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25 October 2008, Volume 28 Issue 05 Previous Issue    Next Issue

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Principle of Deep Space Autonomous Navigation Based on X-ray Pulsars Zheng Wei Sun Shouming Tang Guojian(College of Aerospace and Material Engineering,National University of Defense Technology,Changsha 410073) 2008, 28 (05):  1-6.  Abstract ( 1822 )   Save The autonomous navigation is the key technology to realize the interplanetary exploration,the principle of navigation based on X-ray pulsars is steady,credible and high-precision which is free from the limits of the near earth space and provides a new thought to the autonomous navigation.The navigation principle based on the X-ray pulsars was studied,the algorithm of predicting TOA and the method of solving the ambiguity points were put forward,and the method of estimating the position based on the Least Square theory was studied.The results show that,with 0.001 arcsec accuracy of pulsar direction and 1μs accuracy of the time of pulse arrival,the position accuracy can reach 10km during the 140 days' flight and the navigation accuracy is not sensitive to the initial error,autonomous navigation based on X-ray pulsars can satisfy the requirements of interplanetary exploration. Related Articles | Metrics

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Control Laws for Autonomous Proximity with Non-cooperative Target Lu Shan Xu Shijie(School of Astronautics,Beijing University of Aeronautics and Astronautics,Beijing 100083) 2008, 28 (05):  7-12.  Abstract ( 1808 )   Save Two control laws for autonomous rendezvous and interception with non-cooperative target were designed using Lyapunov approach.First a control law for autonomous rendezvous was derived according to the nonlinear relative motion dynamics.Then the control law was improved in order to apply to the interception mode,which could ensure the chaser approaches the target at a certain relative velocity.Meanwhile considering the maneuver of the non-cooperative target,a new control law for autonomous proximity was derived using Lyapunov min-max approach.The simulation results validate the availability of control laws for autonomous proximity based on Lyapunov approach. Related Articles | Metrics

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Orbital and Attitude Cooperative Control of Small Satellite in Proximity Operation Zhang Yanzhao Yuan Jianping Luo Jianjun Zhou Wenyong(College of Astronautics,Northwestern Polytechnical University,Xi'an 710072) 2008, 28 (05):  13-19.  Abstract ( 1933 )   Save Positional and attitude error dynamics model of small satellite relative to a target satellite was derived,then the desired relative orbit and desired attitude of small satellite were designed.Orbital and attitude cooperative control strategy was used and the parametric uncertainty of small satellite was considered.An adaptive full-state feedback controller was designed.Numerical simulation shows the controller is adaptive well. Related Articles | Metrics

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Analyses of Constellation Area Navigation Capacity and Key-Satellite Zhu Sha Wang Hongqiang Li Xiang Mao Junjie(School of Electronic Science and Engineering,National University of Defense Technology,Changsha 410073) 2008, 28 (05):  20-24+65.  Abstract ( 1877 )   Save Area navigation capacity is an important parameter for evaluating navigation performance of constellation.The evaluation indexes of area navigation capability were presented,including standard deviation of geometry dilute of precision and variability of geometry dilute of precision from geometry dilute of precision,and the key-satellite of the navigation constellation was analyzed based on the indexes.The two indexes and area average geometry dilute of precision describe the area navigation capability in different ways.The indexes can fulfill different applications for determining the key-satellite of constellation for area navigation.The correlations between these indexes insure that the key-satellite is the same one in most cases. Related Articles | Metrics

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Study of Influence Factors of Ground Ventilation and Heat Exchange Performance of Drawer Standard Chassis Han Haiying1 Jiang Jun1 Cao Jianfeng1 Liu Qiang2(1 China Academy of Space Technology,Beijing 100094)(2 China Aerospace Science & Technology Corporation,Beijing 100830) 2008, 28 (05):  25-31.  Abstract ( 1995 )   Save The ventilation and heat exchange performance of Drawer Standard Chassis in two type inlet and outlet modes were tested and simulated.The influence of inlet flux and width of ventilation hole and nature convection on heat exchange performance of standard chassis was studied.The test results show that,increasing inlet flux and decreasing width of ventilation hole within a scale are main ways to improve the heat exchange performance of standard chassis.Moreover,because heat exchange performance of standard chassis in orbit is better than or same with that in ground at the same states,design parameters which meet heat exchange demand in ground would also satisfy to the requirement of orbit operation. Related Articles | Metrics

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Dynamic Channel Assignment Arithmetic Based on Evolutionary Arithmetic Yan Zhongwen1,2 Bu Tian1 Zhang Naitong1(1 Communication Research Center of Harbin Institute of Technology,Harbin 150001)(2 China Academy of Space Technology,Beijing 100094) 2008, 28 (05):  32-38.  Abstract ( 2040 )   Save Because of the long transmission delay for GEO communication satellites,the performance of dynamic channel assignment(DCA) is sensitive to the time of DCA algorithm.A mathematical model was firstly established for DCA of a new generation of broad-band multimedia communication satellite.Then,a novel approach for DCA based on evolutionary arithmetic(EA) was proposed.The simulation results demonstrate that this EA method reduce the system delay 47% and offer more efficient channel assignment strategy than that of the classic method. Related Articles | Metrics

