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    25 December 2008, Volume 28 Issue 06 Previous Issue    Next Issue
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    State Least-square Estimation of Relative Orbit Modification Point for Following Spacecraft
    Guo Bibo1,2 Liang Bin1 Qiu Yue1 Qiang Wenyi2(1 Institute of Space Intelligent System,Harbin Institute of Technology,Harbin 150001)(2 Astronautics School,Harbin Institute of Technology,Harbin 150001)
    2008, 28 (06):  1-7. 
    Abstract ( 1541 )   Save
    The relative navigation of long-term following spacecraft in near-circular orbit was researched.For relative orbit modification at fixed time,the least-square estimation was used to derive the relative position and velocity of the fixed time.Based on the feature of model error,the algorithm was improved by weighted least-square.The new algorithm was simply and flexible.Numerical simulation result shows that the performance of the weighted least-square estimation is comparative with that of the Kalman filter,and the precision of the relative state estimation satisfies orbit modification for long-term following spacecraft.
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    Control Strategy Using Atmospheric Drag for Along-track Formation Maintenance
    Chen Tong1 Xu Shijie1 Li Kehang2(1 Beijing University of Aeronautics and Astronautics,Beijing 100083)(2 Beijing Institute of Control Engineering,Beijing 100080)
    2008, 28 (06):  8-13. 
    Abstract ( 1899 )   Save
    A maintenance control strategy for formation spacecraft flying in a near-circular orbit with fixed along-track distance tolerance was presented.By using the classical orbit element differences method,the periodic characteristics of relative motion and the influence of atmospheric drag on relative motion were analyzed.Using the relative drifts of along-track motion caused by atmosphere drag,the initial semi-major axis difference and the expected semi-major axis differences at the bounds of along-track tolerance box for the long time formation maintenance were designed.Afterwards,the along-track maintenance impulsive delta-velocities implemented at the bounds were given.Numerical simulation results indicate that the formation maintenance control strategy is feasible and requires fewer times of impulse and less velocity increment.Furthermore,the control algorithm is simple to be implemented autonomously by spacecraft.
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    Research on the Perturbed Three-body Problem
    Li Mingtao Zheng Jianhua Yu Xizheng Gao Dong(Center for Space Science and Applied Research,Chinese Academy of Sciences,Beijing 100080)
    2008, 28 (06):  14-20. 
    Abstract ( 2138 )   Save
    Since the circular restricted three-body problem model ignores the effect of perturbations,it can not accurately describe the dynamic characters of the three-body system.The dynamic characters and orbit design strategy of the perturbed three-body problem model was studied.Firstly,main perturbations of libration point missions were analyzed,and then the general dynamic equation of the perturbed three-body problem in the synodic frame was concluded from the dynamic equations in the inertial frame considering the effects of the eccentricity,the gravity of the fourth body and the solar radiation pressure.Finally,the two level differential corrections method was proposed to transform the orbit designed under the circular restricted three-body problem model into the perturbed three-body problem model.
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    Modeling and Analysis of Spatial States and Inter-Satellite Baseline in Formation Flying Missions
    Yao Jing1 Gu Defeng2 Yi Dongyun2 Zhu Jubo2(1 College of Computer,National University of Defense Technology,Changsha 410073)(2 College of Science,National University of Defense Technology,Changsha 410073)
    2008, 28 (06):  21-28. 
    Abstract ( 1844 )   Save
    The inter-satellite baseline plays a vital role in the formation flight satellites missions.The appropriate spatial states were chosen to determine the inter-satellite baseline based on the precision requirements.A mathematical model was established to associate the spatial states and the inter-satellite baseline.An error analysis method was also presented.Simulations in certain scenarios were carried out.The index such as the precision influence factor was calculated to depict the propagation relations between the two kinds of parameters.The baseline length was only correlated with the relative spatial states of the formation flight satellites,while the baseline angles were also correlated with the absolute attitude of the master satellite.The errors were amplified during the propagation from the satellite spatial states to the inter-satellite baseline.
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    Real-time Optimization Algorithm for LEO Satellite Network Service Area Allocation
    Han Zhendong Wang Yue Ma Zhengxin Shan Xiuming(Tsinghua University,Beijing 100084)
    2008, 28 (06):  29-34. 
    Abstract ( 1706 )   Save
    Due to its global coverage,LEO(Low-Earth-Orbit) satellite network is becoming more and more important for providing Internet and other services.However,a main technical challenge about LEO satellite is how to design a reasonable and efficient mechanism to optimize its Service Area Allocation.The difference between Footprint and Service Area were analyzed.It pointed out that the traditional allocation mechanism would lead to the mismatch between service requirements and LEO satellite network capacity.To improve the situation,an on-board real-time Service Area Optimization Algorithm(SAOA) was proposed and the simulation results prove that,SAOA can alleviate the mismatch between service requirements and network capacity,reduce the blocking probability and improve the network performance significantly.
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    Spacial Gyroscope Calibration Algorithm Based on Obserbability Analysis and Model Predicition
    Xu Fan Fang Jiancheng Guo Lei(School of Instrument and Optoelectric Engineering,Beijing University of Aeronautics and Astronautics,Beijing 100191)
    2008, 28 (06):  35-40. 
