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25 October 2015, Volume 35 Issue 5 Previous Issue    Next Issue

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BDS Satellite Real Time Orbit and Clock Determination and Initial Results Analysis CUI Hong-Zheng, TANG Ge-Shi, SONG Bai-Yan, LIU Hui-Cui, GE Mao-Rong 2015, 35 (5):  1-7.  doi: 10.3780/j.issn.1000-758X.2015.05.001 Abstract ( 939 )   PDF (3796KB) ( 1375 )   Save Navigation satellite real time orbit determination and clock determination are research highlights in navigation areas. The processing strategies and processes for Beidou Navigation Satellite System (BDS) real time orbit determination and clock determination were provided，especially for the clock processing with zero-differenced absolute clock and epoch-differenced relative clock. Using the data from the Multi-GNSS Experiment (MGEX) and international GNSS monitoring & Assessment Service (iGMAS) tracking networks，the average orbit accuracy for real time BDS in radial direction is better than 20cm，and 10cm for GEO，IGSO and MEO，respectively. And the clock accuracy for real time BDS can reach 0.5~4.5 ns，and 0.2~2.0 ns for GEO，IGSO and MEO，respectively. Based on the this result，the real time precise pointing position (PPP) performance following BDS can achieve decimeter level. Related Articles | Metrics

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Ranging Error Caused by MAI in Terrestrial Pseudolites System and its Correction Method HE Cheng-Long, YU Bao-Guo 2015, 35 (5):  8-14.  doi: 10.3780/j.issn.1000-758X.2015.05.002 Abstract ( 725 )   PDF (3551KB) ( 765 )   Save The terrestrial pseudolites system is easy to realize high accuracy positioning comparing with the low transmit error in lineofsight propagation link, while it has approximate constant ranging error under its multiaccess interferenc(MAI) for all terrestrial pseudolites having constant positions. A correction method based on feedbackSIC (Serial Interference Cancellation)was given. First the receiver decide whether it is in strong nearfar effect area based on ranging and coarse positioning data; then restrain the interference of strong pseudolites′ signals on needed signals′ ranging by SIC; a feedback structure was adopted to enhance the cancellation performance. The simulation and hardware test results show that the method has an effective ranging correction performance which could reduce the error from tens of meters to 0.3 m in certain environment with high near-far effect. Related Articles | Metrics

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Zero Reaction Motion Trajectory Tracking for Space Manipulator with Non-zero Initial Momentum LIAO Zhi-Xiang, SHI Peng, ZHAO Yu-Shan, ZHENG Han-Qing 2015, 35 (5):  15-21.  doi: 10.3780/j.issn.1000-758X.2015.05.003 Abstract ( 827 )   PDF (3556KB) ( 519 )   Save The free-floating manipulator system with non-zero initial momentum was studied.The configuration parameters of the manipulator system and the Lagrange equations were used to build the dynamic model.  In order to eliminate the coupling effects between the base and the manipulators in angular velocity,the zero reaction motion equation was derived by using the manipulator system redundancy. A polynomial interpolation method was used to approach the trajectory of end-effector and the trajectory was planned due to the initial and final position of end-effector which could turn workspace of end effector into joints space. A suitable proportion-differentiation (PD) control algorithm was designed to drive manipulators movement. Simulation results demonstrate that the end-effector can smoothly track the target and the movement of the manipulator doesn′t make any disturbance to the base′s attitude at the same time and the spacecraft also can work normally because of the stability of base. Related Articles | Metrics

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Minimum Fuel Control of Relative Ellipse Semi-Minor Axis in Micro/nano-Satellite In-Plane Companion-Flying ZHOU Mei-Jiang, WU Hui-Ying, QI Jin-Ling 2015, 35 (5):  22-32.  doi: 10.3780/j.issn.1000-758X.2015.05.004 Abstract ( 921 )   PDF (5904KB) ( 550 )   Save It is essential to save fuel in orbit control for micro/nano satellite due to the lack of resources. The  influences of control direction and control time on the relative ellipse semi-minor axis in in-plane companion-flying satellites were studied based on the Hill equation. Both theoretical analysis and simulation results show that the most efficient control method of relative ellipse semi-minor axis is to impose control parallel to the lateral direction on the top or bottom points while the control quantity |ΔV|≤nb/2 is certain and the relative ellipse semi-minor axis will change |Δb|=2|ΔV|/n at the same time. Related Articles | Metrics

