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25 February 2005, Volume 25 Issue 01 Previous Issue    Next Issue

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Fast Maneuver Control of Flexible Satellite System Zhang Honghua Li Kang Zhao Yu (Beijing Institute of Control Engineering, Beijing 100080) 2005, 25 (01):  .  Abstract ( 1758 )   Save Fast maneuver of flexible satellite system often requires large attitude changing with reduction of vibration. In this paper, pulse sequence control methodology is presented based on unconstrained mode equations to suppress residual vibration; besides, pulse sequence programming is proposed to minimize maneuvering time. The methods can meet the requirements of the fast maneuver and without residual vibration after maneuvering. Moreover, it is very suitable to satellite systems equipped with on off jets and reaction wheels. Finally, numeric simulation is explored to verify the validity of pulse sequence control. Related Articles | Metrics

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Video Coding Using 3D SPECK Chen Yuyun Luo Jianshu (National University of Defence Technology, Changsha 410073) 2005, 25 (01):  .  Abstract ( 1742 )   Save In this paper, a new embedded 3D wavelet video coding method with 3D SPECK is considered. The method is based on real 3D wavelet packet transform, and implements a three dimensional extension of SPECK in still image coding by defining a new block structure. The method does not involve motion estimation, and has lower computational complexity and coding latency , and can make full embedded video streams. Experimental results show that the method is able to compress video rapidly and effectively, and is a video coding method with great potentials. Related Articles | Metrics

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Arcjet Plume Plasma Measurements Using Electrostatic Probe Zhao Wenhua Shi Yong Shen Yan (Tsinghua University, Beijing 100084) 2005, 25 (01):  .  Abstract ( 1527 )   Save Arcjet attracts more and more researchers today, because its specific impulse is higher than the thrusters with chemical propellants. A electrostatic probe diagnostics system used in vacuum environment, for the measurement of the electronic temperature of the Arcjet plume plasma is established. The electronic temperature of the Arcjet plume, with argon as the propellant , is measured by this system, and the axial and radial distribution electronic temperature of plume is obtained. The result shows that the electronic temperature is much higher than the heavy particle temperature in the axis of the Arcjet plume. Related Articles | Metrics

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Design Methods for the Closing and Fly-around of Space Rendezvous Zhu Renzhang Tang Yi (Beijing University of Aeronautics and Astronautics, Beijing 100083) 2005, 25 (01):  .  Abstract ( 1799 )   Save Design methods for the closing and fly around are investigated in this paper. The universal forms are derived, by which the chaser can transfer from a holding point to another one in V bar within any duration of flight. The different methods of transfer from V bar to R bar or H bar are designed, and their characters are compared according to the transfer duration and velocity increment. Related Articles | Metrics

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Two Design Schemes of Temperature Control for Motion Simulator in Space Environmental Simulator Yang Chunxin Han Haiying Zhang Lina (Beijing University of Aeronautics and Astronautics, Beijing 100083) Li Gao (Beijing Institute of Spacecraft Environment Engineering , Beijing 100029) 2005, 25 (01):  .  Abstract ( 1915 )   Save The heat exchange method for cooling motion simulator based on initial ventilating cooling method is presented in this paper. The flow field and temperature field in two different motion simulators are simulated using CFD method. Furthermore, for the validation of heat exchange cooling method, the theoretical design of heat exchange cooling method is effective and can improve the gas flow and heat transfer of motion simulator. Related Articles | Metrics

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Research of Remote Image Lossly Compression in Control Zeng Yong (China Center for Resources Satellite Data and Applications, Beijing 100830) Yan Ronghua (National Geomatics Center of China, Beijing 100044) 2005, 25 (01):  .  Abstract ( 1940 )   Save In the domain of surveying and mapping , users present rigorous requirements for the image quality. But there are noises in the image data, so lossy compression is feasible. In this paper, a method of remote image lossy compression in control is presented. First, the feasibility of remote image lossy compression is analysed. Then the method of two layer and two dimension wavelet transform to decompose original image is adopted, and 7 high frequency quantizers according to remote image's feature is created. At last, the relation between the compresion ratio and peak peak SNR at the different high frequency quantizers is stakied. Related Articles | Metrics

