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25 June 2006, Volume 26 Issue 03 Previous Issue    Next Issue

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Filtering Algorithm and Simulation for Improving the Precision of the Satellites Autonomous Navigation Zhang Chunqing~1 Liu Liangdong~1 Li Yong~2(1 Beijing Institute of Control Engineering,Beijing 100080)(2 Research & Development Center,China Academy of Space Technology,Beijing 100094) 2006, 26 (03):  1-6+26.  Abstract ( 1901 )   Save How to precisely estimate and calibrate the systematic errors in the measurements is a key problem for improving the performance of autonomous navigation for satellites using(measurements) of the Earth,the Sun and the Moon.A two-step filter algorithm is designed and(applied) to estimate orbital parameters and identify the measurement biases simultaneously.(Simulation) results show that the 3-σ accuracies for position can be improved to the order of(300m) from the order of 10km using the filter algorithm presented. Related Articles | Metrics

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Research on Bi-satellite Positioning System Positioning Method Based on Distributed Pseudolite Pan Xiaogang Zhao Deyong Zhou Haiyin(National University of Defense Technology,Changsha 410073) 2006, 26 (03):  7-13.  Abstract ( 1804 )   Save Based on the deficiency of research on the Bi-satellites Positioning System(BPS)(using) pseudolite technology,an improved positioning strategy on BPS which is based on distributed pseudolite technology is pat forward.By taking full advantage of actual equipment of BPS and(restructuring) terrestrial calibration station to distributed pseudolite station,the strategy can carry out single positioning with data fusion method which do not change the actual mechanism of BPS.The improved strategy can ameliorate the GDOP of the system and heighten the location precision from the results of simulation experiment,especially in low latitude area,the location precision which is 20~60m can enhance more than three times of actual location precision,and the none-(resource) positioning mode can solve the limitation of user capability,coverability and anti-(vulnerability). Related Articles | Metrics

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Perturbation Analysis of the Relative Orbits of Formation Flying Satellite Huang Meili Xiang Kaiheng(China Academy of Space Technology,Beijing 100094) 2006, 26 (03):  14-19+37.  Abstract ( 2253 )   Save On secular flying of formation satellites,various perturbation factors may cause(relative) drifts to the satellites and prevent the flying mission form accomplishing.For LEO and MEO satellites,the relative drifts caused by perturbation factors are analyzed and the stability(conditions) for the formation configuration are derived.Furthermore,analysis of typical formations are carried out on the basis of stability conditions. Related Articles | Metrics

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Restriction of Spaceborne Multistatic InSAR Formation Configuration Design Huang Haifeng Zhu Jubo Liang Diannong(College of Electric Science and Engineering,National University of Defense Technology,Changsha 410073) 2006, 26 (03):  20-26.  Abstract ( 1999 )   Save The formation configuration design of distributed spaceborne interferometric SAR(DSInSAR) is key issue of system design.It must be combined with the flow of work and function of system.Because of its features of multisatic,squint angle and spacial baseline,spaceborne(multisatic) InSAR system must be analysed by new signal processing and performance evaluating methods.New restrictions of formation configuration design also must be put forward.Improved interferometric signal processing and performance evaluating methods are researched.Based on these new methods,restrictions of destance between master satellite and assistant satellites(formation),spacial baseline vector are presented.Distance restriction is based on analysis of bistatic radar SNR and time series.Spacial baseline vector restriction is based on analysis of DEM precision.Spacial baseline decorrelation which influence the interferometric phase error and DEM precision is analysed in detail.The quantitative and qualitative relation of spacial baseline vector,spacial(baseline) decorrelation,the intrferometric phase error and DEM precision is presented.Because(interferometric) Cartwheel and Pendulum formation is put forward based on side-glance geometry,simulation results show that the DEM performance of them are not optimal. Related Articles | Metrics

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Testing of Loop Heat Pipe with Dual-Evaporator Xiang Yanchao Li Jindong Zhang Jiaxun (China Academy of Space Technology,Beijing 100094) 2006, 26 (03):  27-31+43.  Abstract ( 1774 )   Save In order to investigate the performances of an loop heat pipe(LHP) with multi-(evaporator),an integrated experimental system including dual-evaporator loop heat pipe,parallel-flow condenser and equipment panel was established,which could accumulate,transfer and radiate heat.An extensive testing program was conducted on a loop heat pipe with two evaporators.The tests(results) showed that the loop could be always started successfully if the loop started up in(sequence),which was the most dependable start-up model.After multi-evaporator loop started up,only one Compensation Chamber contained two-phase fluid and control the loop operating(temperature) under the variable conductance mode.The heat loads distribution was a function of the loop(operating) temperature.However,under constant conductance mode,all Compensation Chambers were liquid filled and the heat loads distribution between evaporators had hardly any effect on the loop operating temperature. Related Articles | Metrics

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Coverage Optimization of Multimedia Communication Satellite on Mainland China Tang Jinfei Yan Zhongwen(China Academy of Space Technology,Beijing 100094) 2006, 26 (03):  32-37.  Abstract ( 2014 )   Save Beam coverage and coloring scheme is the premise of multi-beam communication(research).As part of a research project,a solution to hexagonal coverage and coloring problem for mainland China is presented.Based on the hexagonal model analysis and with the aid of MATLAB map data and functions,a coverage solution algorithm is derived and applied to the problem.(Optimized) coverage and coloring is obtained by the algorithm.Finally future research area in this problem is outlined. Related Articles | Metrics

