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25 February 2003, Volume 23 Issue 01 Previous Issue    Next Issue

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Processing Remote Sensing Image of CCD Camera With Smoothness Constraint Restoration Liu Qin Chen Shiping Ma Wenpo (Beijing Institute of Space Mechanics & Electricity, Beijing 100076) 2003, 23 (01):  .  Abstract ( 1805 )   Save The smoothness constraint method of image restoration in frequency domain and it s practical application in the remote sensing field are emphasized. The theory b ased on smoothness constraint restoration is introduced, then the remote sensing image of CCD camera with the method is processed. The curve fitting and the mat rix construction of remote sensor's system MTF are discussed and it also exp lains how the parameters of the restoration formula are choosed. Results show th at under certain conditions, the whole system MTF can be effectually improved by smoothness constraint restoration, consequently, the remote sensing image b ecomes clear. Related Articles | Metrics

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Experimental Research on the Heat Transfer Between the Solid Interfaces at Low Temperatures and Vacuum Zhao Lanping(Tongji University, Shanghai 200092) Xu Lie(Shanghai Jiao Tong University, Shanghai 200030) 2003, 23 (01):  .  Abstract ( 1674 )   Save An experimental program which investigate the thermal contact conductance (TCC) of stainless steel and aluminum alloy surface in cryogenic environment is descri bed. The effects of contact pressure (P), interface temperature and fractal para meters on TCC are emphasized. From the experimental results, it is indicated tha t the TCC P pressure exponent of this paper are all within the range of 0 4 to 0 6, and the interface temperature influences TCC through the material propert ies. As the fractal dimensions rising, the TCC increases in the condition of thi s research. Related Articles | Metrics

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Application of Grey Prediction Method for Export Power Forecast of Satellite Solar Battery Array Gu Jihai Jiang Xingwei Fan Xianfeng Song Lihui (Harbin Institute of Technology, Harbin 150001) 2003, 23 (01):  .  Abstract ( 1731 )   Save The modeling method of GM(1,1) grey model is studied. A GM(1,1)prediction model of batteries array export power is founded. Based real time method is gived acc ording to the fluctuate character of batter matrix export power. The dynamic inn ovation forecast model of GM(1,1) is founded. The forecast precision is improved greatly through the example, and the feature of batter array export power can be forecast exactly. Related Articles | Metrics

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Region of Interesting Image Coding Based on Set Partitioning in Hierarchical Trees Guo Wu Mei Li Luo Jianshu (National University of Defense Technology, Changsha 410073) 2003, 23 (01):  .  Abstract ( 1556 )   Save Region of Interest (ROI)coding is one of the innovativ e functionalities supported by JPEG2000, ROI coding is incorporated functionality into SPIHT coding with integer wavelet transform. By placing a higher emphasis o n the transform coefficients pertaining to ROI, ROI is coded with higher fidelit y than the rest of the image (BG) in earlier stages of progressive reconstructio n, thus the "important" part of the image is reconstructed more quickly than BG. This method significantly saves transmission time and storage space by terminat ing encoding or transmission in situations where ROI needs to be coded losslessl y and BG visually losslessly (lossy). Related Articles | Metrics

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Fault-Tolerant Kalman Filter for Attitude Parameters of the Spin Stabilized Satellite Hu Shaolin Huang Liusheng (University of Science & Technology of China, Hefei 230027) 2003, 23 (01):  .  Abstract ( 1651 )   Save The Kalman filter is an unbiased and linear filter of s tate vectors of the dynamical measurement system, which has simple recursive al gorithms and widely usage in the field of spacecraft control. Much attention is paid to practical approaches and some detailed cases of Kalman filter, and a new kind of fault tolerant filtering algorithm is built to estimate the attitude p arameters of the spin stabilized satellite and the system errors of measurement data. The strating values of recursive filters and estimators of covariance of errors are deduced and some valuable suggestions are given. Related Articles | Metrics

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Solving Optimal Rendezvous Using Two Impulses Based on Genetic Algorithms Wang Hua Tang Guojin (College of Aerospace and Material Engineering, National Univ. of Defense Technology, Changsha 410073) 2003, 23 (01):  .  Abstract ( 1576 )   Save Considering the influence of the first impulse's position, the model of rendezvo us between two spacecrafts using two impulses is derived. Based on that, optimal rendezvous object considering of fuel and time is constructed, and GA (Genetic Algorithms) is designed. Simulation results show that the value of performance index, considering the influence of the first impulse's position, is better than that if not considering, and prove the design fo GA is successful. Related Articles | Metrics

