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25 April 2006, Volume 26 Issue 02 Previous Issue    Next Issue

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Method of Selecting Ranging-Codes for Navigation Satellites Shuai PingQu Guangji Chen Zhonggui(China Academy of Space Technology,Beijing 100094) 2006, 26 (02):  1-9.  Abstract ( 1746 )   Save The classical method of selecting ranging-codes is based on the finite field theory so that the range of selecting combination codes is much small,and it is also very difficult to obtain the enough code number and better cross-correlation performance.Therefore,an!algorithm of searching the m sequences and their preferred pairs in the global field is presented in this paper.Meanwhile,three schemes to generate the ranging codes of navigation satellites are also discussed in detail.All ranging-code sequence combinations can be gotten by using the algorithm.And then the ranging-code sequences with enough number and better cross-correlation performance can be generated from the selected Gold code family.Finally,by comparing the selected ranging-codes with GPS C/A codes on the assignable code number and auto-and cross-correlation features,the advantage of the selected ranging-codes and the feasibility of the algorithm can be illustrated preliminarily. Related Articles | Metrics

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Optimal Design and Analysis of Concomitant Satellite Formation for Spaceborne InSAR Meng Yunhe~1 Chen Rongjuan~2 Dai Jinhai~1(1 College of Aerospace and Material Engineering,National University of Defence Technology,Changsha 410073)(2 Dalian Naval Academy,Dalian 116018) 2006, 26 (02):  10-16.  Abstract ( 1899 )   Save Height measuring by master satellite and concomitant satellite formation InSAR system being the background,the problem of the concomitant satellite formation configuration optimal design is studied.Firstly,the criterionof optimization is defined as maximumtime ratio of effectual observationwhich describes the measurement performance in a whole orbit period. Correspondingly the CartWheel-like satellite formations are focused on,in which satellites are in the same concomitant orbit around the virtualcenter with symmetrical distribution.The ratioof two amplitudes and the difference of two phases in relativemotion are served as variables of optimization.By a numerical simulation a figure is found out,which shows the relation between the criterion of optimization and the variables of optimization.The orbit elements of the satellites in the best configuration are provided. Then the method estimating fuel consumption for formation keeping and orbit maintaining is given and the necessaryfuel mass of the best configuration for a period one year is calculated.Last a beneficialconclusion is drawn,which will be of some help to the optimizationof whole InSAR system. Related Articles | Metrics

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Algorithms of Collision Probability between Spacecraft and Short-Term Debris Clouds Wang Ting Dong Yunfeng(Beijing University of Aeronautics and Astronautics,Beijing 100083) 2006, 26 (02):  17-23.  Abstract ( 1932 )   Save The collision probability between spacecraft and debris clouds are studied.Different kinds of collision probabilities are mentioned,and methods to convert these probabilities are described. General methods for calculating impact probability are introduced in the case that orbit errors are not considered.Simplified algorithms are described based on C-W equation,which are valid in short time.These simplified algorithms are verified by Monte Carlo method. Related Articles | Metrics

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Robustness Assessing of Unpowered Autolanding Trajectory Sun Chunzhen Huang Yimin Guo Suofeng College of Automation Engineering,Nanjing University of Aeronautics and Astronautic,Nanjing 210016 2006, 26 (02):  24-29+51.  Abstract ( 1850 )   Save The uncertainties in aerodynamics and initial conditions are considered for assessing the robustness of the trajectory.The approach of assessing the robustness is the same algorithms used in designing the original auto landing trajectory,i.e.the method based on the 3 degrees-of-freedom nonlinear equations of motion which governing dynamic pressure.The energy potentialis defined as the measure of the ability to increase and decrease energy to remove energy dispersions.The touchdown characters,the allowable uncertainties in aerodynamics and dynamic pressure disturbance rejection are assessed when in the presence of uncertainties in aerodynamics.The result showsthat the trajectory is robust. Related Articles | Metrics

