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25 April 2019, Volume 39 Issue 2 Previous Issue    Next Issue

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Onorbit intelligent identification of combined spacecraft′s inertia parameter based on deep learning JIN Chendi, KANG Guohua, GUO Yujie, QIAO Siyuan 2019, 39 (2):  1-12.  doi: 10.16708/j.cnki.1000-758X.2019.0003 Abstract ( 941 )   PDF (8791KB) ( 726 )   Save Aiming at the problem of unknown dynamic parameters of the new assembly during the onorbit service, a parameter identification algorithm based on convolution neural network was proposed with the help of deep learning in multiparameter optimization. The algorithm realizes the identification of the combined spacecraft′s multiparameter under the condition of external force and non conservation of linear momentum and angular momentum. A 4layer convolution neural networks was designed by using the characteristic of the weight sharing of the convolution neural network. The identification of inertial parameters with high precision was achieved by plenty of training of state data in a specific form of storage in a short time. The feasibility of the convolution neural network algorithm was proved by simulation calculation. The results show that the proposed method can accurately and quickly identify the mass, centroid position and inertia matrix of combined spacecraft under the influence of external random force and moment, the identification accuracy is within 3%. Related Articles | Metrics

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Exprimental study on thermal conductivity enhancement technique for space carbonfiber shell structure PANG Le, SUN Jingwen, ZHAO Kaixuan, DAI Shanliang, LIU Gang, PENG Cong 2019, 39 (2):  13-18.  doi: 10.16708/j.cnki.1000-758X.2019.0004 Abstract ( 662 )   PDF (4452KB) ( 750 )   Save In order to improve the thermal conductivity of space Carbon Fiber Reinforced Plastics (CFRP) shell structure, three techniques of enhancing thermal conductivity were designed, and vacuumthermal test was performed on the specimens which were treated according to these techniques, control group was prepared as well. These techniques include bonding high thermal conductivity film materials on the specimens’ surface and cladding multi layer insulation with high thermal conductivity film interlayers. According to test results, the technique of bonding carboncarbon composites film has an obvious advantage over the other two, increasing the thermal conductivity of CFRP shell structure by seven times. If this technique is used in conjunction with multi layer insulation cladded with high thermal conductivity film interlayer, better results can be achieved. Related Articles | Metrics

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Spacecraft attitude measurement based on samebeam interferometry ZHANG Tiangang，REN Tianpeng，XIE Jianfeng，LU Weitao，YIN Feifei 2019, 39 (2):  19-26.  doi: 10.16708/j.cnki.1000-758X.2019.0008 Abstract ( 635 )   PDF (6350KB) ( 509 )   Save A samebeam interferometry based mathematical model of spacecraft attitude was established, and a solution method was proposed. The solvability of the model and the precision factor were analyzed. Numerical simulations of spacecraft attitude determination based on samebeam interferometry were carried out, where an onorbit spacecraft was simulated, and the relationship between calculation error and observation pitch angle were analyzed and verified. The results show that the effective spacecraft attitude can be obtained by using three ground stations to carry out the samebeam interferometry for three downlink antenna signals with a constraint of precision factor，and the highest accuracy achieved is 0.001° . The method proposed can be used as an attitude measurement backup for onorbit spacecraft. Related Articles | Metrics

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Behavior models of passive intermodulation interference in passive devices WU Jiayi，HU Tiancun，LIANG Bizheng，ZHANG Xuqi，LIU Celun 2019, 39 (2):  27-33.  doi: 10.16708/j.cnki.1000-758X.2019.0009 Abstract ( 820 )   PDF (1659KB) ( 636 )   Save Passive intermodulation often affects the normal operation of multicarrier communication satellites. Because of the complexity of passive intermodulation interference, it is impossible to analyze the passive intermodulation component directly. Therefore, it is necessary to establish models. According to the frequency distribution characteristics of passive intermodulation interference, double exponential function model and Volterrra series model were adopted to fit passive intermodulation interference, and the time series model of passive intermodulation interference of QPSK signals was established. By performing MATLAB simulation, the results show that the peak values appear at the theoretical frequency points. The ratio of the amplitude value at the center frequency of the input signals to the amplitude value at the passive intermodulation frequency components accords with the theoretical analysis. Related Articles | Metrics