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Analysis of Influence of South Atlantic Anomaly Based on Space-based Visible Detection Images ZHANG Ke-Ke, LI Zong-Yao, HU Hai-Ying, ZHU Zhen-Cai, YANG Gen-Qing 2015, 35 (5):  33-40.  doi: 10.3780/j.issn.1000-758X.2015.05.005 Abstract ( 733 )   PDF (6170KB) ( 601 )   Save When the in-orbit high sensitivity detection visible sensor passes through the south Atlantic anomaly（SAA）region，its detection capability is weaken and unable to identify the target. Based on the space-based visible detection images collected by the satellites in SAA，the principle of anomalies was analyzed. And a evaluation method of SAA area influence was developed，based on the image character change of CCD detector in dark pixel areas. According to the statistics and analysis of the dark pixel areas image character parameters，such as mean，standard deviation，hot pixel and living pixel number，et al. The inflexion of continuous images occurring significant influence was estimated. The multiplication curve fitting was used to compute the spatial distribution and border of SAA area. Then a simple method was proposed to measure the SAA border, which has a significant influence on the operating satellites in this orbit altitude. Finally, to avoid the SAA area influence on high sensitivity detection satellite, the improvement measures and recommendations were given according to the analysis results. The data analysis and evaluation method will provide the foundation for future work on space debris detection. Related Articles | Metrics

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Numerical Simulation on Vertical Water Entry Impact of a Recovery Module LI Shao-Wei, QU Qiu-Lin, LIU Pei-Qing, ZHOU Dan-Jie 2015, 35 (5):  41-49.  doi: 10.3780/j.issn.1000-758X.2015.05.006 Abstract ( 832 )   PDF (4974KB) ( 452 )   Save The complex multiphase and fluid-structure interaction problem of the vertical water entry of a recovery module was numerically researched. The two-dimensional axisymmetrical unsteady Reynolds averaged Navier-Stokes(URANS) equation and Realizable k-ε turbulent equations were solved by the SIMPLE algorithm. The water impact on the recovery module in single-degree-of-freedom motion was simulated by dynamic mesh method. The air-water interface was tracked using the volume of fluid (VOF) model. The employed numerical methods were firstly validated by comparing simulation results with experimental data. The effects of slamming velocity and weight on slamming force were investigated. A relationship formula of the acceleration peak to variable velocities and weights was obtained. The maximum shock pressure on the recovery module occurred in the early stage when entrying into the water and the pressure peak is always located in the splash root close to the recovery module. Related Articles | Metrics

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Research on Passive Control Dynamics of Micro-vibration Based on Harmonic Balance Method ZHU En-Yong, WEI Chuan-Feng 2015, 35 (5):  50-55，63.  doi: 10.3780/j.issn.1000-758X.2015.05.007 Abstract ( 966 )   PDF (3243KB) ( 508 )   Save For investigating the effects of passive vibration isolator parameters on the vibration transmissibility, nonlinear stiffness characteristics of the vibration isolating material was described by the cubic polynomial function of its deformation, and the nonlinear damping was characterized by viscoelastic fractional derivative operator. The nonlinear dynamic model in microgravity environment of passive vibration isolator system was developed．The dynamic response characteristics were analyzed by the harmonic balance method, and the vibration transmissibility was obtained. Then the influence of stiffness, damping and mass of the isolator and isolated body on vibration isolation effect were analyzed．The results provide theoretic reference for design of spacecraft isolators．The results show that the effects of vibration isolator nonlinear damping coefficient on vibration transmissibility were obvious and the effects of vibration isolation object mass on resonance vibration peak value have a great deal to do with the vibration isolator nonlinear damping coefficient. Related Articles | Metrics

