2007 Vol. 27, No. 4

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Analysis of Solar Activities and Changes
HAO Lisheng, BI Baogui, YAO Xuexiang
2007, 27(4): 265-270. doi: 10.11728/cjss2007.04.265
Abstract(2501) PDF 2251KB(1208)
Abstract:
Solar activities have obvious effects on earth＇s climate. Many scientists have studied the relationship between solar activities and climate change, and a lot of papers have been published in this field. The relative sunspot numbers is an important factor in the research of solar activities. Wavelet transform is a fine method to analyze time serials periods. By using different data, the periods are different. In the past time, many scholars had analyzed solar activities by others statistical methods, found that changes of solar activity have periods of 5-6 years, 11 years, 22 years, 80-100 years, and so on. The periods are so disunity that they can＇t be better used to forecast change trend of solar activities. In this paper, being applied to analysis of solar activities, the wavelet transform method was introduced to analyze periods change, and found some meaningful results. The relative sunspot numbers change with periods of 10.7 year and 101 year. The 10.7 year period is remarkable, and it＇s amplitude varies with time. In 1935 to 2000, the amplitude of 10.7 year period are especially distinct. The solar activities exist strong or weak phases. Abrupt change occurred in 1950 year, and solar activities became stronger since 1950. It is predicled that the solar activity will be weaker in the near future.
Role of Expansion Velocity of Magnetic Clouds in Flux Rope Model
XIA Qian, SHEN Chenglong, WANG Yuming, YE Pinzhong
2007, 27(4): 271-278. doi: 10.11728/cjss2007.04.271
Abstract(2661) PDF 2954KB(1130)
Abstract:
In order to examine the influence of magnetic cloud＇s expansion on its cylindrical flux rope model. The parameter of MC of 15 typical magnetic clouds with Dstmin 〈 -50 nT during 1998-2003 are fitted by applying static and expanding flux rope models, the Multi-MC events and the shock propagation in MC events are not take into account. It is found that the RMS deviations of the fitting results by the expanding model are all less than or equal to those by the static model, it reduced the error up to 30%. That the peak of the magnetic filed in MC is at the leading end in expanding models, this more consistence with the observations than static model. The inferred expansion speeds of these magnetic clouds are consistent with previous statistical results that the expanding speed of MC is at the order of backgoud Alfvén speed. Thus the expanding model matches much more to observed magnetic clouds than the static model. Some differences of the fitted magneticclouds＇ parameters between the two models are analyzed.
Central and Northern China TEC Map Using the Kriging Method
MAO Tian, WAN Weixing, SUN Lingfeng
2007, 27(4): 279-285. doi: 10.11728/cjss2007.04.279
Abstract(2936) PDF 2246KB(1788)
Abstract:
In this paper the Kriging method was introduced to map Central and Northern China （30°N-55°N, 70°E-140°E） Total Electron Content （TEC） Map （CNC TEC Map）. Firstly, three popular ionosphere models （Klobuchar model, IRI and JPL GIM） were compared with grid TEC. Then CNC TEC Map using Kriging method with constant drift, linear drift and quadratic drift were compared with each other. Then TEC map derived from nearest neighbor method, polynomial regression method （order=5） and Kriging method with different temporal resolution of 5 minutes, 30 minutes and 120 minutes were compared. The result revealed that even in the mid-latitude area, these popular ionosphere models showed great differences from observation; that the results of the Kriging algorithms were similar which led us go use ordinary Kriging method, i.e. Kriging method with constant drift; and that the Kriging method was begger than other methods, especially when temporal resolution was high.
Study on a Method of Calculating the Ionosphere TEC Using RDSS System Observation Data
XU Lijuan, YUAN Hong, FAN Jianjun, LIAO Bingyu
2007, 27(4): 286-291. doi: 10.11728/cjss2007.04.286
Abstract(2255) PDF 1944KB(1082)
Abstract:
In this paper, a method of calculating the ionosphere TEC （Total Electron Content） is proposed using RDSS （Radio Determination Satellite Service） System observation data, and gained the ionosphere vertical TEC and its diurnal variation tendency of center station region using one month＇s data. The result indicates that the ionosphere TEC derived from the RDSS observational data touch bottom at about 4 o＇clock and come to a peak at 14 o＇clock （Beijing Time）, which matches the physical rule that the ionosphere is affected by the solar zenith angle. Using the calculating method introduced in this paper, the TEC of ionosphere can be properly derived, and the trend of TEC would be properly got. This method is feasible and valid. Some errors, which might exist, are also disassed in this paper.
