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25 October 2003, Volume 23 Issue 05 Previous Issue    Next Issue

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An Analytical Method for Controlling Near Circular Orbits Yang Weilian (Chinese Academy of Space Technology, Beijing 100086) 2003, 23 (05):  .  Abstract ( 1676 )   Save Most of application satellites are running in near circular orbits, and many of them need to be controlled. In real application, it is unnecessary to use the exact dynamic equation for controlling, because a variety of errors exists. Instead, one can take circular orbit approximation, making it easy to handle then a very simple analytic solution can be derived. In order to prove the effectiveness of simplification all the errors ignored during the process of simplifying are estimated. Related Articles | Metrics

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Research on Electric Depun Column-Array Antenna on Satellites Ye Yunshang Zhang Zhengguang (Chinese Academy of Space Technology, Beijing 100086) 2003, 23 (05):  .  Abstract ( 1761 )   Save The electrical despun antenna of circular array of 32 elements around a cylindrical surface for a spin stabilized satellite on the synchronous orbit is suggested in this paper. Each element is formed by a column of four radiating elements in a linear array. By means of switch matrix and digital variable power dividers, five contiguous elements are excited simultaneously to form the beam of covering the globe, and then the scanning about the spin axis of the satellite through the circle is obtained. The angular reference is given by the pulses of the earth sensors that is utilized for synchronization at every satellite turn.Gain ripple less than 1dB and beam steps 1 6° in the course of 0°～360° scanning have been obtained. Related Articles | Metrics

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Statical, Kinematical and Dynamical Approaches for Treating the Relative Attitude Motion of Flight Vehicles Xiao Yelun Chen Wanchun (Beijing University of Aeronautics and Astronautics, Beijng 100083) 2003, 23 (05):  .  Abstract ( 1552 )   Save The problem of flight vehicle relative attitude motion treatment is studied in detail in this paper. Three methods are presented for getting relative attitude of flight vehicle, the first one is statical, the second one is kinematical and the last one is dynamical. A theorem called theorem of composition of angular acceleration is specially derived as basis for dynamic method of relative attitude . The results can be used in the analytical study and numerical simulation of flight vehicle relative attitude motion and also provide the basis for the problem of guidance and control of flight vehicle relative motion for the future. Related Articles | Metrics

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Integrated Optimization Design for Trajectory/System Parameter of Low Earth Orbit Launch Vehicle Luo Yazhong Tang Guojin Liang Yangang Zhou Lini (College of Aerospace and Material Engineering, National Univ. of Defense Technology, Changsha 410073) 2003, 23 (05):  .  Abstract ( 1957 )   Save The system parameter design combining with the trajectory optimization design can efficiently improve the whole design performance of launch vehicle during its preliminary design. Considering engineering requirement a set of mathematical models for trajectory and system parameter integrated optimization design are developed. The optimization methods for launch trajectory of low earth orbit are discussed, and the optimal control problems are converted into parameter optimization problems by multiple parameterized methods. An adaptive combinatorial optimization algorithm for solving this integrated optimization design problems is put forward. The results show that the total takeoff mass, which is a very important index in designing launchers, can be reduced by 3 5%. The optimization models and corresponding software presented in this paper has been successfully applied in the engineering design. Related Articles | Metrics

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Three-Parameter Positioning Method of Two Geostationary Satellites System With Accuracy Analysis Yuan Wei (National University of Defence Technology, Changsha 410073) Jin Xuejun (The 2nd Range of Navy, Dalian 116024) 2003, 23 (05):  .  Abstract ( 2115 )   Save In this paper, the positioning precision affected by geometic relationship of two geostationary satellites is investigated. Three parameters, intersection angle, pitching angle and visual angle are designed to describe the geometic relationship of observation intersection. Based on that, a corresponding error propagation algorithm is proposed which can adapt to the bad positioning and bad measurement geometic relationship. At last the results are demonstrated by the simulation. Related Articles | Metrics

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Research on the Airborne SAR Motion Information Sensor Sun Yongrong Liu Jianye (College of Automation Engineering of Nanjing University of Aeronautics & Astronautics, Nanjing 210016) Chen Wu (Hong Kong Polytechnic University, Kowloon Hong Kong) 2003, 23 (05):  .  Abstract ( 1816 )   Save This paper proposes an improved Motion Information Sensor (MIS) Based on GNSS/SINS for SAR motion compensation. The MIS can provide not only the long term information with absolute accuracy, but also the short term data with high relative accuracy during SAR imaging. System design, error models and navigation algorithms of the MIS are introduced in the paper. The experiment results show that the MIS can provide accurate navigation information (position, velocity and attitude ) to meet the requirements of SAR motion compensation. Especially , the MIS is suitable for the case: the accuracy of airplane master inertial navigation system is too low or not configured. Related Articles | Metrics

