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    25 December 2006, Volume 26 Issue 06 Previous Issue    Next Issue
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    Observability Analysis for Biased Satellites Autonomous Orbit Determination Systems
    Zhang Chunqing Liu Liangdong(Beijing Institute of Control Engineering,Beijing 100080)Li Yong(Research & Development Center,China Academy of Space Technology,Beijing 100094)
    2006, 26 (06):  1-7+13. 
    Abstract ( 1952 )   Save
    Concerning with the autonomous orbit determination for satellites with constant in the measurements of navigation sensors,it is a common approach to augment the system states with biased states and use Kalman filter,if the augmented system is completely observable.The(observability) of the proposed system was discussed using standard results of linear time-variant(systems) theory,and two very useful analysis results were presented.The results was demonstrated by numerical simulation.
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    Feature Extraction Algorithm for Spacecrafts Based-on Mathematical Morphology
    Li Kezhao Yuan Jianping Yue Xiaokui(Northwestern Polytechnical University,Xi'an 710072)
    2006, 26 (06):  8-13. 
    Abstract ( 1697 )   Save
    In the research of relative pose for spacecrafts based-on machine vision,the feature extraction algorithm was the basis of relative pose.A feature extraction algorithm for spacecrafts based-on mathematical morphology was proposed.Infused organically the attitude and orbit(information) of spacecrafts,structuring elements were reconstructed dynamically in feature(extraction) of this algorithm.The simulations show that this algorithm is a valid method to solve the problems of spacecrafts feature extraction.It is also especially valuable for the thought of structuring elements selecting dynamically to use in correlative research fields
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    Attitude Determination Algorithm Used by Lunar Satellite′s Imaging Sensor
    Wang Li Hao Yuncai(Beijing Institute of Control Engineering,Beijing 100080)
    2006, 26 (06):  14-17+41. 
    Abstract ( 1986 )   Save
    Ultraviolet lunar sensor is an imaging attitude sensor which has the wide FOV.(Aiming) at the attitude determination algorithm,analyzed the validity and limitation of the(conventional) circle algorithm used by MOSAIC Sensor.Pointed out that the geometric center of(lunar) image can't be regard as the nadir point in the low orbit.A new algorithm was developed throw the tailor equation based on the imaging analysis.The new algorithm can supply the high precise attitude data even in the low orbit.The simulation results prove this algorithm is valid.
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    Auto-Timing of Satellite Navigation System Using Conditional Estimate
    Xu Dongmei Yang Long(Academy of Equipment Command & Technology,Beijing 101416)
    2006, 26 (06):  18-23. 
    Abstract ( 1890 )   Save
    Capability of the active satellite navigation system is to estimate clock and(position) error autonomously.The capability is called as autonomous navigation.The algorithm of estimating the each satellite clock error was focused.Generally,in order to autonomous(navigating),each satellite makes pseudorange measurements to other visible satellites.Then these measurements are cross-linked to every satellites,so each can calculate every clock error.A new method of conditional estimating was introduced to calculate the clock error.The principle and(approach) of the method was discussed in detail.The synchronization error which was the difference between each estimated error was less than 0.4m(RMS).
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    Design and Experimental Investigation on a Flat Type Capillary Pumped Loop
    Liu Zhichun Liu Wei Zai Jun Yang Jinguo(Huazhong University of Science and Technology,Wuhan,430074)
    2006, 26 (06):  24-30. 
    Abstract ( 1812 )   Save
    Capillary pumped loop(CPL) which with a flat type evaporator and two flat type wicked condenser was designed,fabricated and tested to study operation character.Methane was used as working fluid,and the flat type heater was used as heating source.Experimental(investigation) results were presented.The results indicate that the heat transfer rates and(evaporation) rates are changed with the heating loads variation.At high enough heat levels,the(evaporator) dries out and the system fails.For a range of power applied to the evaporator,the(system) presented reliable start-ups and continuous operation for several hours.With as variable heat flow,the CPL evaporator presents good heat adaptability.With wicked condenser,the system pressure oscillation was reduced largely,even more eliminated.
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    Structure Description Based Image Compression Algorithm
    Jin Haiding Zhou Xiaokuan(School of Beijing University of Aeronautics and Astronautics,Beijing 100083)
    2006, 26 (06):  31-36. 
    Abstract ( 1721 )   Save
    Nowadays,wavelet based image compression algorithms are popular used in remote sensing image compression.The principle of wavelet based algorithms is to cut the high frequency information of image,therefore in the high compression ratio application,those methods may lose a lot of high frequency information of the remote sensing image.In order to reduce that distortion,a novel structure description based image compression algorithm was introduced,which had been proved to be superior to the SPIHT algorithm.
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    Thermal Uniformity Analysis for Heat Sink of Space Simulator
    Yu Tao Liu MinZou Dingzhong(China Academy of Space Technology,Beijing 100094)
    2006, 26 (06):  37-41. 
