Table of Content

    15 May 2006, Volume 26 Issue 3 Previous Issue    Next Issue
    An Observation-Based Model of Solar Wind Background
    XIANG Changqing;FENG Xueshang;FAN Quanlin;YAO Jiusheng
    2006, 26 (3):  161-166.  doi: 10.11728/cjss2006.03.161
    Abstract ( 1998 )   PDF (2609KB) ( 1347 )   Save
    Photospheric magnetic field measurements and coronal polarized brightness observations are used as constrains to develop a single-fluid solar wind background model, which includes proton density, bulk velocity and magnetic field. Proton temperature will be dealed with in further studies, The synoptic maps of K-corona polarized Brightness (pB) at 1.36 solar radii observed by MKIII in High Altitude Observator (HAO) are applied to derive corona density according to the solar wind density model constructed by Guhathakurta in 1996. In order to determine the global magnetic field, the synoptic maps of photospheric magnetic field in Wilcox Solar Observatory (WSO) are adopted to be the bottom boundary condition of the model of horizontal current and current sheet (HCCS) established by Zhao in 1994. Researches on observations during Ulysses' first and second polar flybyes made by Phillips in 1995 and McComas in 2003 demonstrate that the solar wind momentum flux density scaled to 1 AU is almost invariant except that it is slightly small in the latitude of ±10°-30°, thus the solar wind speed can be derived from this conclusion and the obtained density data. The model is applied to study the solar wind background in Carrington Rotation (CR) 1918 and the results are roughly consistent with the observations in solar minimum. However, the area of high density and slow speed is slightly larger than that observed and thus the density model needs to be further improved.
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    Metric Type Ⅲ Radio Bursts and Coronal Mass Ejection
    MA Yuan;WANG Deyu;HUANG Guangli
    2006, 26 (3):  167-171.  doi: 10.11728/cjss2006.03.167
    Abstract ( 2138 )   PDF (1185KB) ( 989 )   Save
    Statistical analyses of the correlation events between the type Ⅲ radio bursts and Coronal Mass Ejections (CMEs) during 23rd cycle are presented, radio data were observed with the 20-420 MHz at the Radio Spectrograph Culgoora Solar Observatory in Australia. It is found that the relation between the decimetric type Ⅲ bursts and CMEs is not closer than the relation between the type Ⅱ radio bursts and CMEs. Most of metric type Ⅲ radio bursts occurred 25-30 min before CME, and about 72% CMEs events correlated with gradual flares. Meanwhile, the higher energy of theflare corresponds to the larger initial velocity of the correlated CMEs. As for impulsive flares, the type Ⅲ bursts are produced probably owing to the ejection of high energy electronic beam from the open magnetic line of force. And around the electronic beam and along the open magnetic line of force there simultaneously ejects a plasma block mass, which just form a small-scale CME. In this way, the type Ⅲ burst and CME occur in the same flare. As for gradual flare, a prominence is formed possibly owing to the uninterrupted upward floatation of the magnetic flux tube in the flare. The ejection matter of the prominence produces the large-scale CME, but on the edge of the magnetic flux loop there exists the open magnetic field line, the energetic electronic beam can eject and produce type Ⅲ bursts.
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    Statistical Characteristics of Ionospheric Absorption Spike Events at Zhongshan Station
    DENG Zhongxin;LIU Ruiyuan;ZHAO Zhengyu;YANG Huigen;XU Zhonghua
    2006, 26 (3):  172-176.  doi: 10.11728/cjss2006.03.172
    Abstract ( 1914 )   PDF (1780KB) ( 1133 )   Save
    The total number of 189 ionospheric absorption spike events was identified in the imaging riometer's data from 2000 to 2001 at Zhongshan station, Antarctica. All events are divided into two groups, the nightside events (69 samples) and the dayside events (120 samples) according to their occurring time. The whole features are found with regard to their occurrence, duration, intensity, shape, size, movement and the relationship with Kp by using statistical methods. The occurrence peak of the nightside spike event is around magnetic per-midnight and in April, while the occurrence peak of the dayside spike event is around magnetic noon and in August. It is suggested that the nightside spike events are closely related to the aurora substorm activities, while the dayside spike events are affected by the solar wind conditions. The typical duration of the spike events is 2 - 3 minutes. The maximum intensities of absorption are usually less than 1 dB. The shape of the spike is most like elliptic with the major axis along the geomagnetic east-west direction. Comparisons have been made on the occurrence of the spike events between Zhongshan station and arctic stations. The possible mechanisms which cause the spike events are suggested in the paper.
