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25 February 2004, Volume 24 Issue 01 Previous Issue    Next Issue

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Dynamic Modeling and Analysis of Deployable Truss System Miao Bingqi * Qu Guangji ** Yang Lei ** Liu Yinhu * (*College of Mechanical and Electrical Engineering, Zhejiang University of Technology, Hangzhou 310014) (**Chinese Academy of Space Technology, Beijing 100086) 2004, 24 (01):  .  Abstract ( 2326 )   Save A dynamic model for a kind of deployable truss systems is derived. The method for solving the derived nonlinear differential-algebraic equation system is provided. An example is given to simulate the deployment of a typical truss system. It is shown that the derived model and the provided method for solving the dynamic equations are efficient for the truss system deployment simulation. The difficulty encountered in applying the commercial dynamic software can be avoided. Related Articles | Metrics

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Discussion of Data Security About Space-Earth All-in-One Networking and Analysis of CCSDS SCPS Liu Yong Dong Yong (Shandong Institute of Aerospace Electronic Technology, Yantai 264000) Li Zehui (Naval Engineering College Aeronoutics, Yantai 264001) 2004, 24 (01):  .  Abstract ( 1683 )   Save The hugely successful architecture and protocols of internet operate poorly when faced with operating environments such as long delays, excessive loss, network partitioning, or short node lifetime. Such problems are typically found in extreme space environments which lack infrastructure or under severe constraints such as limited power. This paper primarily addresses characteristics of space communication network on the base of quantitative analysis, brief synthesis is performed for Consultative Committee for Space Data System(CCSDS) Space Communications Protocol Specification(SCPS), and a model accounting for data security problem of space-earth all-in-one networking is provided. Related Articles | Metrics

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Application of Programmable System-on-A-Chip for Small Satellite Computers Zheng Daixun Tanya Vladimirova (England Surrey Space Centre) 2004, 24 (01):  .  Abstract ( 1917 )   Save Small Satellites aim to achieve low-cost, lightweight and fast access to space and this is normally supported by the use of commercial-off-the-shelf components and development tools. System-on-a-programmable-chip is a major enabling technology. Such a single-chip solution to the core data handling, communications and control systems will dramatically reduce size, complexity and cost of small satellites electronics. This paper is concerned with the implementation of a small satellite on-board computer (OBC) on a single programmable logic chip. Integration of soft intellectual property cores forming a main subsystem of the system-on-a-chip OBC (SoC-OBC) is detailed. A XILINX Virtex Field Programmable Gate Array (FPGA) is used for prototyping of the SoC. This single-chip OBC is composed of Microprocessor IP Core and other soft peripheral IP core. Implementation methods and results would be described and demonstrated in this paper. Related Articles | Metrics

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The Effect Analysis of Yaw Steering′s Compensation for Doppler Shift of SAR Satellite Meng Yunhe Yin Qiuyan Dai Jinhai (College of Aeronautical and Material Engineering, National Univ. of Defense Technology, Changsha 410073) 2004, 24 (01):  .  Abstract ( 2221 )   Save The Doppler shift of SAR satellite is related to the relative motion between the satellite and the target. Based on the orbit mechanics theory the Doppler shift is splited into two parts: one has relation to the yaw angle that the be compensated and the other has nothing to do with it that can only be viewed as noise. First analytical solution for yaw steering is deduced and simplified to fit for real time computing. Then the concept of compensation effect is defined and the yaw steering's compensation effect is estimated by analysing the two parts, at the same time the results of simulation indicate that the method of theoretical estimation is conditionally effective. The relation between compensation effect and the orbit eccentricity or the elevation angle is also discussed. Last a conclusion about the effect of orbit elements and radar parameters on compensation is drawn to support the primary design of SAR satellite. Related Articles | Metrics

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Study on the Doppler/SINS Integrated Navigation System Based on the Assistance of RDSS Lin Xueyuan * Zhang Limin * Liu Jianye ** Li Yuguang * (* Navigation research center, Nanjing University of Aeronautics and Astronautics, Nanjing 210016) (** Naval Aeronautics Engineering Academy, Yantai 264001) 2004, 24 (01):  .  Abstract ( 1871 )   Save The advantages of the integrated navigation system of Doppler/SINS are less output level velocity errors and less errors of level angles, but the bigger shortcoming is longitude and latitude errors. So it can not be used as the unique navigation positioning system. The Double-Star positioning system (RDSS) can output the longitude and latitude information with hiqher precision, but with the shortcoming of position lag. lf the output level velocities of the Doppler/SINS integrated navigation system are used to compensate for the position lag of RDSS then RDSS after compensated can correct the Doppler/SINS system in real time. The simulation results show that the Doppler/SINS system based on the assistance of RDSS can effectively overcome the shortcoming of the Doppler/SINS system, and is a new integrated navigation system which can be used in the case that needs the high precision of navigation position. Related Articles | Metrics

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Geometric Characters of Inter Satellite Links Between MEO Layer and LEO Layer in MEO/LEO Networks Wang Liang Zhang Naitong Wang Yang Chu Haibin Li Hui (Harbin Institute Technology Communication Research Center,Harbin 150001) 2004, 24 (01):  .  Abstract ( 1687 )   Save The MEO/LEO satellite network is the important part of future mobile satellite communication system. The inter-layer ISL of MEO/LEO satellite network is an essential factor which effects the performance of the satellite network system. This paper describes geometric characters (including range, elevation angle and azimuth angle) of inter-ISL in MEO/LEO satellite network in order to design efficient tracking system of satellite's antenna and the dynamic routing strategy in MEO/LEO satellite network. Related Articles | Metrics