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Ground High Voltage Suspension Theory and Applications for Electrostatic Accelerometer CHEN Guang-Feng, HUO Hong-Qing, WANG Zuo-Lei, YIN Dong-Dong, LEI Jun-Gang, ZHANG Xiao-Qing, XI Dong-Xue 2015, 35 (5):  56-63.  doi: 10.3780/j.issn.1000-758X.2015.05.008 Abstract ( 917 )   PDF (4194KB) ( 956 )   Save The electrostatic suspension accelerometer is a quasi steady and non gravity precision measurement equipment for spacecraft. In the development of electrostatic suspension accelerometer, the evaluation of the functions and the performances of the accelerometer need to be accomplished by the high voltage suspension. On the ground tests, the theoretical analysis of the   electrostatic suspension accelerometer related issues involved in the high voltage suspension was carried out. The ground suspension principle, a high voltage circuit, chooses the working point, control stability, and the high voltage static electricity effect analysis etc.were given. The system resolution near the 0.1Hz is about 10-8g/Hz1/2 on ground test, and can finish the function and related performance tests in the suspension state.The main factors of the direct performance evaluation of the electrostatic suspended accelerometer on ground were obtained, and the related problems were discussed. Related Articles | Metrics

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Radiometric Calibration and Accuracy Analysis based on Spaceborne SAR TAO Man-Yi, JI Peng, HUANG Yuan-Bao, JIANG Yan 2015, 35 (5):  64-70.  doi: 10.3780/j.issn.1000-758X.2015.05.009 Abstract ( 1065 )   PDF (3082KB) ( 1168 )   Save With the development of spaceborne synthetic aperture radar(SAR)application,the radiometric calibration technology was used to observe objects′ physical characters.    Because the radiometric calibration technology is very complex,on the study of radiometric calibration and accuracy analysis will be mostly focused in the strip mode with single channel and single polarization.Firstly,the radar equation was derivated,then with the measured calibration constant,the short-term and long-term relative calibrations were studied based on an error model and formula. At the same time,the influence of calibration constant for absolute radiometric precision was analyzed and the system correct was finished.Finally the validated result on TerraSAR-X satellite shows that the difference of the calculated value and the measured one is less than 0.05dB. Related Articles | Metrics

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An Efficient Encoding and Decoding Algorithm Suitable for Satellite Data Translation ZHANG Ya-Hang, CHENG Bo-Wen 2015, 35 (5):  71-76.  doi: 10.3780/j.issn.1000-758X.2015.05.010 Abstract ( 615 )   PDF (2789KB) ( 502 )   Save A time efficient fountain error correcting codes called rapid raptor codes (RRC) was presented,which was better than the traditional raptor codes while maintaining the same symbol recoverable performance. Compared with the original raptor code, intermediate symbol and repair symbol generation were combined into one step in encoding process, and the conception of degrees of symbols from the belief-propagation （BP） decoder was imported in decoding process before Gaussian elimination decoding with a much smaller matrix size. The improved algorithm is much simple and has better time efficient, therefore suitable for satellite application layer data translation, memory protection and deep space message translation. Related Articles | Metrics

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Satellite-ground Integrated Communication Network Based on Distributed Data Center GUO Jia-Ning, LI Chang-De, SHI Yun, WU Bin 2015, 35 (5):  77-84.  doi: 10.3780/j.issn.1000-758X.2015.05.011 Abstract ( 776 )   PDF (3683KB) ( 564 )   Save The satellite-ground integrated communication network usually has the characteristics of wide coverage and large amount of data transmission. Current studies concentrate on transmission protocols and resource management. Due to the weak computing power of the satellite network, an integrated satellite-ground communication network with a distributed data center merged with the backbone optical network was proposed which can realize logic link and optical transmission for different component sets in the data center. The satellites were taken as special nodes in the integrated network. And multiple factors were taken into account, such as the cost of internal transfer and external request, to optimize the network architecture by using the integer linear programming (ILP) based on Chinese telecom network. Simulation results show that the proposed network architecture and the optimization technique can solve network design and resource optimization problems well in the integrated network. It also provides a competitive platform for large-scale data transmission and processing. Related Articles | Metrics