2): 30-39.   DOI: 10.16708/j.cnki.1000-758X.2024.0019 Abstract （60）      PDF（pc） （11979KB）（52）       Knowledge map    The deployable membrane structure has the advantages of light weight and high storage ratio.Through theoretical analysis and experimental verification，the mapping relationship between bending moment and internal pressure，radius and expansion degree of inflatable film tube was obtained.Furthermore，the thick plate problem of the two-stage deployable panels was solved with the method of "thick edge wrapping".The rotational lock，rotational slip lock and lap lock connection structures were designed.Three kinds of large-scale deployable panels structures，namely two-stage deployable rectangular panels，circular panels and shutter-shaped rectangular panels，were proposed，and the modal simulation of the deployable state was carried out to compare the modal shapes.This paper can provide a reference for large scale inflatable structure. Related Articles | Metrics

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Study on discharge life characteristics of micro-cathode arc thruster WANG Wenqian, LIU Xiangyang, WANG Shuai, CHEN Shichang, ZHAO Zijing, GENG Jinyue, SHEN Yan, WANG Ningfei Chinese Space Science and Technology    2021, 41 (3): 24-30.   DOI: 10.16708/j.cnki.1000.758X.2021.0034 Abstract （328）      PDF（pc） （8055KB）（304）       Knowledge map    Microcathode arc thruster (μCAT) has a good application prospect in micronano satellite space missions, but the life span is an important factor restricting its development at present. An automatic data acquisition system was developed, and the whole life tests at different discharge frequencies were carried out. The morphology changes of cathode materials and conductive films after failure were observed and analyzed. The results show that, at the initial stage of the thruster, the discharge characteristic is an unstable stage, which accounts for less than 10% of the whole life of μCAT. The discharge of thin film resistance is relatively stable in the early stage, which is of the order of several hundred euros, and increases rapidly to the order of thousands of euros when it is close to failure, and the peak current decreases sharply until failure. The increase of discharge frequency makes the heat accumulation in the cathode pit area, enhances the breakage of the conductive film, leads to the early failure of the thruster and reduces the life of the thruster. The uneven distribution of arc ablation position leads to the decrease of cathode utilization, which is an important factor restricting the life of μCAT. Related Articles | Metrics

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Study on moment dumpling of electric propulsion satellite MA Xue, HAN Dong, TANG Liang null    2016, 36 (1): 70-76.   DOI: 10.3780/j.issn.1000-758X.2016.0013 Abstract （1169）      PDF（pc） （3521KB）（1433）       Knowledge map    Moment dumpling of electric propulsion satellite can be established by pointing the thrust vectors slightly away from the center of mass. On the basis of this method, electric propulsion moment dumpling for both normal mode and failure mode was investigated. The analytic solution of optimal dumpling directions was given,and the question that whether the control arc should be considered was discussed. The simulation results show that proposed method can effectively perform the moment dumpling by electric thrusters. Related Articles | Metrics

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Research on real-time precise point positioning with iGMAS ultra-fast ephemeris#br# XU Weizheng, KANG Guohua, PENG Pan, ZHOU Hongtao, LIU Zongqiang, ZHAO Teng Chinese Space Science and Technology    2021, 41 (1): 29-37.   DOI: 10.16708/j.cnki.1000-758X.2021.0004 Abstract （322）      PDF（pc） （8161KB）（163）       Knowledge map    The China-led International GNSS Monitoring & Assessment System (iGMAS) differs from the IGS system (international GNSS service, IGS) in product accuracy. Real-time precise point positioning(PPP) applications are mostly based on IGS real-time and near real-time products. To improve this situation, we aimed at iGMAS product characteristics and the demand for ultra-fast products with real-time PPP, evaluated the accuracy and stability of iGMAS ultrafast ephemeris, designed an iGMAS product real-time/post-event download application, and carried out real-time precise point positioning research based on iGMAS ultra-fast ephemeris through combining with NovAtel OEM617 dual-frequency receiver. The experimental results show that the positioning error can converge to the decimeter level after 23 minutes, which is an order of magnitude higher than the original positioning accuracy of the receiver and has good stability. The root mean square error of the positioning error in the E/N/U direction is 7.2cm, 6.4cm, 15.2cm, similar to IGS ultra-fast ephemeris in real-time PPP experiment. This study implements a complete solution for iGMAS data acquisition, evaluation, and real-time PPP applications, verifies performance of iGMAS ultra-fast products and provides reference for the application of iGMAS products. 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 （33）      PDF（pc） （6075KB）（49）       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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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 （702）      PDF（pc） （1709KB）（623）       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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Configuration design and optimization of deployable membrane sunshield for spacecraft PENG Tao, LIN Qiuhong, LI Bingyan, QIU Hui, LIU Rongqiang, LUO Ani Chinese Space Science and Technology    2023, 43 (1): 129-138.   DOI: 10.16708/j.cnki.1000-758X.2023.0013 Abstract （136）      PDF（pc） （7453KB）（189）       Knowledge map    In response to the current demand for lightweight spacecraft sunshield,a flexible flat membrane sunshield was designed based on the mass and the effective area ratio on the premise that the effective area of the membrane sunshield remains unchanged.In order to improve the edge stress of the membrane while avoiding the reduction of the effective circle area,the edge of the membrane sunshield was optimized for arc design.The results show that when the thin-membrane sunshield is a regular hexagon,the symmetry of the structure can be ensured,and the minimum mass corresponding to the percentage of unit effective area can be obtained.The stress distribution model of the membrane sunshield was established with the stress superposition method,and the theoretical calculation value of the membrane edge stress was obtained.The influence of the increase of arc edge arch height on the membrane edge stress and the effective circle area ratio was explored.When the two function curves intersect at a point,the optimal arch height of the membrane arc edge can be selected.According to the designed parameters of the thin membrane sunshield,a test prototype of the thin membrane sunshield was built and the tensile experiment was performed.The edge tension of the membrane is high,which proves that the arc edge design plays an important role in improving the stress and stiffness of the membrane. Related Articles | Metrics

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Radiometric Calibration and Accuracy Analysis based on Spaceborne SAR TAO Man-Yi, JI Peng, HUANG Yuan-Bao, JIANG Yan null    2015, 35 (5): 64-70.   DOI: 10.3780/j.issn.1000-758X.2015.05.009 Abstract （944）      PDF（pc） （3082KB）（924）       Knowledge map    With the development of spaceborne synthetic aperture radar(SAR)application,the radiometric calibration technology was used to observe objects′ physical characters.    Because the radiometric calibration technology is very complex,on the study of radiometric calibration and accuracy analysis will be mostly focused in the strip mode with single channel and single polarization.Firstly,the radar equation was derivated,then with the measured calibration constant,the short-term and long-term relative calibrations were studied based on an error model and formula. At the same time,the influence of calibration constant for absolute radiometric precision was analyzed and the system correct was finished.Finally the validated result on TerraSAR-X satellite shows that the difference of the calculated value and the measured one is less than 0.05dB. Related Articles | Metrics