    Abstract ( 1694 )   Save
    When mobile special maneuver platform working on the long-term tracking,fiber-optic gyroscope can meet the demand in the space due to its advantages.Fiber-optic gyroscope self calibration should be done in the space.High fidelity gyro models cost more computation time and usually reduced module filter lost navigation precision.Aimed at the problem,using sensor observation to analyze the high-dimension gyroscope module and taking the states with low observability as model errors,a reduced-dimension module based on module prediction was proposed.The proposed module could guarantee the precision,decrease the computation and improve the algorithm speed.The hardware-in-the-loop simulation results show that the algorithm has higher precision than that of the high-dimension self calibration algorithm,and its computational cost is only 1/10 of the full-dimension model.The algorithm also improves the real-time performance.
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    Frequency Domain Detection Method for Galileo Search and Rescue Beacon Signal
    Zeng Hui Li Jilin(Satellite Application System Department ofChina Academy of Space Technology,Beijing 100086)
    2008, 28 (06):  41-44+51. 
    Abstract ( 1634 )   Save
    The Galileo Search and Rescue system is a part of the Global Satellite Search and Rescue System(COSPAS-SARSAT),which is carried on the Galileo navigation constellation.Using the Galileo Search and Rescue system,the distress signal can be localized and then rescue activity can be executed.The signal to noise ratio of satellite transmitted signal by is very low,so it is extremely important for the operation of search and rescue system that whether it is able to detect signal under the condition of low signal to noise ratio.In order to solve this problem,a frequency domain detection method based on FFT operation was presented.The theoretical analysis and simulation verification show that the satellite signal can be effectively detected under low signal to noise ratio using this method.
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    Influence of Inflation Conditions Parachute Inflation
    Guo Shuwei Dong Yangbiao Wang Haitao Qin Zizeng(College of Aerospace and Material,National University of Defense Technology,Changsha 410073)
    2008, 28 (06):  45-51. 
    Abstract ( 1947 )   Save
    The parachute axis of symmetry equation and radial equation were rationally simplified.Integrated with other experienced formulas,the movement process of parachute inflation was described.The influence of atmosphere density and initial velocity on the parachute inflation times,inflation distance and max strain of suspension-line were analyzed by the simplified model.The result is importance to design of Mar parachute and simulate conditions of varied type parachute inflation experimentation.
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    Design and Implementation of Ground Test System for Astronaut Extravehicular Activities
    Cui Junfeng Yang Gaofeng Gong Jie Shao Rongping Yu Qianxu He Honghui Yin Dayong(Environment Engineering Department,China Academy of Space Technology,Beijing 100094)
    2008, 28 (06):  52-55+63. 
    Abstract ( 1835 )   Save
    Ground test facilities to validate astronauts′ suit must be built in order to achieve the Extravehicular activity.The article describes the system design and its capability index,also presents the practical process curve of astronauts Extravehicular activity.It is indicated by the result that the ground test facilities can suffice the request of Ex-vehicle activity test.The space environment capacity has been stepped up by the conclusion,and the ability of sequential manned space environment in ground has also been guaranteed.
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    Effects of User Altitude on the Performance of DRS Inter-orbit Communications Link
    Hu Dan Yan Zhongwen(China Academy of Space Technology,Beijing 100094)
    2008, 28 (06):  56-63. 
    Abstract ( 1895 )   Save
    Data relay satellite(DRS) system can provide excellent services to various user spacecrafts,but the inter-orbit link(IOL)between DRS and user is obviously influenced by user's altitude.The effects of circular orbit spacecraft altitude on the performance of IOL were analyzed.A mathematical model was established to calculate the extreme values of free-space loss and DRS′s IOL antenna field angle,followed by simulation demonstrations with STK6.1.Based on the mathematical model,two instances of low earth circular orbit(LEO)spacecraft and navigation satellite were given respectively.For LEO users,the extreme Lf difference is less than 4dB and antenna field angle is within ±13° to which there is no need to pay attention during design,while for navigation satellite user,they are 15dB and larger than 35°which result that some relevant methods should be adopted to prevent over-design and antenna with large field angle should be employed on DRS.
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    Identification of Molecular Contaminant in Thermal Vacuum Test by Using GC/MS
    Jiao Zilong1 Pang Hewei2 Yi Zhong1 Yang Dongsheng1 Zang Weiguo1 Yu Qian1(1 Center of Assembly,Integration and Test,China Academy of Space Technology,Beijing 100094)(2 China Academy of Space Technology,Beijing,100094)
    2008, 28 (06):  64-67. 
    Abstract ( 1958 )   Save
    The contaminant collection and component identification tests were performed during the thermal vacuum tests.The witness plate was used to collect deposits,which was solved by acetone.The solution was analyzed by using GC/MS to identify compositions of the contaminants.Phthalate and siloxane were identified as the main contaminants in satellite thermal vacuum tests and solar array thermal vacuum tests.Possible source of methylphenylsiloxane in solar array thermal vacuum test may come from solar cell adhesive.
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