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    Comparison Between the TIMED Observed Global Temperature Distribution and the NRLMSISE-00 Empirical Atmospheric Model
    XU Jiyao;JI Qiao;YUAN Wei;MA Ruiping
    2006, 26 (3):  177-182.  doi: 10.11728/cjss2006.03.177
    Abstract ( 2087 )   PDF (5452KB) ( 1421 )   Save
    In this paper, the comparison between the TIMED observed global temperature distribution and the temperature calculated by the NRLMSISE-00 empirical atmospheric model is made. The comparison indicates that in the altitude region between 20-70km, the global temperature structure calculated by the NRLMSISE-00 empirical atmospheric model is consistent with the satellite observation. However, the comparison shows that in the mesopause region, there is obvious difference between the NRLMSISE-00 empirical atmospheric model and the satellite observation. In the vernal equinox season, there is a stable Mesospheric temperature Inversion Layer (MIL) in the lower latitude (20°S-20°N) mesopause region in the satellite observed global temperature data. But the NRLMSISE-00 empirical atmospheric model can't produce this feature. The satellite observation indicates that there are two distinctive levels worldwide of the mesopause altitude. One is at about 100 km, another is at about 85 km. This characteristic can't be exhibited by the NRLMSISE- 00 empirical atmospheric model. On the other hand, there is large difference of the temperature distribution between the empirical atmospheric model and the satellite observation in the lower thermosphere.
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    Forecasting Dst Index With Artificial Neural Network
    XUE Bingsen;GONG Jiancun
    2006, 26 (3):  183-186.  doi: 10.11728/cjss2006.03.183
    Abstract ( 2075 )   PDF (991KB) ( 1236 )   Save
    In this work, fully connected neural network, a new kind of artificial network, has been introduced to construct the model for Dst index forecasting, Through studying the mechanism that the geomagnetosphere was affected by the condition of interplanetary media, the geomagnetic disturbance index Dst was found to have close, and complex relationship with both the solar wind parameters and IMF features. By employing the measured parameters from ACE spacecraft, these parameters were the solar wind velocity, the density of solar wind plasma and the southward component of IMF. The most recent measured Dst was also figured to correlate to the Dst several hours ahead. To construct the relationship between interplanetary measured parameters and Dst index, fully connected neural network was introduced. This neural network could demonstrate the complex relationship through building up the internal connection between separate neurons in hidden layer. After a training process with historical data, the forecast model was built during which the neural network will adjust the internal connect weight between units automatically according to the input parameters. The storm time data of 1998 and 1999 was selected in the training process of model construction. The data set during the geomagnetic storm in July 24-29 was used to test the model and the error of the test data was 14.3%.
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    Optimization and Design of Baseline Direction of Satellite InSAR System
    WU Weiqi;Zhang Yulin
    2006, 26 (3):  187-192.  doi: 10.11728/cjss2006.03.187
    Abstract ( 1724 )   PDF (3562KB) ( 985 )   Save
    The satellites SAR system is an imaging technology that has been paid much attention recently, one of the examples is InSAR system, which provide 3D image by interferential height measurement based on the formation flying satellites' baselines. In formation flight InSAR system, the configuration of satellites' constellation should be carefully designed to achieve a high precision and good quality. In this paper, the influence of height measurement accuracy that caused by satellites relative motion is studied with analysis on measurement precision of the height and flight dynamics. Two types of baseline directions were discussed in particular. One type is "vertical baseline" and the other is "horizontal baseline". On the basis of analysis, the concept of "preponderant arc" is put forward. The analysis can be used to determine the satellites' formation. Utilizing Hill~equation, the expressions of how the length, azimuth angle and pitch angle transformed with time were given. Finally, a new constellation configuration different from current system based on the analysis results is proposed. This formation includes three satellites, two satellites run concomitantly in a vertical plane, and the other runs in a sidelong plane. Some basic analyses for the performance are also presented. The simulation shows that this formation is feasible.
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    Geostationary Satellite's End-of-Life Predication Based on Propellant-Remaining Estimation
    LI Jiancheng;YANG Yongan;AN Jinwen
    2006, 26 (3):  193-196.  doi: 10.11728/cjss2006.03.193
    Abstract ( 2184 )   PDF (3562KB) ( 1263 )   Save
    With the application of the geostationary satellites, the problem how to prediction the in-orbit life of the satellites is taken into account, especially the satellites with liquid propellant. The methods of propellant measurement and management have been studied by many people, and the assignment and the end-of-life prediction is thought to be a necessary work in satellite engineering. This paper discusses the factors that may influence the in-orbit life of geostationary satellite, such as space environment, capability of the equipment, the wasting fuel and the ground operation. The propellant mass is proved to be the main factor in engineering. The end-of-life prediction accuracy analysis should be based on the on-board sensor accuracies and satellite telemetry processing accuracies. The methods of how to measure and estimate the propellant-remaining of the Chinese satellite are given as PVT method, BookKeeping (BK) method, and combined method (PVT+BK). The prediction methods of the satellite give the average life, the reliable life and the actual life. The engineering example shows the predication method based on propellant-remaining is reasonable.
