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25 August 1997, Volume 17 Issue 04 Previous Issue    Next Issue

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RESEARCH FOR APPROACHS OF DIFFERENCE GPS FOR PRECISION ANALYSIS OF RADAR MEASUREMENT SYSTEM Hu Shaolin Sun Guoji (System Engineering Institute of Xi'an Jiaotong University,Xi'an 710049) 1997, 17 (04):  .  Abstract ( 1663 )   Save In this paper,the possibility and data processing techniques for error analysis of tracking data and for radar precision judgement by the using difference GPS method are discussing.Assuming that there are a GPS signal receiver mounted in a radar station and a GPS signal transmitter loaded on a rocket,all of the error sources of GPS trackingdata are analysedin detail,and two additive models are built also.Based on two kinds of difference GPS algorillms suggested in this paper,a high precision location algorithm of carrier rocket is deduced.In order to separate all of the systemtic error residuals from total error and to analyse stochastic error of radar measuring data,a new and more essential concept “biasness”is advised,and a series of practical algorithms about stationary test are developed.When the indirect difference series are stationary,two rlbustresistant statistics are given to estimate the fixed bias errors If there exists any trendency error in the indirect difference,the best separation method and the resistant algorillm of residual analysis are given also.It can be shown that all of the statistics given in this paper are resistant against any kinds of outlying tracking data. Related Articles | Metrics

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SPACE DEBRIS NATURAL DECAY AND SOLAR ACTIVITY Liu Yaying (Purple Mountain Observatory,Academia Sinica,Nanjing 210008) 1997, 17 (04):  .  Abstract ( 1615 )   Save In this pepar have analysed and studied the variation of the debris population in low Earth orbit with the solar radiation flux F 10 7 .A calculation method to predict the long periodic variation of solar flux F 10 7 and a mathematics model to predict space debris population have been derived.The results show that:①The strong solar activity significantly accelerated the decay of satellites and debris in low Earth orbit.As a result,the yearly mean growth rates of the debris population decline;②The variation of the space debris population relates with ll year variation of the solar activity.The correlation coefficient reaches 0 9 during the 21th and 22st solar activity cycles from 1974 to 1994;③The space debris population increases with the launch rate.The debris having sizes of 10 cm or larger increase at about double the rate of growth of the cumulative launches; ④By 2020 the population of tracked objects(>10 cm in diameter)will reach 14500 when launch rates are fairly constant,being 114.264;⑤If untracked debris(1～10 cm in diameter)population will increase at about double the rate of growth of the trackable population,the space debris population will reaches 125000 by the year 2020. Related Articles | Metrics

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EXPERIMENTAL INVESTIGATION OF ARCJET ENGINE Wu Hanji Feng Xuezhang Liu Wenxi Zhang Zhiyuan Jiang Yuanda Pang Hongxun (Center for Space Science & Applied Research,Academia Sinica,Beijing 100080) 1997, 17 (04):  .  Abstract ( 1919 )   Save A laboratory system of low power(1 kW class)arcjet engine is described.It consists of a power supply and ignition system,propellant feeding system,engine body and some measurment devices. The performances described were acquired for different constrictor diameters(0 6～1 mm),mass flow rates(20～100 mg/s)and voltages(80～150 V)of power supply with Nitrogen and Argon.All of the tests were conducted in a 1 6 m long and 1 m in diameter vacuum chamber. Related Articles | Metrics

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BRIDGMAN GROWTH OF HgCdTe UNDER MICROGRAVITY IN SPACE Li Yijun Huang Liangfu Tan Xiaochen Zhang Zhongli He Ping Cui Weixin (Lanzhou Institute of Physics,Lanzhou 730000) 1997, 17 (04):  .  Abstract ( 1820 )   Save Bridgman crystal growth of HgTeCd was successfully finished under microgravity in space with the aid of a double heat zones crystal furnace piggyback on the Chinese returnable satellite.Some significant results were obtained.This paper introduces the design and the test process of the furnace,the main analyzed results of the recovered samples,as well as the discussion of the design of materials processing facilities and some related technological problems. Related Articles | Metrics