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Orbit Dynamics Analysis of Solar Spacecraft Wang Songxia Xu Shijie Chen Tong School of Astronautics,Beijing University of Aeronautics and Astronautics,Beijing 100083 2006, 26 (02):  30-37+43.  Abstract ( 1894 )   Save A sail force control algorithm is proposed,first analyzing the acceleration components to determine which one affects the orbit elements most and then continuously orienting the sail to maximize the solar radiation pressure SRP force along the direction of this component.Then through the analysis of the interactional relations of the orbit elements when they are modified,a control strategy is proposed to correct several orbit deviations at the same time.The oblateness perturbation of the Earth J_2 term only,as well as the gravitational perturbation of the sun and the moon is considered in the numerical simulation,while atmospheric drag and shadowing effects of the Earth are neglected.Numerical results indicate that using a solar sail to fulfill the task of orbit corrections is feasible.Furthermore,an appropriate orientation of the sun is a necessary condition of quick and efficient orbit modification. Related Articles | Metrics

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An Accurate and Steady Alternating Current Servo System of Satellite Antenna Qi Rong Zhou Suying Lin hui Chen Ming Northwestern Polytechnical University,Xi'an 710072 2006, 26 (02):  38-43.  Abstract ( 1692 )   Save The driver is the core part of the satellite antenna.An Alternating Current servo system for making rotary antenna at an accurately constant speed.Based on the design ideas of the polygon flux linkage locus,construct is used to get the switch table of three-phase inverter.The hardware and software of the system have been designed and debugged on the CPU of special motor controller-TMS320F240.Simulation result shows that the error of angle measure is within ±0.07° and precision of scan cycle can be within ±0.34ms in this system. Related Articles | Metrics

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Design on Constant Volume and Conductance Method Calibration System for Throughput Zhang Dixin Guo Meiru Zhao Lan Zhao Dingzhong Lanzhou Institute of Physics,Lanzhou 730000 2006, 26 (02):  44-51.  Abstract ( 2016 )   Save The constant volume and conductance method calibration system is a metrology standard for low range throughput.The calibration system is composed the constant volume flowmeter and the conductance method.The constant volume flowmeter can measure more gas flow and the conductance method can measure small gas flow.The constant volume flowmeter has two work modes.It can measured inflow or outflow gas flow from the constant volume.The vacuum leaker can be calibrated with the constant volume and conductance method.The calibration range is 5×10~ -2~5×10~ -11Pa·m~3/s,the combined standard uncertainty is 0.56%~1.70%. Related Articles | Metrics

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The Design and Analyses of Close Cable Loop of Solar Array Li Weituo College of Aerospace and Material Engineering,National University of Defense Technology,Changsha 410073 2006, 26 (02):  52-57.  Abstract ( 1810 )   Save The close cable loop CCL is commonly used as a synchronous deploying control mechanism of solar array.The preload tension of CCL cable affects the synchronization of deployment directly.By simulation of deploying dynamics,the preload tension of CCL cable of solar array is designed.In addition,the deployment process of solar array is analyzed by simulation,shown that the result of preload design in CCL is rationality. Related Articles | Metrics

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An Integrated Model for Dynamic Behavior of CPL Qian Jiyu Li Qiang Xuan Yimin Nanjing University of Science & Technology,Nanjing 210094 2006, 26 (02):  58-64.  Abstract ( 1577 )   Save A transient model of a CPL has been developed to predict the thermal and dynamic behavior.This model comprises two coupled modules: the thermal module and the hydrodynamic module.The objective of this numerical model is to study the mechanisms of the unstable behavior during the cyclical functioning of the CPL.The simulative processes include the start-up,the temperature oscillations in the reservoir and the heat load change in the evaporator.The numerical results agree with the experimental data.Moreover,this model is used to explain the reason that the start-up becomes a failure easily,the abrupt change of the heat load can lead to the evaporator deprime.It also can reveal that the temperature oscillations in the reservoir are disadvantageous to the operation of CPL. Related Articles | Metrics

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Application of Hardware/Software Co-Design in Remote Terminal System Design Lu Feng An Kai Sui Zhiguang Shandong Aerospace Electro-technology Institute,Yantai 264000 2006, 26 (02):  65-70.  Abstract ( 1786 )   Save Firstly,system′s hardware and software are model unified.Then an estimated time performance method based on dynamic programming,and a linear-weight sum method to construct the fitness function′ way are presented,and combining them with genetic algorithm to solve hardware/software partitioning problem.Finally,simulates the illustration,and the result shows that the method can solve multi-object optimization design effectively. Related Articles | Metrics