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    25 October 2010, Volume 30 Issue 5 Previous Issue    Next Issue
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    Critical Factors in Frequency Response Function Based Model Updating Using a Simulated Example
    DING Ji-Feng, HAN Zeng-Yao, PANG Shi-Wei
    2010, 30 (5):  1-8. 
    Abstract ( 2668 )   PDF (342KB) ( 2059 )   Save
        The basic theory of the frequency response function (FRF) based updating method was presented, and then the influences of the measured noise, the selection of frequency point and frequency band on the updating result were studied by using a simulated truss structure model. The conclusions show that:First, frequency selection is a key to the success of the updating, and appropriate selection of frequency point can decrease computational costs, improve the condition of the sensitivity matrix and resist the effect of measured noise; secondly, improving the accuracy of the measured data and increasing frequency band used in the updating are effective ways to get better updated model.
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    Beam Synchronization Strategy for DistributedInSAR Satellites Formation
    HE Dong-Lei, CAO Xi-Bin, MA Jun, LIU Pin-Xiong
    2010, 30 (5):  9-15. 
    Abstract ( 3197 )   PDF (204KB) ( 2083 )   Save
    Considering the demands of yaw steering for InSAR satellite formation, two beam synchronization strategies meeting the demands of yaw steering were put forward. In the first strategy, by combining the position relationship between satelliteground, and satellitesatellite and through coordinate transformation, SAR satellite′s attitude satisfying the demands of beam synchronization was programmed. However, the first strategy has shortcomings such as it is abstract to set up the model and tedious to solve the problem. Then, the second strategy based on Euler rotation was presented. Mathematical simulation shows that the two strategies can both effectively realize the beam synchronization, while the latter one is better.
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    On-orbit Maintainability System Design forManned Spacecraft
    WANG Da-Peng, TAN Chun-Lin, ZHANG Bai-Nan
    2010, 30 (5):  16-22. 
    Abstract ( 3861 )   PDF (287KB) ( 2223 )   Save
    On-orbit maintainability design is one of important design aspects of the manned spacecraft design, and related astronauts′ safety on orbit and the life and performance of the manned spacecrafts. Maintainability design philosophy was proposed based on the difference between on-orbit maintenance and ground maintenance. According to the maintainability design principles and engineering practice, the maintainability design framework, and the methods of establishing maintainability system parameter requirements, orbital replaceable units selection, and maintainability allocation and predication were completed for the manned spacecraft system design. The results provide a feasible approach to engineering implementation.
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    Thermal Deformation Release Analysis of Satellite′s Floating Design Method
    ZHANG Jing, BAI Shao-Jun, WEI Fei, ZHENG Gang-Tie
    2010, 30 (5):  23-30. 
    Abstract ( 3094 )   PDF (444KB) ( 1813 )   Save
    Floating design method (FDM) with high damping flexible connectors (HDFCs) aims at both releasing thermal deformation and attenuating vibration of the sensitive payloads during satellite in orbit phase, meanwhile, it can also prevent the reduction of structure strength. The effect on thermal deformation release of FDM was discussed. Based on the release theory of thermal stress by using FDM, the function of the flexible connections on structure′s thermal deformation was studied. And the thermal deformation of satellite structure, mainly the sensitive part, was analyzed and some design criteria was listed. Results show that FDM is quite effective on reducing payload′s thermal deformation, and its effect is greatly dependent on HDFC′s stiffness. Finally, the validity of the proposed analysis method was proved by numerical examples.
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    Parallel Imaging of MPI and Pthread Mixed Programming Based on Cluster
    TIAN Lei, FAN Shi-Ming
    2010, 30 (5):  31-38. 
    Abstract ( 4471 )   PDF (358KB) ( 2364 )   Save
    The mixed programming for Nonlinear Chirp Scaling (NCS) algorithm was designed according to the requirements of space borne Synthetic Aperture Radar (SAR) real time and near real time imaging. The two level pipelined parallel imaging of multiprocess and multithread with Message Passing Interface (MPI) and Pthread was researched and implemented on SMP cluster. Through the experiments on HP cluster, it is proved that the mixed program imaging algorithm can not only adapt to the instance that the time of one block of original echo data transferred from the front system is more than or equal to eight seconds, but also the instance that a great number of  original  echo data has been already accumulated.
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    Nonlinear and Compatibility Analysis on Satellite Navigation Modulation
    RAN Yi-Hang, HU Xiu-Lin, KE Ting, LIU Yu-Qi
    2010, 30 (5):  39-47. 
    Abstract ( 3778 )   PDF (375KB) ( 2714 )   Save
    The nonlinear characteristics and compatibility of minimum shift keying (MSK) and quadrature phase shift keying (QPSK) modulated signals were analyzed. Firstly, the timedomain and frequencydomain models of MSK modulated navigation signal were established and its impact on code pulse shape was discussed. It was suggested that MSK can be a candidate modulation for navigation signal. Secondly, nonlinear channel model was established, and the power loss, correlation loss, code tracking and spectrum separation coefficients of MSK and QPSK modulated navigation signals were simulated. Finally the simulation results show that the nonlinear performance and compatibility of MSK modulated navigation signals are better than QPSK modulated signals, ensuring the code tracking performance.
