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    25 June 2011, Volume 31 Issue 3 Previous Issue    Next Issue
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    Orbit Determination for GEO Objects with Short Arcs ofSpaceBased Optical Observations
    LI Dong, YI Dong-Yun, CHENG Hong-Wei
    2011, 31 (3):  1-7.  doi: 10.3780.j.issn.1000-758X.2011.03.001
    Abstract ( 2705 )   PDF (423KB) ( 1968 )   Save
    Orbit determination for GEO objects using two short arcs from space based optical observations plays a key role in the space-based space surveillance systems. The significant information of a short arc was represented by an attributable including two angles and their time derivatives at the mean time. The admissible region was constructed to constrain the distance and the radial velocity between the surveillance satellite and the GEO object. Using the force equilibrium of a truss structure, the admissible region of the first arc was sampled by triangulation. The orbits of these samples were propagated to predict the attribute of the second arc. By comparing the predicted attribute with the actual one, several proper preliminary orbits were determined for orbit improvement. The simulation results show that our method can successfully achieve the least square solution and indicate the excellent convergence behavior.
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    Spacecraft Pure Star Navigation Method Based onGenetic Algorithm
    YANG Bo, LIU Ling-Ke, LIU Xiao-Xiao
    2011, 31 (3):  8-13.  doi: 10.3780/j.issn.1000-758X.2011.03.002
    Abstract ( 2393 )   PDF (338KB) ( 2073 )   Save
    A least square estimation method for determining spacecraft position in earthmoon transfer orbit was presented based on angle observations between three stars and two near celestial bodies. Due to relative low accuracy of the above method, the genetic algorithm was used to solve the spacecraft position equations based on the moon and stars celestial information observations and obtained a re-positioning of the spacecraft by using planetary sensors to measure the geometric relationship among the spacecraft, the moon, the earth, and using the star sensors to identify the stars. Simulation results show the method can greatly improve the navigation accuracy. 
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    Design and Application of Particle Filtering Algorithm Based on URTS Smoothing Proposal Distribution Function
    LI Bao-Li, GONG Yi-Song, GUI Qing-Ming
    2011, 31 (3):  14-19.  doi: 10.3780/j.issn.1000-758X.2011.03.003
    Abstract ( 10506 )   PDF (330KB) ( 1774 )   Save
    To improve the state estimate performance of the particle filtering with the Unscented Kalman filtering proposal distribution function, the Unscented Kalman filtering and the Rauch-Tung-Striebel (RTS) fixed interval smoothing algorithm were integrated, and a new kind of proposal distribution function named as Unscented RTS smoothing proposal distribution function was designed. The Unscented RTS smoothing distribution implements the Unscented Kalman filtering, and then carries out the RTS fixedinterval smoothing to produce a prediction sample. The accuracy of prediction particles is greatly improved by the new proposal distribution function, and the state estimation accuracy of the corresponding particle filtering method (PF-URTS) is also improved. The applications of the new particle filtering algorithm to the GPS/DR integrated navigation system will prove the feasibility and validity of  the proposed  method.
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    Spacecraft Relative Navigation Based on Improved Two Step Kalman Filtering
    LIU Yong, XU Shi-Jie, XU Peng, MA Jun
    2011, 31 (3):  20-25.  doi: 10.3780/j.issn.1000-758X.2011.03.004
    Abstract ( 2123 )   PDF (342KB) ( 1966 )   Save
    For the spacecraft relative navigation in the circular orbits, the linear Clohessy-Wiltshire(C-W) equations were used as the state equations, and the nonlinear equations for the relative distance and azimuth between two spacecraft were used as the observation equations. The improved two step Kalman filtering(TSF) was designed for the special relative navigation problem. The unscented transformation is used for determining the initial distribution about the state vector, and the intact form of the two step Kalman filtering was obtained. The simulation results validate the availability of this navigation method, and show that the TSF can provide better performance than extended Kalman filtering(EKF) and unscented Kalman filtering(UKF).
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    Rendezvous Orbit Design and Control of the Target Spacecraft
    LI Ge-Fei, SONG Jun, XIE Jian-Feng, HAN Chao, XU You-Fu
    2011, 31 (3):  26-34.  doi: 10.3780/j.issn.1000-758X.2011.03.005
    Abstract ( 2441 )   PDF (515KB) ( 1836 )   Save
    According to the target spacecraft′s orbit height and the chaser spacecraft′s orbit height, the design method of the target′s initial phase for the rendezvous orbit was presented. The mathematical models of the target′s rendezvous orbit control were established, which included the model of the coplanar phase and the model of the multi objective parameters to solve the target′s orbit phase, height and eccentricity. Based on the target′s phasing time analysis of orbit determination error, orbit control error and orbit prediction error, the strategy of the target′s phasing orbit maneuver was developed. Simulation results indicate that the target′s rendezvous orbit is obtained to meet the requirements of the objective orbit and the optimization principles of phasing control delta velocity is verified. Even the difference of the normal coplanar and the virtual coplanar is compared. The proposed model, control strategy and analysis methods are applicable to the target′s rendezvous orbit design and control implementation.
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    Critical Chain Project Management Model Based on Bayesian Networks
    SHANG Zhi
    2011, 31 (3):  35-42.  doi: 10.3780/j.issn.1000-758X.2011.03.006
    Abstract ( 2745 )   PDF (433KB) ( 1743 )   Save
    For the project schedule management problems, the critical chain project management Bayesian network model (CCPMBN) based on the critical chain project management and Bayesian network technologies was established. Firstly, the definition of CCPMBN was proposed and the nodes, edges and conditional probability distribution of nodes in CCPMBN were described in detail. Secondly, the critical chain procedure breakdown algorithm was demonstrated and the CCPMBN modeling method was established based on the critical chain. Thirdly, the resource conflict mode in critical chain and corresponding solutions were discussed. Finally, the basic properties and characteristics of CCPMBN verify its advantages in project schedule management.