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Study on interferometric imaging based on photonic integrated circuits YU Gongmin，XIAO Aiqun，JIN Libing，TONG Xiliang，ZHOU Feng 2019, 39 (2):  34-40.  doi: 10.16708/j.cnki.1000-758X.2019.0010 Abstract ( 707 )   PDF (1944KB) ( 707 )   Save The Segmented Planar Imaging Detector for Electrooptical Reconnaissance(SPIDER) system is an interferometric imaging system based on photonic integrated circuits. It is one of the effective means to improve the resolution of remote sensing imaging, decrease the difficulty of system processing, and reduce the size, weight and power. The current research status of SPIDER is reported. The basic principle and composition was also studied. An imaging model was established based on partially coherent light theory. The method of interference fringe detection is studied based on balanced four quadrature detectors. The index system of imaging system was also analyzed.Finally, the SPIDER imaging capability was simulated and verified. Based on the results of simulation, the imaging ability of SPIDER can broaden its application in remote sensing reconnaissance, spatial situation awareness and other fields. Related Articles | Metrics

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Lunar surface sampling point selection for uneven terrain ZHENG Yanhong, YAO Meng, JIN Shengyi, ZHAO Zhihui, DENG Xiangjin ,HE Xiaoyang 2019, 39 (2):  41-48.  doi: 10.16708/j.cnki.1000-758X.2019.0006 Abstract ( 575 )   PDF (13989KB) ( 545 )   Save Surface sampling,applied in situ exploration and sample return mission at this stage,is an important method of acquiring extraterrestrial body characteristics. For big sampler, some constraints are introduced into lunar surface sampling process under uneven terrain. The influences of uneven terrain were analyzed, considering a class of big scaled sampler. The sufficient condition of adoptable surface sampling was proposed, and the establishing method of adoptable point which contains visual subarea division, subarea extension, local average normal vector sparse and base point sphere detection was constructed. Numerical simulations demonstrate the effectiveness of the establishing approach, and the speediness of subarea and parallel computing. Related Articles | Metrics

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Online design of optimal carrier tracking loop bandwidth for tightlycoupled GPS/INS XU Xiaohan, WANG Kedong 2019, 39 (2):  49-57.  doi: 10.16708/j.cnki.1000-758X.2019.0005 Abstract ( 556 )   PDF (4788KB) ( 410 )   Save In GPS(Global Positioning System)/INS(Inertial Navigation System) ultratight coupling system, the tracking performance of satellite signal depends directly on the bandwidth of carrier tracking loop. In order to improve the computation accuracy of optimal bandwidth, on the basis of analyzing the tracking characteristics of INSassisted PLL(Phase Locked Loop), the deduction of the assisting error of carrier Doppler shift and its rate of change was performed, and the loop tracking error model aided by INS was established. With the realtime estimation of tracking carriertonoise ratio, the discrete secondorder Newtonian iterative method was applied, and the optimal bandwidth was calculated and adjusted in real time. The simulation results show that the optimal bandwidth iterative method achieves 99.6% accuracy in 11 iterations. When the optimal bandwidth is used as the real time bandwidth of the loop, the tracking accuracy of the loop can be effectively improved under the condition of weak signal and low assisting information accuracy. Related Articles | Metrics