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    Spacecraft Control Method for Fast Attitude Maneuver and Stabilization
    LEI Yong-Jun, TAN Shu-Ping, LIU Yi-Wu
    2010, 30 (5):  48-53. 
    Abstract ( 3134 )   PDF (264KB) ( 1828 )   Save
    For the complex satellites with flexible appendages and input noises, the adaptive control method based on the characteristic model was used. A fast maneuver and stability controller was designed, which combined the multivariable track keeping control, logic integral control and logic differential control. A numerical simulation was presented. The simulation results show that the designed control method can insure the fast maneuver and stability performance.
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    Application of Electron Beam Modification Technique on Silicide Coatings
    YU Bin, JIN Qing-Chen, LIU Zhi-Dong, HE Jun
    2010, 30 (5):  54-55. 
    Abstract ( 2859 )   PDF (345KB) ( 1962 )   Save
    The silicide coating was prepared by fused slurry method with Nb521 alloy and re-melted by using high frequency electron beam. The morphology of specimen was analyzed by SEM and surface profiles equipment. It shows that, after electron beam re-melt process, the surface ceramic grain granularity and surface roughness decrease, the sintering effects between ceramic grains increase, and the obvious boundary appears between primary region and re-melted region. It proves that the energy distributing is well-proportioned, the high temperature oxidation resistance and shock testing validate capability are improved after electron beam remelting process.
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    Effect of AIT Environment on Properties of Satellite Thermal Control Coatings
    HU Tai-Bin, ZHANG Wei
    2010, 30 (5):  59-63. 
    Abstract ( 3175 )   PDF (221KB) ( 2422 )   Save
    Assembly integration and test (AIT) phase needs several months from spraying thermal control coatings to launching satellite. It is a question that whether the AIT environment affects the properties of thermal control coatings. The samples with the same ACR-1 thermal control coatings as the satellite antenna were put in AIT environment. The absorptivity and emissivity of the samples were measured for six times. The effects of temperature, humidity, and cleanliness on thermal control coatings were analyzed. The results show that the variations of the absorptivity and emissivity of ACR-1 thermal control coatings are small, which have little effect on the coatings′reliability. The cleanliness has more effect on thermal control coatings′absorpitivity than the other factors. So, the satellite environment needs a high cleanliness in AIT phase.
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    Passive Thermal Control Technologies of Exploration Instrument for Soft landing on Moon Surface
    MA Mian-Jun, HUO Hong-Qing, ZHANG Xiao-Qing
    2010, 30 (5):  64-68. 
    Abstract ( 2798 )   PDF (276KB) ( 1992 )   Save
    The heat transfer manner between the moon surface softlanding instruments and its exterior space environment was analyzed. The design and structure of the multilayer insulation blanket with lower equivalent emissivity were proposed, and the especial design of emissivity (ε) and solar absorptivity (αs) of the outermost radiant shield and its influences on the radiant equilibrium temperature were also discussed. Furthermore, taking advantage of lunar soil characteristics, the deployable outer multilayer insulation blanket can create a surface zone with the relative constant temperature equivalent to that of the lunar soil constant temperature layer. 
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    GPS Signal Application to Spacecraft Emergent Attitude Acquisition
    ZHANG Rong-Zhi, ZHOU Feng-Qi
    2010, 30 (5):  69-73. 
    Abstract ( 3002 )   PDF (230KB) ( 1927 )   Save
    Pseudo-range and phase measurement data received by onboard global positioning system (GPS) satellite receiver are broadly used in satellite orbit measurement. However, while GPS signals are received, the measurement auxiliary data signal strength (E) of receiving data  are received at the same time by the receiver. Theoretical analysis indicates that there is a strong correlation between the signal strength (E) of receiving data  and signal antenna angle α. If a strong correlation prior model between E and α is established, α can be calculated by E. In spacecraft missions, the relative positions of spacecraft and GPS satellites are known. The attitude of receiving antenna of onboard GPS satellite receiver can be calculated by three or more α of GPS satellite signal antenna during a fixed time. The accuracy of attitude determination is determined by the stability of the prior model. The observed and calculated data of the CHAMP satellite show that the accuracy for initial attitude determination is about 2°~3°. 
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    Analysis and Simulation of Adaptive Coding and Modulation forRemote Sensing Satellite Based on DVB-S2
    ZHANG Jia-Peng, HUANG Pu-Ming, CHEN Hong
    2010, 30 (5):  74-82. 
    Abstract ( 3083 )   PDF (436KB) ( 2096 )   Save
    The concept of adaptive data transmission, for the conventional remote sensing satellite data transmission was put forward. The adaptive coding and modulation (ACM) used in DVB-S2 was introduced. On the basis of DVB-S2 ACM, the application of adaptive coding and modulation in remote sensing satellite data transmission was analyzed. The results verify the adaptive system has much better performance than that of the non-adaptive system in the data transmission system through link budgets and SNR estimation. The transmission data quantity of adaptive system is 1.66 times than that of non-adaptive system through link budgets under the condition of fixed rainfall margins; while it is 8.14 times than that of non-adaptive system through SNR estimation based on the dynamic channel model. The factors impacting ACM performance were analyzed. The simulation results show that the SNR estimation error and delay have a great impact on system performance, and shifted thresholds technology can effectively reduce the impact of SNR estimation error on system performance, but it needs channel state prediction to reduce the impact of delay on system performance.
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