Effect of the Relaxation Characteristic Length of Modulated Electron Beam on Whistler Wave Radiation
WANG Yan, YANG Yong, ZHAO Zhengyu
2007, 27(4): 292-297. doi: 10.11728/cjss2007.04.292
Abstract(2308) PDF 1016KB(981)
Abstract:
During the active space experiments of radiating the modulated electron beam, the linear and nonlinear interaction between the electron beam and background plasma may excite whistler wave. Characteristics of the excitation are determined by many factors, including velocity, relaxation characters of electron beam, the frequency of excited waves, and the density of background plasma. The relaxation characteristic length of the modulated electron beam is one of the important factors. In this paper, the influence caused by the exponential attenuation relaxation characteristic length of the modulated electron beam upon the characteristics of the wave excited by the electron beam were studied. Through solving the wave equation when the electron beam is injected into the homogeneous anisotropy space plasma, the solution of the dispersion equation and the Poynting vector representation of the excited wave are obtained. It was shown that the wave radiation intensity excited by the modulated electron beam is enhanced efficiently when the relaxation characteristic length of the electron beam is comparable with the characteristic size of inhomogeneous background plasma.
Response of Medium Energy Electrons Fluxes to Geomagnetic Disturbance at Low Orbit
YANG Xiaochao, WANG Shijin
2007, 27(4): 298-302. doi: 10.11728/cjss2007.04.298
Abstract(2258) PDF 1788KB(1057)
Abstract:
According to the observational result of space electron environment, the medium energy electron fluxes of space radiation environment are modulated by geomagnetic activity at low earth orbit. In this paper we utilize the data of ZY-2 satellite Space Environment Monitor （SEM） system from 2004 to now, the data of American NOAA satellite （NOAA-15, NOAA-16, NOAA-17） SEM system Medium Energy Proton and Electron Detector （MEPED） from 1998 to now, and the observational result of geomagnetic activity to analyze the response characteristics of medium energy electrons fluxes to geomagnetic activity in the range of high-latitude at low earth orbit （about 500-900 km）. The results present that the fluxes of medium energy electrons are closely correlated with geomagnetic storms and substorms, the geomagnetic disturbance stronger, the enhancing of medium energy electron flux higher. While strong geomagnetic storms happen, the fluxes of medium energy electrons usually enhance 1 order of magnitude. And the absolute enhancements of daily averaged electron fluxes are correlated with the energy of electrons, the energy of electrons higher, the absolute enhancement of daily averaged electron flux larger. Usually, there is several days delay between the peak of geomagnetic disturbance and the peak of medium energy electrons fluxes.
Spin Satellite Attitude Determined by Aboard Magnetometer
CHEN Tao, ZHANG Xiaoxin, LI Wenzeng, WANG Naiquan
2007, 27(4): 303-308. doi: 10.11728/cjss2007.04.303
Abstract(2427) PDF 2713KB(1084)
Abstract:
The method and procedure that can determine the parameters of satellite spin axis by the scientific data of magnetometer on board near perigee are presented in this paper. Their importance to scientific exploration and satellite running are expressed too. It is emphasized that two fundamental condition of using this method are that the satellite＇ spin need to be basically stable and the satellite＇s perigee should be not so much high （below 1000 km）. The key operation of the special work is： （1） Determination of model geomagnetic field values by orbit parameters near perigee, （2） Determination of the angle values of satellite spin axis orientation by comparison of the data from magnetometer on satellite near perigee with model geomagnetic field values. The accuracy and application effectiveness on TC-1 satellites and TC-2 satellite of this method are illustrated and compared. It can be concluded that this method and operation demonstrated in this paper is very effective in satellite experiments. They have shown greatly significance in scientific analysis and future satellite application.