    Abstract ( 2020 )   Save
    Presented a typical heat sink in a space simulator with heat transfer model.(Compared) to other fin-structure radiators,heat sink for space simulator is characterized by looking into the enhancement of its thermal uniformity.Thus a detailed parametric study was performed by varying heat sink dimensions(fin length,fin thickness,and liquid nitrogen pipe radius) and(surrounding) conditions(liquid nitrogen velocity).It was found that thermal uniformity increased the most with the decrease of fin length,increase of fin thickness,and increase of liquid nitrogen pipe radius as well as the liquid nitrogen flowing velocity.At last,optimized heat sink parameter ranges were offered with help of numerical analysis results after(taking) some real design factors into consideration.
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    Primary Mirror Deployment Mechanisms for Space Optical Remote Sensors
    Liu ZhiquanSun Guopeng(China Academy of Space Technology,Beijing 100094)
    2006, 26 (06):  42-48. 
    Abstract ( 1760 )   Save
    The primary mirror deployment mechanism is one of the key parts of the deployable segmented imaging system which is utilized to realize large-aperture and ultra-high resolution for a space optical remote sensor.The basic classification of the primary mirror deployment mechanisms for space optical remote sensors was carried out.The structures,principles and characteristics of(different) primary mirror deployment mechanisms were analyzed.The development trends on(structures),actuators,deploying/locking devices and theoretical studies of future primary mirror(deployment) mechanisms were predicted.Key techniquesand the solutions for primary mirror(deployment) mechanisms were put forward.
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    Lambert's Problem in Spacecraft Rendezvous
    Zhu Renzhang~1 Meng Wei~2 Hu Xiting(1 Beijing University of Aeronautics and Astronautics,Beijing 100083)(2 China Academy of Space Technology,Beijing 100094)
    2006, 26 (06):  49-55. 
    Abstract ( 2248 )   Save
    Lambert's problem is studied for spacecraft rendezvous.Main geometrical properties of transfer orbit are interpreted.The Lagrange equation for transfer time was used to analyze the relationship between the transfer-time and orbital parameters.A graph method was presented to find the optimal transfer revolution;and the minimum-Δv,fixed-time,two-impulse rendezvous(between) two spacecraft orbiting along two coplanar unidirectional circular orbits were studied.For a given rendezvous time and an initial separation angle,optimal initial and termingal coasting periods can be found via a comparing-one-by-one method to obtain the globally minimum-Δv.
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    Satellite Attitude Determination with Modified Rodrigues Parameters without Gyro
    Yang Xiaohui Qin Yongyuan(Department of Automatic Control,Northwestern Polytechnical University,Xi'an 710072)
    2006, 26 (06):  56-61. 
    Abstract ( 2684 )   Save
    Analyzed and compared both MRP and quaternion algorithms' characteristics by (simulations).The satellite is equipped with CCD(Charge Coupled Devices) as the sole attitude (sensor) on board,and was disturbed by the first-order Markov force moment.Both MRP and (quaternion) algorithms were used to represent attitude,and UKF(Unscented Kalman Filter) was used to estimate the satellite's attitude and azimuth angles and angular rates.The computational burden of MRP is only half of currently used quaternion,while has better and less memory(consumption),because the quaternion standardization leads to singularity problem,but the MRP singularity problem is addressed by MRP switching.
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    Investigation on Start Performance of Scramjet Inlet
    Song Wenyan Ma Xiaofeng Liu Weixiong He Wei(School of power and energy,Northwestern Polytechnical University,Xi'an 710072)
    2006, 26 (06):  62-68. 
    Abstract ( 1930 )   Save
    A two-dimensional scramjet forebody/inlet of mixed external and internal(compression) with plane lip and wedged lip were designed by using constant shock intensity method.The effect of temperature and shock/boundary-layer interaction was considered in the design.The design and off-design performance and flow field of several types of designed forebody/inlet were calculated and compared.The comparison results indicate at lower flight speed,the starting(performance) and total pressure recovery coefficient of forebody/inlet with wedge lip is better than that with plane lip.At high flight speed,the forebody/inlet with plane lip is of high pressure ratio and lower cowl drag,the forebody/inlet with wedge lip is of high total pressure recovery coefficient and high cowl drag.Due to the problem of unsteady interaction between combustor and inlet,the effect of back pressure raise in combustor on inlet/isolator flow field and start performance was(simulated).The research results present at lower flight Mach number,it is easy for combustion-(induced) pressure waves to propagate upstream and even to result in inlet unstart.The pressure(disturbance) results from chemical energy release in the combustor.Isolator can prevent the(pressure) disturbance from influencing inlet in a certain extent and is helpful to combustion mode transition.The ability for preventing pressure disturbance to propagate upstream improves when flight Mach number is increased.For an unstarted inlet,the captured mass flow will decrease quickly.The decrease extent to the captured airflow at high flight Mach number is larger than that at low flight Mach number.
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