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Explicit and Implicit Calibration for In-flight Spacecraft Gyroscope Ni Xinguo Yang Huabo Zhang Shifeng(College of Aerospace and Material Engineering,National University of Defense Technology,Changsha 410073) 2008, 28 (05):  39-45.  Abstract ( 2015 )   Save The explicit and implicit calibration approaches for spacecraft gyros were introduced.The dynamic equation and measurement equation of explicit and implicit approaches were set up,and estimation of calibration parameters was obtained by extended Kalman filter.In particular,the two approaches applied to in-flight spacecraft gyro calibration were compared.The result simulation shows that the performances of the two approaches are basically comparable,and relative accuracy is less than 10%.Sensitivity tests indicate that the explicit filter results are essentially insensitive to variations in given spacecraft dynamics model parameters,but explicit filter implements were easily. Related Articles | Metrics

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Grouped Truncate PN Code Based Channel Estimation Method for SOFDM Symbols in Satellite Communication Yang Tong(China Academy of Space Technology,Beijing 100094) 2008, 28 (05):  46-53.  Abstract ( 1911 )   Save The channel estimation method that based on the PN sequence is generally characterized by a concise computational process and a lower computational complexity,which has been already applied in the terrestrial WLAN system.While adopting such means for estimating SOFDM symbols in satellite communication,there comes a problem that the multipath delay is much longer than the period of SOFDM symbol,which makes the traditional measure failed and the estimate precision lost.Therefore,an improved method was proposed,which divided the data frame into several fixed groups by considering that the channel characteristics was approximately cycled with a periodicity which was related to the RMS value of multipath delay.Afterwards,the long PN sequence was designed to be truncated to many short PN codes in order to track the partial changes of the channel,thus their channel response value(CRV) could be estimated respectively.The experimental results prove that it is able to estimate data symbols' CRVs with a higher accuracy and improve the estimate precision by at least 10 times paralleling to that of other ordinary methods. Related Articles | Metrics

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Research on GPS L5 Signal Acquisition Method Zhang Lu Zhang Qingjun(The System Design Department of China Academy of Space Technology,Beijing 100094) 2008, 28 (05):  54-58+71.  Abstract ( 1967 )   Save L5 signal is a new civil navigation signal adopted by Global Position System since it has better navigation performance because of higher code rate and longer code length.The traditional acquisition method results in long acquisition time,especially under high dynamic circumstance on board,so a matched filter combined with FFT acquisition method was proposed,which could search the code phase and Doppler frequency at the same time,therefore reduced the acquisition time.The theoretical analysis and simulation results show that,this acquisition method is suitable to long code in large Doppler offset situation.Based on the comparison among various subsection methods,an appropriate subsection method which could satisfy the acquisition demand of L5 signal in GPS system was chosen.Finally,the acquisition experiment was implemented using a FPGA,tests were then conducted to verify and validate the method. Related Articles | Metrics

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Research on Identification and Parameter Estimation of Cratering Induced by Impact on Single Plate with Acoustic Emission Signals Tang Qi1 Pang Baojun1 Han Zengyao2 Liu Wugang3(1 School of Astronautics,Harbin Institute of Technology,Harbin 150080)(2 China Academy of Space Technology,Beijing 100094)(3 Beijing Institute of Structure and Environment Engineering,Beijing 100076) 2008, 28 (05):  59-65.  Abstract ( 1978 )   Save Due to the threat of impact to spacecraft from space debris,the space debris in-suit detection system is required.For developing the detection system based on acoustic emission(AE) technique,means of failure mode identification by AE signals from hypervelocity impact on protection structure is necessary.AE waves were obtained with experiments of hypervelocity impact on single plate and numerical simulations and were analyzed in time domain and frequency domain.The results indicate that the main trough value increases linearly with the increase of impact velocity till the plate is penetrated.A threshold value that divides the penetration and cratering in the failure modes of plates can be defined on the ratio of high frequency component amplitude to low frequency one.A method was presented which identifies cratering mode of single-sheet plate and estimates the impact velocity and size of crater assuming certain diameter of projectile. Related Articles | Metrics

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Effect of Midnight Solar Intrusion on Temperature of Second Mirror Assembly of FY-4 Radiometer Liu Zhenyu1 Cheng Huier1 Sun Jingliang2(1 Institute of Engineering Thermophysics,Shanghai Jiaotong University,Shanghai 200240)(2 Shanghai Academy of Spaceflight Technology,Shanghai 200235) 2008, 28 (05):  66-71.  Abstract ( 1862 )   Save The thermal calculating model of radiometer on the meteorological satellite FY-4 was established and temperature variations of the second mirror assembly were calculated by I-DEAS/TMG software.The effect of midnight solar intrusion on the temperature of the second mirror assembly was investigated.The calculation results show the highest temperature of the second mirror occurs during the period of local midnight when the solar declination is 0°or 23.45°.When the solar declination is 8.8°,the midnight solar intrusion has more effects on the temperature of the spider and housing of second mirror assembly than that of any other period. Related Articles | Metrics