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THEORETICAL CALCULATION AND ANALYSIS OF SHOCK TEMPERATURE Tang Wenhui Zhang Ruoqi (National University of Defense Technology,Changsha 410073) 1997, 17 (04):  .  Abstract ( 1802 )   Save When a spacecraft under impact of debris,its shell will be shock heated.In this paper,three basic methods to calculate shock temperatures are described briefly.Shock temperatures for iron are calculated and the results are compared with those obtained from experiments.It shows that the results calculated by using three-term equation of state are in good agreement with the experimental results.In addition,the influence of several thermal physics parameters on the calculated value of shock temperature is discussed. Related Articles | Metrics

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SATELLITE CONSTELLATION DESIGN WITH INCLINED ORBITS PROVIDING MULTIPLE GLOBAL CONTINUOUS COVERAGE Yuan Shigeng (Beijing Institute of Spacecraft System Engineering,Beijing 100086) 1997, 17 (04):  .  Abstract ( 1730 )   Save More general inclined orbit and phased constellation of 180° nodal distribution which provides multiple global continuous coverage is investigated and designed using street of coverage technique.The article drives and presents necessary constraint conditions .The results of previous researches are improved. Related Articles | Metrics

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USING C-W EQUATION TO SOLVE ASTRONAUT EXTRA-VEHICLE TRACE She Mingsheng (Beijing Institute of Spacecraft System Engineering,Beijing 100086) 1997, 17 (04):  .  Abstract ( 2362 )   Save This paper discusses the application of the Clohessy-Wiltshine equation of spaceship relative motion dynamics to find its analytical solutions.We can rely on these solutions to study the motion track of an astronaut coming out of the spaceship.And these solutions can be applied to other conditions,such as the motion tracks of separated spaceships,the nelative motion tracks of a separated satellite and its launch vehicle,and the relative track of a projected object out off the spaceship. Related Articles | Metrics

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THE MOMENT METHOD’S STABILITY AND SUPERPOSITION ALGORITHM ON THE MULTI SCALE SUB DOMAIN FUNCTION BASS Yang Jisong (Xi'an Institude of Space Radio Technology,Xi'an 710000) Fu Junmei (Xi'an Jiaotong University,Xi'an 710049) 1997, 17 (04):  .  Abstract ( 1870 )   Save By compution of several practical examples,it is proved that the moment method's stability is very different for the different selection of bass function.So it is possible to improve the moment method's stability by select the appropriate bass function. Besides ,by selecting the multi scale sub domain bass function and superposition algorithm,the coefficient matrix's condition number can be reduced,so can be the requirement to the computer's memory.It is proved by several examples that the superposition algorithm for moment method's solution on the multi scale sub domain function bass is an effective and stable method. Related Articles | Metrics

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DISTRIBUTED PARAMETER MODEL FOR CALCULATING THE HEAT TRANSFER AND FLOWING PROCESS IN CPL EVAPORATOR Zhang Xuexue,Liu Jing,Zhang Chao (Tsinghua University,Beijing 100084) 1997, 17 (04):  .  Abstract ( 1623 )   Save A distributed parameter model is postulated to describe in detail the heat transfer and flowing process in the evaporator of Capalary Pumped Loop(CPL)system.Compared with the previously developed lumped parameter model,the present one gives the detailed temperature distribution of solid wall and vapor,the heat convection coefficient,the heat exchange coefficient in phase change and the thermal states of vapor along the axial distance of CPL evaporator,thus establishes a reasonable foundation for revealing in detail the heat transfer performance of CPL evaporator and further experimental study on its engineering model as well as for optimization. Related Articles | Metrics

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STUDY ON MODEL OF ATMOSPHERIC REFRACTION IN GPS MEASUREMENT Li Yanxing (First Crustal Deformation Monitoring Center,S.S.B.,Tianjin 300180) 1997, 17 (04):  .  Abstract ( 1626 )   Save The error of correction for atmospheric refraction is one of the biggest error sources in precise GPS measurement.Therefore,to study the theory of atmospheric refraction,establish the model which is more conformable to reality and derive the accurate formula for calculation corrections have become one of the most important tasks in the research of GPS measurement. Related Articles | Metrics