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    Design and Simulation of Power System for Small Body Probe
    XU Hong-Ying, CUI Hu-Tao, CUI Ping-Yuan
    2011, 31 (3):  43-50.  doi: 10.3780/j.issn.1000-758X.2011.03.007
    Abstract ( 2406 )   PDF (515KB) ( 1702 )   Save
    The electrical power system of regulated and direct energy transfer was proposed, which was based on the problems of the power system of small body probe in the special deep space environment. According to the orbit characteristics of small body probe, the effects of environment factors and different loads on the electrical power system were analyzed and designed. The design of the electrical power system of the small body probe was based on energy balance, considering the relation between illumination and power. Finally, the design is demonstrated by numerical simulations.
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    Influence of Detector’s Pixel Size on Performance of Optical Detection System
    ZENG De-Xian, DU Xiao-Ping
    2011, 31 (3):  51-55.  doi: 10.3780/j.issn.1000-758X.2011.03.008
    Abstract ( 3179 )   PDF (266KB) ( 2326 )   Save
    In terms of optical detector construction and characteristic, the modulation transfer function (MTF) was selected as the system performance index, and MTF models were established. The influences of pixel size on the optical detector performance were analyzed by simulation. The results show that as the pixel size decreases, the image sensor MTF increases, while the optical system, defocus, image motion MTF decreases.
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    Optimal Design of Serial-parallel Viterbi Decoder with Multi-rate Convolutional Codes
    WANG Run-Xin, LIU Rong-Ke, ZHAO Ling
    2011, 31 (3):  56-61.  doi: 10.3780/j.issn.1000-758X.2011.03.009
    Abstract ( 1961 )   PDF (415KB) ( 1768 )   Save
    In order to reduce the hardware complexity, the structural characteristics of the Viterbi decoder were studied. The branch measure unit was optimized by analyzing the characteristics of convolutional codes. Result show that the calculated branch metric value reduces from 16 to 4. The parameters of trace back unit can be configured by the backtracking algorithm with high flexibility and speed. Besides, the multirate punctured convolutional codes of  CCSDS are acomplished by the same hardware architecture. 60% of the resources are saved compared with the normal serial-parallel structure with the same decoding speed. The throughput is as 8 times as the normal serial-parallel structure with the same hardware resources.
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    Preliminary Design and Characteristic Analysis of Moon-to-Earth Transfer Trajectories
    ZHANG Lei, YU Deng-Yun, ZHANG He
    2011, 31 (3):  62-70.  doi: 10.3780/j.issn.1000-758X.2011.03.010
    Abstract ( 2289 )   PDF (521KB) ( 1708 )   Save
    With the constraints of atmosphere reentry interface parameters and the landingpoint location,a method was proposed for the preliminary design of the moon-to-earth trajectory with direct atmosphere reentry. The method included two stages of iteration loops. The inner loop made moon-center orbit and earthcenter orbit continuous at the boundary of the moon influence sphere. To solve the earthcenter orbit parameters meeting the reentry angle constrain, a method combined Lambert problem and Newton-Raphson method was adopted. The outer loop made the moon-to-earth trajectory meet the landing-point location constrain by adjusting the launch time. The analysis shows that four types of moon-to-earth trajectories meet atmosphere reentry interface parameters. The four trajectories are descent-descent trajectory, descentascent trjectory, ascentdescent trajectory and ascentascent trajectory. Then the characteristics of the transfer trajectories were analyzed, such as the perigee geocentric distance, the transfer orbit insertion point distribution, the reentry point distribution. Simulation results indicate that the preliminary design method is effective.
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    New Fluxless Vacuum Soldering Process Using Plasma Cleaning in Power Modules
    CHEN Ya-Rong, HU Feng-Da, GAO Wei-Na, YANG Meng
    2011, 31 (3):  71-75.  doi: 10.3780/j.issn.1000-758X.2011.03.011
    Abstract ( 2482 )   PDF (329KB) ( 1684 )   Save
    In order to resolve the problems of low soldering efficiency and high void ratio in power modules, the solder type, vacuity and void ratio were investigated, and a new fluxless vacuum soldering process using plasma cleaning was presented. The results show that the vacuum pumping rate is increased and the void ratio is decreased obviously using solder sheet and plasma cleaning technology. The new soldering process with low void ratio, high efficiency and high quality conformance can be used in the soldering of high reliability power electronics.
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    An Adaptive Approach to Vision Measurement for Rendezvous and Docking with Non-cooperative Target in Space
    WANG Xiao-Liang, SHAO Xiao-Wei, GONG De-Ren, DUAN Deng-Ping
    2011, 31 (3):  76-83.  doi: 10.3780/j.issn.1000-758X.2011.03.012
    Abstract ( 2446 )   PDF (398KB) ( 1933 )   Save
    The mechanism of vision measurement for spatial non-cooperative target and extraction of feature points were analyzed. An improved filter was proposed for the unknown noise caused by feature points identification and the model uncertainty due to perturbations in space. The filter performance can be improved by estimating the magnitude of the measurement noise by using the update information and adaptive fading method for errors processing. A filter design for rendezvous and docking with non-cooperative target was also given which can provide estimation information of relative position, velocity, attitude angle and angular rate. Simulation results demonstrate that the proposed algorithm can achieve good results under conditions of unknown measurement noise and model error uncertainty.
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