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    Double-Satellite Formation Constellation States Determination With GPS and
    HU Limin;WANG Wei;XI Xiaoning
    2006, 26 (3):  197-202.  doi: 10.11728/cjss2006.03.197
    Abstract ( 2372 )   PDF (758KB) ( 1158 )   Save
    The states determination of formation constellation is an important research task. CPS is a chief means, which uses two observational signals: pseudo-range with an accuracy of 10 m, and carrier phase with an accuracy of 10^-3 m. Benefiting from AFF (Autonomous Formation Flying) technology, an assistant means "CPS-like" ranging technology is introduced to improve the states results, which can provide more accurate relative measurement information that are owed to shorter pseudo-code length and wavelength of carrier phase comparing to that of CPS technology. The states determination problem with double-satellite formation constellation for the earth-observation purpose is dicussed. The mathematical model combines "CPS-like" ranging technology with CPS is developed. Single GPS inter-satellite integer ambiguity and single "GPS-like" intra-satellite integer ambiguity are quickly and simultaneously initialized. Finally, these models above mentioned are simulated. The results of our tests indicate the formation states are improved significantly, with the accuracy of relative position reaching 10^-3 m and the accuracies of absolute attitudes reaching 10^-4 rad. The method proves to be valid through simulation.
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    Study and Comparison of Several Passive Positioning Algorithms About
    YANG Long;XU Dongmei;ZHANG Shouxin;DONG Xurong
    2006, 26 (3):  203-208.  doi: 10.11728/cjss2006.03.203
    Abstract ( 2225 )   PDF (1804KB) ( 1267 )   Save
    There are only 2 or 3 satellites in the "Beidou" satellite navigation system, so it alone can not meet the demand of passive positioning algorithm. Three kinds of passive positioning algorithms about "Beidou" satellite navigation system are presented and compared: 2 satellites algorithm, 3 satellites 3 unknowns algorithm and 3 satellites 4 unknowns algorithm. The measurable parameters have been increased by adding height measurement and the unknowns have been decreased by modeling the receiver clock error with a 2 order polynomial. The availability of backup satellite of the "Beidou" navigation system is also studied. In addition, a technique named "quasi-differrential" correction scheme has been proposed. The positioning accuracy is improved by this technique. The experiment results show that all the three algorithms can achieve the accuracy of 100 m which can meet the common user's positioning demand.
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    Algorithm for CCD Star Image Rapid Locating
    WANG Zhaokui;ZHANG Yulin
    2006, 26 (3):  209-214.  doi: 10.11728/cjss2006.03.209
    Abstract ( 2187 )   PDF (1336KB) ( 1506 )   Save
    Rapid processing of large scale CCD star image is a key technique for new type of star sensor as well as space surveillance sensor. The foreground of CCD star image is differ form the background distinctly. Majority pixels of the image belong of the background. The typical histogram of CCD star image has a two-peak values structure. Base on those analyses, a strategy for star image's pretreatment was presented. The background and noise of the image is removed by a window transform of the pixel gray, all pixel whose gray value below the threshold will be set as a black pixel, the gray of which will be set as zero videlicet. The threshold is determined through the numeric statement of the background pixels by an iterative algorithm. Then a new algorithm for star point locating was presented by a two-step projection checking method. The horizon domains of the star points can be determined through the vertical projection checking of the image at first, then the horizon domain of each star point can be determined through the horizon projection in the horizon domains of the star points. The precise position of the star points is calculated using centroid method at last. The new algorithm is simpler and has smaller consumption of computing and memory than tradition connected domain methods. Experiments on real star images with size of 2048 × 2048 indicated the validity of the algorithm.