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The Achievements and Propects of Chinese Spacecraft Engineering Xu Fuxiang (Chinese Academy of Space Technology, Beijing 100081) 2003, 23 (01):  .  Abstract ( 1774 )   Save Over the past more than 40 years, the Chinese spacecraft engineering has gone through technical preparation phase, technological experiment phase, and engineering phase. Various satellite series have been formed such as "recoverable remote sensing satellite", "telecommunication and broadcast satellite", "meteorological satellite" and "scientific exploration and technological experiment satellite". Other two satellite series, "earth resource satellite" and "navigation and positioning satellite" will also come into being very soon. Until now China has launched 51 earth satellites and launched 4 experimental manned spacecrafts successfully. The great achievements China has obtained attract world wide attention and make big contribution to the development of national economy, national defence, cultural education and science research. With the advent of 21st centure, according to the development objective of the Chinese space technology both in short term and long term, Chinese spacecraft engineering will win even more brilliant achievements. Related Articles | Metrics

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Adaptive Backstepping Control Based Autopilot Design for Reentry Vehicle Lian Baohua Cui Hutao Cui Pingyuan (Harbin Institute of Technology Deep Space Exploration Research Center, H arbin 150001) 2003, 23 (01):  .  Abstract ( 1967 )   Save The traditional method of autopilot design is piecewise linearization based gain scheduling approach. Recently, Variant control strategies based on feedback lin earization have been widely studied. In this paper, a new kind of control strate gy for design of autopilot with nonlinear feedback based on backstepping techniq ue is presented. According to this method, the input uncertainties are taken int o account by involving both nonlinear optimization to guarantee the accuracy of the mapping from actuator to moment and adaptive term to compensate the moment's bias. Finally, the autopilot of reentry vehicle is designed with this method. The simulation results show that the method of adaptive backstepping proposed in this paper is efficient. The design process is simpler than others and easy for implement. Related Articles | Metrics

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Generalized Method of Formation Flying Configuration Design Zeng Guoqiang Zhang Yulin (Institute of Command and Technology, Beijing 101416) 2003, 23 (01):  .  Abstract ( 1693 )   Save At first, based on kinematic relationship, motion equations of surrounding satel lite with respect to reference satellite is deduced under proper assumption. Then, specific formulas of generalized method of microsatellite formation flyin g configuration design are presented. Using this method, orbit elements of a ll the satellites in the formation can be solved directly, on condition that the reference orbit is a circular orbit or an elliptic orbit. At last, two typical examples of formation configuration design are given. Related Articles | Metrics

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Study on Performance Improvement of Systems Using CSVS Me thod Shan Jinjun Liu Dun Qi Naiming Zhao Baoshan (School of Astronautics, Harbin Institute of Technology,Harbin 150001) 2003, 23 (01):  .  Abstract ( 1881 )   Save A new method to improve the performance of flexible sy stems by combining CSVS method with feedback controller is proposed. Its application needs onl y frequencies and damping ratios of closed loop and flexible modes and can be used to eliminate arbit rary vibration modes simultaneously , which may include controller induced, flexible vibration and other kinds of vibration. The stronger robustness of CSVS method to uncerta inty in frequency makes it more practicable in engineering. For a kind of flexib le single link, various large and damping ratio angle slewing strategies are des igned by applying CSVS method to feedback control loop. Numerical simulation and hardware experiments validate the effectiveness of this method.includecontrollerinduced ,flexiblev Related Articles | Metrics

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Approach of the Synthetic Effectiveness Evaluation of Satellite Systems Based on Fuzzy Reasoning Feng Shuxing Xiao Yelun (Beijing University of Aeronautics and Astronautics, Beijing 100083) Chen Haoguang (Institute of Command and Technology of Equipments, Beijing 101416) 2003, 23 (01):  .  Abstract ( 1566 )   Save Evaluating the synthetic effectiveness of Satellite Systems(SS) is an important task in developing, using and optimizing SS In this paper, a criterion system o f effectiveness for SS is given by use of system theorems, and the evaluation mo del and method of combined qualitative analysis with quantitative count based on satisfying degree fuzzy reasoning is studied in order to get a reasonable quant itative results of all the criterions. Related Articles | Metrics

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Distributed Genetic Algorithm Used in Optimization of Regional Coverage Satellite Constellations Wang Rui * Ma Xingrui ** Li Ming * ( *Chinese Academy of Space Technology, Beijing 100086) ( ** China Aerospace Science and Technology Corporation, Beijing 10083 0) 2003, 23 (01):  .  Abstract ( 1688 )   Save Good results can be realised for optimization of regio na l coverage satellite constellations by using Genetic Algorithm(GA) The calculat ion time is so long with using GA that it is discommodious to optimize a big con stellation. The Distributed Calculating (DC) taking advantage of the free calcul ating source of computer network can be used to solve this problem. DC models as well as the procedure are given. The example shows that the distributed GA is e fficient. The DGA method can also be generalized to other fields. Related Articles | Metrics