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The Fractal Feature of Space Object RCS Huang Xiaohong Qiu Zhaokun Chen Zengping (National University of Defense Technology, Changsha 410073) Zhang Zhenzhong (The Chinese People's Liberation Army, Kuerle 841001) 2005, 25 (01):  .  Abstract ( 1767 )   Save RCS of space object is nonstationary time series, it is difficult to do feature extracting using common time series analysis methods. Fractal Brown Motion model is used in this paper for feature extracting. The results using real data show that fractal cimension of RCS is a useful feature for space object target recognition. Related Articles | Metrics

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The Method of Mission Planning of the Ground Station of Satellite Based on Dynamic Programming Liu Yang Chen Yingwu Tan Yuejin (National University of Defence Technology, Changsha 410073) 2005, 25 (01):  .  Abstract ( 1693 )   Save The mission planning of satellite and its applications system is a main content of spaceresource management. This paper gives the model of mission planning of ground station with single antenna, considering the time windows constraints, mission privilege and setup time of antenna with the maximum uses of the resources. And then, it gives a dynamic programming method to solve the model. At last an example is given to validate the model and solution. Related Articles | Metrics

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Numerical Investigation on Evaporator for CPL Qian Jiyu Li Qiang Xuan Yimin (Nanjing University of Science & Technology, Nanjing 210094) 2005, 25 (01):  .  Abstract ( 1654 )   Save A two dimensional numerical model is developed to simulate the dynamic and thermal behavior and to estimate the performance of the evaporator of a CPL. The vaporization problem of the working fluid is handled with using enthalpy equation, which avoids using time consuming selfadaption mesh techmique but is easy to track and maintain the liquid vapor interface, so it is convenient to handle with the capillary force in porous medium. The introducing source term in the momentum equations, which acts different capillary force is calculated at different liquid vapor fronts. Numerical results under different working conditions are presented. Related Articles | Metrics

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Analysis for Vibration of Side Viewing Mirror in Satellite Camera and Its Effect in Microgravity Lin DeLuo (Beijing Institute of Space Machine & Electricity, Beijing 100076) 2005, 25 (01):  .  Abstract ( 1628 )   Save This paper presents the image oscillation of CBERS 02 CCD camera in ground test and its effect on image quality, and the reason oscillation is due to the vibration of the side viewing mirror. The vibration mechanism is discussed as follow: the spring of the worm wheel elasticity and the worn spring forms a integrate spring and becomes a resonant system. In resonant condition, the outside disturb will be magnified. Thus the method for decreasing or overcoming vibration of the mirror is got. Besides, in orbital condition the camera image quality are fine. It shows that the vibration of the mirror has been overcomed, which explains that the vibration of the mirror does not increase in microgravity. Related Articles | Metrics

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The Study on Multi-Stage Fault Detection and Isolation in Integrated Navigation System Liu Zongyu Chen Ming Wang Wei (Automation School of Northwestern Polytechnical University, Xi'an 710072) 2005, 25 (01):  .  Abstract ( 1512 )   Save In this paper, fault detection and isolation in the integarted navigation system are discussed. And the 5 stage fault detection algorithm, in cluding built in test (BIT), rationality test for outputs of sub systems, correlation test among outputs of sub systems, test for residuals in Kalman filter and rationality test for estimation of error obtained by Kalman filter, is proposed. This algorithm is effective and can be easily implemented with low computation cost. It has been applied to integrated navigation system and increases its reliability remarkably. Related Articles | Metrics

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An Assessment of Image Quality Based on Modern Communication Theory Shi Hongwei Chen Shiping (Chinese Academy of Space Technology, Beijing 100081) 2005, 25 (01):  .  Abstract ( 1670 )   Save The modern communication theory is used in the analysis of imaging systems. The object information density model is built for analogue and digital image respectively. The utility of sub pixel technology is evaluated with the increment of object information density. This model is applied in the design of linear array CCD camera, the effect of the system's modulation transfer function (MTF) and signal to noise ration (SNR) on the quality of images is studied. It is found that the image's object information density would improve with the lift of SNR, and the effect of MTF is related with object's characteristics. Related Articles | Metrics