Simulation and Validation for CRRES Satellite Internal Charging Effects
LI Xuesheng, JIAO Weixin
2007, 27(4): 309-314. doi: 10.11728/cjss2007.04.309
Abstract(2216) PDF 1719KB(1217)
Abstract:
Firstly, a method based on the Geant 4 software is introduced. It can calculate the electric field arisen from internal charging effects under the special space environment. Secondly, the space electron environment CRRES satellite was located on was analyzed and used to simulate the internal charging effects. Lastly, the attempt has been made to compare the data from the CRRES IDM space experiment and the data from simulation results. This comparation showed that the calculation method is validated and some basic conclusions about the space environment which causes the internal charging effects are drawn. The calculations show that the high-energy electron flux/energy spectra is the primary cause of discharges. The material characteristics, especially the RIC （Radiation Induced Conductivity） and dose rate factor kp are very important to the steady state electric field. For studying the internal charging effects, need to mensurate these material characteristics accurately in laboratory.
Measurements and Analysis of Plasma Column Discharge Impedance
XU Jie, ZHAO Guowei, LIANG Zhiwei, WANG Zhijiang, XU Yuemin
2007, 27(4): 315-320. doi: 10.11728/cjss2007.04.315
Abstract(2110) PDF 1962KB(1308)
Abstract:
Recently a large number of surface-wave plasmas experimental data have been accumulated, so their modeling is well advanced and they have found applications in various fields of research and technology. An experiment to measure surface-wave plasma column discharge impedance has been designed, using the principle of impedance matching in transmission line. Refer to the method to work out the radiation impedance and loss impedance of metal antenna, plasma column discharge impedance is calculated in the simplest cases and compared with experimental results. It is shown that surface-wave plasma column discharge impedance plays an important part in analyzing the efficiency of plasma source and diagnosing plasma parameters such as densities, temperatures. This study will be of great importance for further scientific and engineering work in order to meet the demands of the various diverse plasma technological applications.
A Method for Estimating Space Debris Population and Distribution Based on Phased Array Radar Fence
SONG Zhengxin, TANG Hui, HU Weidong, YU Wenxian
2007, 27(4): 321-326. doi: 10.11728/cjss2007.04.321
Abstract(3037) PDF 2354KB(1009)
Abstract:
With more and more space activities such as manned space operations and space station missions, concern with hazards of small-size space debris, especially those of 1-10 cm, is increasing. Limited by sensor sensitivity and data processing capability, they cannot be routinely tracked or cataloged. Therefore, statistical characterization technique is relied on to acquire knowledge on small-size space debris, i.e. to estimate population and distribution of them. Based on a simplified phased array radar fence for space debris detection, a method for estimating space debris population and distribution in altitude and inclination using statistical technique is proposed. The method uses only orbit altitude and inclination data measured and the time of debris crossing the radar fence, and does not depend on a priori information of space debris environment. Because of the relatively sparse distribution of space debris, the problem whether one debris object that may be detected by the radar fence （i.e. inclination and radar cross section are large enough） actually crosses it can be modeled as a Poisson process. For debris objects in a given altitude or inclination bin, the average rate of crossing the radar fence is derived. A companied company with the average crossing rate measured, space debris population in the given altitude bin or inclination bin is obtained. Then the total number of debris objects and their When radar cross section data can be secured, distribution in altitude and inclination are acquired. the method can also be used to estimate space debris population distribution in size. The simulation results show the validity of the proposed method.