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Research of CCSDS Lossless Image Compression Applied to Constant-Bit-Rate Channel Jiang Hongxu Zhou Xiaokuan (Beijing University of Aeronautics and Astronautics, School of Space Technology, Beijing 100083) 2003, 23 (05):  .  Abstract ( 1617 )   Save In the paper an effective image data lossless compression method is presented, which is mainly used for remote sensing image data transmitted via constant bit rate channel. The algorithm is composed of three parts, decorrelation preprocessor, adaptive entropy coder and output memory controlling. Decorrelation preprocessor comes from the theory of analyzing feature of local texture, the entropy coder is borrowed from lossless data compression recommendation given by the Consultative Committee for System (CCSDS), and the memory controlling is decided by actual condition of input and output channel. These problems of transmission error propagation and controlling of compressed data output buffer are all resolved effectively in the scheme. Related Articles | Metrics

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The Application of Adaptive Model Following Control in Flight Simulation Servo System Ge Hongjuan Wang Daobo (The College of Automation, Nanjing University of Aeronautics and Astronautics, Nanjing 210016) 2003, 23 (05):  .  Abstract ( 2046 )   Save In this paper, the adaptive model tracking control (AMFC) is studied and used in the flight simulation servo system for the non linear characterstics of the system and for the specific demands of the dynamic performances. Based on the discussion of the reference model selection, and AMFC algorithm is derived and applied in a flight simulation servo system. Experiment results show that the dynamic performances of the system are improved and its frequency band is widen significantly by using the AMFC algorithm. Related Articles | Metrics

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Wavelet-Based Self-Adaptive Edge Detection for Noisy Aerial Image Zhong Ping Luo Jianshu (National University of Defense Technology, Changsha 410073) 2003, 23 (05):  .  Abstract ( 2165 )   Save An algorithm used to detect aerial image's edge contaminated by addictive white noise is discussed. Using statistical characteristic of contaminated aerial image's wavelet coefficients and multi resolution decomposition of wavelet transform, shrinkage factors are constructed and used for treating the edge or noise separately. Furthermore, by evaluating three parameters of wavelet coefficients' probability model using maximum likelihood method, self adaptively of the algorithm is achieved. The result of the detecting edge of contaminated aerial image by this method is satisfactory . Related Articles | Metrics

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Simulation and Research on the Satellite Autonomous Celestial Navigation Based on the Perturbative Orbit Zhang Yu Fang Jiancheng (Beijing University of Aeronautice and Astronautics, Beijing 100083) 2003, 23 (05):  .  Abstract ( 1760 )   Save This paper studies the method of the autonomous satellite celestial navigation by sensing Stellar Horizon of Atmospheric Refraction In order to establish the exact motion model, the 2nd zonal harmonic of the nonspherical earth gravity is introduced to the system equation The measurement equation with the refraction height as the observation is established based on the spherically-layered atmosphere with the exponential density The computer simulation is processed after establishing the Extended Kalman Filter equation The detailed error analysis of the simulation result is presented The result illustrates that the higher precision can be obtained using satellite autonomous celestial navigation by sensing stellar horizon of atmospheric refraction based on the perturbative orbit Related Articles | Metrics

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A Fusion Algorithm to Estimate the Rates of an Object Using Tracking and Telemetered Data Zhu Zhuanmin Yang Yikang Huang Yongxuan (Xi′an Jiaotong University, Xi′an 710049) Li Jisheng (Xi′an Satellite Control Center, Xi′an 710043) 2003, 23 (05):  .  Abstract ( 1733 )   Save This paper built transformation relationship between the launch system and inertial frame. The method for computing the gravitation acceleration based the telemetered data is discussed . Then proposed a fusion algorithm to estimate the rates of a object using tracking and telemetered data. The simulation demonstrates that the accuracy can be improved greatly by using telemetered data to estimate the rates and it will offer a methodical foundation to overcome related problems in data processing. Related Articles | Metrics

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The Direct Shooting Method Solving Finite-Thrust Trajectory Optimization Wang Hua Tang Guojin Lei Yongjun (College of Aerospace and Material Engineering, National University of Defense Technology, Changsha 410073) 2003, 23 (05):  .  Abstract ( 2488 )   Save The direct shooting method solving finite thrust trajectory optimization is studied. The basic method of converting optimal trajectory problems into parameter optimization problems using direct shooting method is introduced, and the transformation method of state and control equality (or inequality) constraints are proposed. The error during transformation process due to interpolation and numerical integration is analyzed particularly. At last, an optimal rendezvous is used to demonstrate the effect of different node numbers and integration steps to final result. Related Articles | Metrics