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Calculation Method of a Kind of Near-round Repeating Satellite Orbit Using Nadir Points Duan Fang Liu Jianye(Navigation Research Center,Nanjing University of Aeronautics and Astronautics,Nanjing 210016) 2006, 26 (03):  38-43.  Abstract ( 1786 )   Save A method of nearly-round repeating orbit designing is proposed.It's aimed to resolve the question of orbit designing with the restriction of a specific satellite ground trace.The(relationship) between the satellite ground trace and orbit parameters is analyzed.It's concluded that the designing of the nearly-round repeating orbit with the restriction of a specific satellite ground trace relies on the determination of the semi-axis and the inclination.Non-linear equations are(constructed) with the restriction of the satellite ground trace to resolve the unknown semi-axis and inclination,but it's too complicated to be resolved directly.Therefore,an iteration algorithm is used to resolve it.A MATLAB program is built to realize the algorithm.The result is simulated by STK(Satellite Tool Kit).It shows,this algorithm works well in obtaining the designing target. Related Articles | Metrics

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Novel Double-Ring Antenna with Broad Bandwidth Wide Beam and Circular Polarization Dong Tao Guo Wenjia(Satellite Application System Department,China Academy of Space Technology,Beijing 100080) 2006, 26 (03):  44-46+58.  Abstract ( 2258 )   Save Antenna with broad bandwidth,wide beam and circular polarization performance are needed in spaceborne,airborne and terrestrial application.A novel double-ring antenna is(presented).The structure of this antenna is also very simple.The measurement of radiation(characteristics) is in good agreement with simulation results.The gain of low elevation angle can be improved by adding a metallic reflector,and the input impedance and the axis ratio can also be(improved). Related Articles | Metrics

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Application Study on Humidity Control Technique for the Pressurized Module in Satellites Zhang Jiaxun Li Jindong(China Academy of Space Technology,Beijing 100094)Sun Yaochi(Lanzhou Physics Research Institute,Lanzhou 730000) 2006, 26 (03):  47-51.  Abstract ( 1919 )   Save In order to solve the humidity requirements of the camera in the satellite,the(application) study on the humidity control technique for the pressurized module is conducted by(experimental) verification and thermodynamic analysis.By the thermal test and in-orbit test of the satellite,it can be got that,by using the moisture of the camera's film,using humidity control(subsystem) and conducting humidity adjustment before launch,the relative humidity of the local area in the pressurized module of the satellite can be controlled in a range about 30%~60%,which meets the requirements of the camera.It is concluded from the paper that,the humidity control technique used by the thermal control system is successful,and ensure the full success of the(satellite's) task. Related Articles | Metrics

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Optimization Design Approach of Formation Flying for Distributed Spaceborne SAR Super-resolution Imaging Ran Chengqi(National University of Defense Technology,Information System and Management College,Changsha 410073) 2006, 26 (03):  52-58.  Abstract ( 1937 )   Save The formation configuration design of distributed satellite system is a key issue of(system) design.For the spaceborne parasitical synthetic aperture radar(SAR) which fulfills super-resolution imaging,a generalized approach of formation configuration design is presented from the point of system performance optimization.It is generalized as an optimal problem.The objective function is setted up,based on analyzing system mission.By using baseline vector as intermedium,the relationship of objective function and satellite orbit root is established.A genetic algorithm is used to solve the optimal problem.Formation systems with different number satellite are simulated by the optimal design approach.And system performances of them arecompared with those of(interferometric) Cartwheel and Pendulum.The simulation result provescorrectness and validityof the optimal method. Related Articles | Metrics

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Spot Beam Judgement Algorithm of Low Earth Orbit Satellite Mobile System Liu Yanjing~1 Liu Gang~2 Wu Shiqi~1(1 National Key Laboratory of Communication,UEST of China,Chengdu 610054)(2 Chengdu R & D Institute of ZTE Corporation Ltd,Chengdu 610041) 2006, 26 (03):  59-66.  Abstract ( 2042 )   Save According to the space geometry,the coverage of satellite constellation on earth,and the shape of spot beam,by building up mathematic model,a spot beam judgement simulation(algorithm) is proposed.Based on the typical LEO system-Globalstear,it is simulated and gets(reasonable) results,which is similar to real system parameters and improves the algorithm Related Articles | Metrics

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Consideration of the Determination of Space Service Polarizations Gao Xiaoyang(China Satellite Telecommunications Corporation,Beijing 100083) 2006, 26 (03):  67-71.  Abstract ( 1837 )   Save By reviewing the progress of the modifications of the Planned BSS in the World (Radiocommunication) Conference and based on detailed transmission analysis,it is emphasized to considerthe various factors in the determination of space service polarizations,such as carrier transmission characteristics in defferent polarizations,combined space service applications,the(provisions) in the Planned BSS and the convenience of both spectrum coordination and the installation of the receiving equipment. Related Articles | Metrics