On Orbit Lifetime of HEO Objects
LIU Lin, TANG Jingshi
2007, 27(4): 327-335. doi: 10.11728/cjss2007.04.327
Abstract(2717) PDF 3132KB(1264)
Abstract:
The lifetime of the low orbit earth satellite is mainly dominated by atmospheric drag. The satellite loses altitude in the dense atmosphere and eventually falls. However, the lifetime of space objects of HEO type, which goes in a large-eccentricity ellipse with very low perigee altitude and very high apogee altitude, is determined mainly by third-body （Sun and Moon） perturbation, as well as its initial state, which, closely related to RAAN Ω and Argument of Perigee ω, determines the long periodic evolution of the eccentricity. Here examples are taken for Geosynchronous Transfer Orbit debris and the orbit lifetime are estimated for double stars TC-land TC-2, proving that two GTO debris with the same initial elements but 3 hour＇s difference in entering expected orbits will have distinct destinies, the same conclusion is also valid for TC-1 and TC-2. All the mentioned distinction could be resulted in by third-body perturbation and a difference in initial elements （Ω and ω）. This paper would end up with a detailed computation, which accords with previous analysis.
Attitude Control of Large Angle Maneuver for Microsatellite Using Variable Speed Control Moment Gyros
LIU Jun, HAN Chao
2007, 27(4): 336-341. doi: 10.11728/cjss2007.04.336
Abstract(2562) PDF 1406KB(1299)
Abstract:
The multi-projects rapid attitude maneuver problem for agile microsatellites with VSCMG （Variable Speed Control Moment Gyros） as actuators was investigated. VSCMG is a recently introduced actuator for spacecraft attitude control, and it is a hybrid one between two types of internal torque generators; namely, a conventional control moment gyro and a reaction wheel. These actuators can provide unique torque, angular momentum and slew rate capabilities to microsatellites without any increase in power, mass or volume. This will help microsatellites become more agile. The attitude dynamic equation of a spacecraft with VSCMG attached was presented, the attitude was described by MRP （Modified Rodrigues Parameters）. A nonlinear feedback controller based on Lyapunov stability condition was developed under various physical constraints, including the actuator saturation, slew rate limit, control bandwidth limit, etc. A numerical simulation was presented on the sample of the attitude maneuver of a microsatellite with VSCMG. Simulation results demonstrate the effectiveness and robust performance of the proposed nonlinear feedback control system.
Study on Inter-Satellite High Accuracy Ranging Technology for Gravity Satellite
SHEN Jian, SHE Shigang, Wang Kai, HE Dan, HUANG Yichang
2007, 27(4): 342-346. doi: 10.11728/cjss2007.04.342
Abstract(2448) PDF 1887KB(1310)
Abstract:
Satellite-to-satellite tracking is one of the most promising and valuable methods for gravity field determination. The high accuracy inter-satellite ranging system is the major payload of gravity exploring satellite using satellite to satellite tracking in low-low model. K Band Ranging system （KBR） on the Gravity Recovery and Climate Experiment （GRACE） satellite is a micron-level ranging system. The geopotential is determined by processing precise range or range rate observed between the two satellites. GRACE has ushered in a new era for satellite measurement of the Earth system. The tremendous advances made by GRACE have led to an interest in launching a follow-on mission with even more ambitious scientific goals. A higher accuracy laser interferometric ranging system is proposed for GRACE follow-on mission. A strawman flight design, an error budget, and a demonstration laboratory breadboard are developed in foreign country. Based on the study of KBR and laser ranging system＇s measurement principle, the fundamental structure of KBR was presented in this paper. The key technology of these two ranging system and the current research level of our country are analyzed in detail. At the same time, some suggestions are proposed for the future inter-satellite ranging project of China.
Adaptive Control for Free-Floating Dual-Arm Space Robot System in Joint Space
HONG Zhaobin, CHEN Li
2007, 27(4): 347-352. doi: 10.11728/cjss2007.04.347
Abstract(2697) PDF 1283KB(1299)
Abstract:
In this paper, the dynamics and control problems of free-floating dual-arm space robot system is studied. With the momentum conservation of system, the kinematics and dynamics of system are analyzed. It is verified that the dynamic equations of the system can be linearly dependent on a group of inertial parameters. Based on the results and with the augmentation approach, an adaptive control scheme for space robot system with unknown payload parameters to track the desired trajectory in joint space is developed. The control scheme proposed above is structurally and computationally simple, because of an effective exploitation of the system dynamics. In particular, it doesn＇t require measuring the position, velocity nor acceleration of the base. And the numerical simulation is carried out, which confirms the controller proposed is feasible and effective.

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