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The Application of Fuzzy Inference Based on Component in the Satellite Fault Diagnosis Chen Hongbo Song Zhengji Jiang Xingwei (Harbin Institute of Technology, Harbin 150001) 2004, 24 (01):  .  Abstract ( 1530 )   Save In this paper using COM technique to realize components of fault diagnosis and integrating fuzzy inference technique with fault diagnosis technique, the component platform of satellite fault diagnosis is introduced and exploited fuzzy inference component is developed. Fuzzy inference component is applied to fault diagnosis expert system of power wastage in power system of a satellite. Related Articles | Metrics

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Strict and Speedy Transformation From Geocentric Coordinates to Geodetic Coordinates for the Spacecraft Li Zhi * Zhang Yasheng ** Li Yanxing * Zhang Jinghua * Zhang Zhongfu * ( *First Monitoring Center, China Seismological Bureau, Tianjin 300180) ( **College of Equipments and Commands, Beijing 101416) 2004, 24 (01):  .  Abstract ( 1569 )   Save Within the meridian plane at any point in the space, the normal equation from the point to the Earth's meridian ellipsoid is established. With the geocentric coordinate at the intersection point of the normal and the meridian ellipsoid as the parameters for calculation, the approximate algorithm and strict algorithm for the geodetic height and geodetic latitude are derived. The approximate algorithm is very simple, which can be accomplished by a hand calculator with the trigonometric function. For any point with the height lower than 36000km, the accuracy of h and B can be better than 31m and 0 17° respectively. Taking the intermediate result by the approximate algorithm as the initial value, the calculation of geodetic coordinates can be transformed into a binary first-order equation that can be solved simply. If PC is used, the calculation of a number of spatial points can be accomplished in a moment and the geodetic coordinates that are the same as the true values can be obtained, which provided a support of new technology for the real-time speedy coordinate calculation for the spacecraft. Related Articles | Metrics

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Realization and Research of Low Order Kalman Filter for the Low-Cost SIAHRS Lai Jizhou Liu Jianye Lin Xueyuan Xiong Zhi Zeng Qinghua (Navigation Research Center, Nanjing University of Aeronautics and Astronautics, Nanjing 210016) 2004, 24 (01):  .  Abstract ( 1633 )   Save In the engineering application of navigation system, high order filter can bring a heavy burden to navigation computer, and also bring serious mode error, which will influence the filter's accuracy and performance. This paper mainly introduces the design and realization of reduced order kalman filter for the low-cost Strapdown Inertial Attitude and Heading Reference System (SIAHRS). The structure of the low order filter is presented, which mainly aim at the SIAHRS, and its yaw can be modified through magnetic sensor. This paper discusses SIAHRS's composition in which the reduce order filter is actually used.The result indicates that the presented reduce order filter can ensure accuracy of SIAHRS, and has great value of application with widely prospects. Related Articles | Metrics

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Shaped-Beam Reflector Design for Data Transmission of Earth Resource Satellite Zhang Zhengguang Ye Yunshang (Chinese Academy of Space Technology, Beijing 100086) 2004, 24 (01):  .  Abstract ( 2056 )   Save The shaped reflector for a low-orbital earth resource satellite is synthesized using geometrical optics in this paper. The secondary radiation patterns of the reflector are calculated based on physical optics technique, and the reflectors is optimized for obtaining the earth-matched beam. Two different boundary conditions are offered in synthesis of the reflector, and the corresponding calculated results are given and compared with each other. The effect of the blockage of feed on the secondary radiation pattern is studied. The calculated results agree well with the tested results. Related Articles | Metrics

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A Method of the Observable Degree Analysis of Integrated GPS/SINS Navigation System Shuai Ping (Chinese Academy of Space Technology, Beijing 100086) Chen Dingchang Jiang Yong (China Aerospace Science & Industry Corporation, Beijing 100854) 2004, 24 (01):  .  Abstract ( 2026 )   Save The observable degrees of the system states are the key indexes to check the convergence accuracy and velocity of designed Kalman filter. First, the observability analysis method of piece-wise constant system(PWCS)and the observable degree analysis method of the system states based on the singular value decomposition are described respectively in this paper. And then the integrated GPS/SINS navigation system can be demonstrated to meet the law of PWCS analysis method. In order to analyze the observable degrees of linear varying-time system states along a whole trajectory, the modified analysis method will be presented further. Finally, its rationality and feasibility can be shown by a simulating example. Related Articles | Metrics

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A New Method of Autonomous Navigation for Deep Space Explorer Based on Information Fusion Ning Xiaolin Fang Jiancheng (School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 10083) 2004, 24 (01):  .  Abstract ( 1665 )   Save Celestial navigation is one of the important methods of the deep space probe to realize autonomous navigation. Based on the orbit kinetic equation and the observation information to the orb, at the same time using the Kalman filter to accurately estimate the position and velocity of the spacecraft. But these angle measurements can't provide enough information to estimate the position of explorer with a high precision. This paper presents a new method of autonomous navigation which using both the celestial method and one-way Doppler measurement from ground stations based on information fusion. The simulation results show that the high precision of position determination can be obtained. Related Articles | Metrics