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Orbit control force coefficient identification by Charp recursion method ZHANG Ying，WANG Xijing，YUAN Bo，KONG Dalin，BIAN Yanshan 2019, 39 (2):  58-64.  doi: 10.16708/j.cnki.1000-758X.2019.0011 Abstract ( 728 )   PDF (1063KB) ( 371 )   Save Spacecraft orbit maneuvers are required in spacecraft orbit capture, orbit maintenance and obstacle avoidance. Considering the fact that during spacecraft orbital maneuver, the thrust coefficient is the binding constant, error can be great due to the unoptimized parameter. The fitting coefficient of the control force is identified as a correction control parameter to compensate for the orbital control error, so as to improve the accuracy of orbit control. The historical orbit control data of typical spacecraft platform and its engine were analyzed in a statistical way. By analyzing the previous orbit control theory and inorbit control data, the orbit control empirical model was established. With the input and output of the current measurable system, the future evolution of system output was predictable and the empirical formula of the relationship between the error of actual orbit control and the control parameters under different working conditions was concluded.Two types of Low Earth Orbit (LEO) satellites with semimajor axis variation above and below 300 meters were selected to analyze historical data of orbital control. After the actual data test, the accuracy of the velocity variation forecast after the thrust coefficient fitting by the Charp recursion method is higher. This kind of calculation method makes use of historical data of orbit control, and the calculation method is simple, which improves the prediction precision of orbit control speed increment and has reference significance for the implementation of orbit control. Related Articles | Metrics

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Reorganization design of taskoriented space information networks architecture YU Shaobo, WU Lingda, CHEN Xiaoyan, LI Chao, YAO Zhonghua 2019, 39 (2):  65-72.  doi: 10.16708/j.cnki.1000-758X.2019.0012 Abstract ( 604 )   PDF (4468KB) ( 750 )   Save For the design of Space Information Networks (SINs) architecture and the multiplicity and multidimension problems of its mission task, a reconfigurable design method of SINs architecture was proposed. Firstly, the development of SINs and its architecture at home and abroad were introduced, and the requirement of reorganization design of SINs architecture was analyzed. Secondly, based on the concept, structure and characteristics of SINs, some reorganization design principles including loose coupling, compatibility, isolation and deconstruction were established. Meanwhile, the connotations of the Reorganization Management Center (RMC) and the Reorganization Resource Center (RRC) were defined, and the operating mechanism of RMC and RRC was analyzed. A formalized reorganization network architecture model based on 5 dimensions of target, topology, entity, data and scheme was proposed, and the realization algorithm flow of reorganization network architecture was given. Finally,a case study of the architecture reorganization design with an example of an antimissile operation was carried out, and a simulation demonstration of reorganization network on the STK platform was realized. The application of reorganization design in practice was demonstrated and verified, achieving the desired goal. Related Articles | Metrics

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A hyperspectral remote sensing image classification method based on multispatial information LIU Yongmei，MA Xiao，MEN Chaoguang 2019, 39 (2):  73-81.  doi: 10.16708/j.cnki.1000-758X.2019.0013 Abstract ( 544 )   PDF (2299KB) ( 668 )   Save In the field of hyperspectral remote sensing image classification, spatial and spectral feature fusion can improve the effect of classification. A multifeature spectral and spatial classification method for hyperspectral images was proposed. In the postprocessing procedure, the saltandpepper noises were removed by using superpixel information. It was also used in the preprocessing procedure, and the feature vector of pixels was weighted by superpixel information. The experiment results show that the results of proposed method are better than the present methods. Related Articles | Metrics

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Point precise positioning for LEO satellite based on realtime SSR data KANG Guohua，LIU Yao，QIAO Siyuan，JIN Chendi，GUO Yujie，LIANG Ertao 2019, 39 (2):  82-89.  doi: 10.16708/j.cnki.1000-758X.2019.0007 Abstract ( 972 )   PDF (2968KB) ( 761 )   Save The method of realtime positioning for LEO satellites was studied. GPS positioning is usually used in the realtime positioning of low orbit satellites. Due to the use of broadcast ephemeris parameters and ordinary crystal vibration, the precision is generally within 10m, which cannot meet the needs of highprecision realtime positioning. IGS organization generates the precise ephemeris and clock error products through the global GPS tracking analysis centers, and releases the SSR ephemeris and clock error correction products on the Internet. These IGS products were investigated,and it was put forward that under the condition of existing observing and controlling support, highprecision location of SSR could be achieved by highdensity injection of information flow. The background of augmentation load for a low orbit micro satellite was applied. The ephemeris and clock difference of a dual frequency GPS receiver were corrected with 1057 and 1058 data in IGS03 products, using the recursive least square estimation and LAMDA fuzziness to deal with the carrier phase and pseudo distance information. Related Articles | Metrics