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    Analysis of Possibility of Disturbance From Celestial Bodies on Satellite-Carried Optical Sensors
    LIU Yanzhu
    2006, 26 (3):  215-219.  doi: 10.11728/cjss2006.03.215
    Abstract ( 1856 )   PDF (1622KB) ( 1239 )   Save
    The satellite-carried optical sensors with various objectives may be possibly disturbed by the entrance of celestial bodies, such as sun, moon and earth into the sensitive area of sensors. In this paper, two kinds of satellite-carried optical sensors are discussed. They are the star sensor with a sensitive axe fixed on the spacecraft, and the satellite-carried astronomical telescope with a sensitive axe fixed in the space. A sensitive sector area of the optical sensor in the ecliptic plane or in the moon's plane is defined as the projective of the sensitive cone of the sensor on these planes. The disturbance occurs when the satellite-sun or satellite-moon vector enters into the sensitive sector area of the star sensor. A disturbance cone of the earth is formed from the satellite-earth vector and the contour of the earch. The disturbance occurs when the disturbance cone intersects the sensitive cone of the telescope. Based on the geometric relationships the conditions of disturbance from celestial bodies on the satellite-carried optical sensors can be determined and some formulas are derived to determine the time of occurrence of disturbance
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    Deployment Dynamic Analysis of Circular Truss Deployable Antenna With Friction
    ZHAO Mengliang;GUAN Puling
    2006, 26 (3):  220-226.  doi: 10.11728/cjss2006.03.220
    Abstract ( 1931 )   PDF (2147KB) ( 1385 )   Save
    Through a design of circular truss deployable antenna model, the primary layout and deployable mechanism and the primary technique requirements are introduced in detail. In order to provide reference for optimization design and predict the dynamic performance of the deployable structure in orbit accurately, deployment dynamic analysis of the structure with friction is essential. The movement property of deployable space truss structure is analyzed with the Moore-Penrose generalized inverse method. A practical mathematic algorithm is presented to formulate the constraint equations and the relevant Jacobian matrices, and to simulate the constraint conditions of the structural deployment effectively. By studying the non-linear action mechanism of the friction during deployment, the dynamic equations of Coulomb friction and viscous friction for the deployable structures are established. Based on the above work, deployment dynamic analysis of circular truss deployable antenna with friction is carried out. The deployment dynamic of a circular truss deployable structure is simulated with friction effects and without friction. The numerical simulations show that the analytical process is efficient for deployment dynamic analysis of circular truss deployable antenna with friction.
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    Three-Dimensional Dynamic Modeling and Simulation of a Beam Attached to a Spatially Moving Base
    XIAO Jianqiang;ZHANG Dingguo
    2006, 26 (3):  227-234.  doi: 10.11728/cjss2006.03.227
    Abstract ( 1841 )   PDF (1666KB) ( 1203 )   Save
    The three-dimensional dynamics of a flexible cantilever beam attached to a moving rigid body undergoing an arbitrarily three-dimensional large overall motion is investigated in this paper. A set of dynamic equations for two-dimensional transverse and one-dimensional longitudinal vibrations of the flexible beam is established by using Lagrange's governing equations of motions the coupling effects of dynamic method. In the construction of the the so called transverse deformation-induced longitudinal deformation is included, which leads to the consideration of the dynamic stiffening effects in the obtained dynamic equations. An example is given to show the validity of the method presented in this paper and also the significant effects of the dynamic stiffening terms on the deformation and the dynamic characteristic of the flexible beam, and the difference between the present modeling theory and the traditional vibration theory as well. The traditional vibration theory of flexible beam will produce large error when the flexible beam itself is at higher speed large overall motion. Once the speed reaches at a critical value, the traditional dynamic system will diverge. Whereas the present model has high precision and the dynamic system converges even if the flexible beam undergoes higher speed large overall motion.
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    Functional Simulations of the Fire Precursor of the Wire Insulation in Quiescent Microgravity Enviroment
    CHEN Lifen;XIN Zhe;KONG Wenjun;LAO Shiqi;ZHANG Xiaoqian
    2006, 26 (3):  235-240.  doi: 10.11728/cjss2006.03.235
    Abstract ( 1751 )   PDF (1793KB) ( 964 )   Save
    The experimental principle of Functional Simulation (FS) was proposed aiming at the fire in the space shuttle caused by the electrical wire overload or short circuit because it is of great important significance of study on the wire insulation flammability in microgravity for fire safety. The concept and conditions of the FS were presented in this paper, Experimental setup was established according to the FS concept. The study on the fire precursor of the wire in microgravity was accomplished by the proposed experiment facility at normal gravity. The experimental results show that the equilibrium temperatures of wire insulation were much higher in the microgravity than that in the normal gravity condition with the overload currents because the convection is greatly reduced and suppressed, Meanwhile, the wire was molten down and the insulation was burnt observed in the experiments. These results furtherly confirmed that the wire is the potential ignition source in the case of overloading or short circuit in the space shuttles.
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