2006 Vol. 26, No. 5

Display Method:
Study of the Response of the Ionosphere Over Sun-Lit Boundary Region to Solar Flare
ZHANG Donghe, LI Qiang, QIN Jiansheng, XIE Shibiao, ZHAO Yingxine YE Jinfenge MO Xiaohua, XIAO Zuo
2006, 26(5): 321-325. doi: 10.11728/cjss2006.05.321
Abstract(2610) PDF 1438KB(1221)
Using the model of solar irradiance spectrum during large solar flare and MSIS, the electron production rate during flare over sun-lit boundary region is calculated. It is found that during large solar flare the obvious increase of electron production rate over sun-lit boundary region occurs that, in turn cause the sudden increase of total electron content observed in this region. From the profile of electron production rate in different solar zenith angle, it can be seen that the largest electron production rate decreases with the zenith angle increasing and the heights of peak electron production rate increase. Calculation shows that the double peaks exist in the profile of electron production rate when the zenith angle less than 90° that correspond to ionospheric E and F region. Nevertheless, the peak value of electron production rate in F region is more larger than that in E region when zenith angle larger than 90°. Considering the feature of recombination of electron and ion in different ionospheric regions, it can be concluded that the sudden increase of total electron content observed by GPS mainly occurs in F region over sun-lit boundary region.
A Statistical Study on Signal to Noise Ratio of GPS Beacon
XIONG Bo, WAN Weixing
2006, 26(5): 326-330. doi: 10.11728/cjss2006.05.326
Abstract(3235) PDF 3033KB(1292)
The Signal to Noise Ratio (SNR) of GPS satellites beacon is mainly influenced by the gain of GPS satellites transmitter and receives on the ground, the geometrical distance between GPS satellites and receives, the elevation of the receives and the ionosphere medium attenuation. In this paper, a method is proposed to separate ionospheric attenuation from the observation of SNR. The technique was used to analyze the data observed at MANA station (273.751°E, 12.149°N) in 2003, and to construct a mean diurnal change pattern of the ionosphere medium attenuation. Comparing with the attenuation value calculated using IRI. It shows that the result fits with IRI well in the change of the attenuation value of SNR with the local time, when GPS signal radio vertically penetrates through the ionosphere.
Response of Mesosphere and Lower Thermosphere to a Localized and Time-Variable Thermal Source
XIE Bian, ZHANG Shaodong
2006, 26(5): 331-337. doi: 10.11728/cjss2006.05.331
Abstract(1950) PDF 2294KB(1398)
By using the alternative-direction-implicit scheme, a two-dimensional fully nonlinear compressible atmospheric dynamic model is established, with which, the responses of the mesosphere and lower thermosphere to a localized and time-variable thermal source and a momentum forcing source in the troposphere are numerically simulated respectively. And then the energy density, the horizontal and vertical wavenumber and the frequency of the response are analyzed. The numerical results show that the response carrying the energy propagates from the troposphere and lower stratosphere upward to the mesosphere and lower thermosphere within a relatively narrow horizontal field which is symmetrical about the horizontal location of the heat source. The effect of the heat source upon the response is much stronger than that of the momentum forcing source. It is different in affecting the frequency, the horizontal wave length and the vertical wave length of the induced gravity wave. The horizontal wave length can be determined by the horizontal scale of the heat source, the frequency of the response is almost the same with the heat source with high frequency in the simulation, but the vertical wave length of the response is much larger than the vertical scale of the source. Usually, the longer the horizontal scale of the thermal source is, the larger the vertical wave length of the induced gravity wave.
The Saturation and Breakdown of the Nonlinear Propagation of Gravity Wave
LIU Xiao, XU JiyaoI MA Ruiping
2006, 26(5): 337-345. doi: 10.11728/cjss2006.05.337
Abstract(2232) PDF 2676KB(1247)
A time splitting numerical model is developed in this paper, which combined the explicit algorithm in the horizontal direction and the implicit algorithm in the vertical direction, and used to simulate the nonlinear propagation of the gravity wave (GW) in a 2-dimensional compressible atmo- sphere. Numerical simulation of the nonlinear propagation of the small amplitude GW is presented by using this model. The numerical results coincide well with linear theory and indicate that the numerical model is correct. The saturation and breakdown of the nonlinear propagation of the finite amplitude GW is simulated by using the model. The results show that: (1) The overturn appears before the saturation of GW, however, it requires a long time (nearly 1.5 periods of the GW) to induce the GW breakdown. The height (time) of instability predicted by linear saturation theory is higher (latter) than the corresponding results obtained from nonlinear numerical simulation because of the nonlinear wave-wave and wave-flow interaction. (2) The nonlinear wave-flow interaction produces energy transforring from the GW to mean flow prior to instability. The nonlinear wave-wave interaction is induced by the breakdown of GW directly. (3) The direction of the horizontal mean wind acceleration, the jet and the horizontal propagation of GW are consistent and indicate that the nonlinear wave-flow interaction accelerate the formation of horizontal mean wind shear and the development of the instability.
Observational Evidences and Simulation of Tide Wind Induced Mid-Latitude Sporadic E-Layers
ZUO Xiaomin, WAN Weixing, TAN Hui
2006, 26(5): 346-351. doi: 10.11728/cjss2006.05.346
Abstract(2338) PDF 1857KB(1070)
The present paper deals with both the statistical study and the computer simulation of sporadic E-layers at mid-latitude regions. The Fourier transformation of the foes sequence shows that the observational data have a strong 24 h and 12 h periodic component, which means strong correlation of Es with the atmospheric tides. The sporadic E occurrence has one peak at higher latitudes while has double peaks at lower latitudes, which suggests that the sporadic E occurrence is associated with the diurnal and semi-diurnal tides. The simulation work is based on the continuity equation and momentum equation. Method of characteristic curve is adopted. According to the widely studied wind shear theory, simulation for the convergence of metal ions to form a thin layer induced by the tidal wind has been carried out. In conclusion, the strong correlation between the sporadic E-layers and the tide is confirmed not only from the statistical analysis of observational data but also from the computer numerical simulation work.
An Improvement on Retrieval Method of Total Ozone's Determination Using Backscattered Ultraviolet Earth Radiances' Measurements
JIANG Fang, WANG Yingjian, WANG Yongmei
2006, 26(5): 352-356. doi: 10.11728/cjss2006.05.352
Abstract(2021) PDF 1280KB(1026)
Values of the total ozone content of an atmospheric column are estimated from the simulated measurements of the intensity of radiation backscattered by a horizontally homogeneous earth-atmosphere system by means of SBDART radiative transfer computation mode with atmo- sphere containing varions kinds of aerosols. The retrieval method used is the Version7 algorithm. When all kinds of aerosols are present in the atmosphere the retrieval error is analyzed and the main reason which brings the error is the assumption of the residues being linear at the properly chosen triplet of wavelengths. In the paper a method is introduced to correct the initial ozone estimate Ω0 using the intensity radiation backscattered measured at different continuous ultraviolet spectral region which is selected on the basis of the ozone slant column density sΩ0. At last the results obtained by the new method and Version7 algorithm are compared. The comparing result proves the new method's validity.
Comparison of Mesospheric Fe and Na Layers'Variation Characteristic Times
WAN Shuang, YI Fan
2006, 26(5): 357-363. doi: 10.11728/cjss2006.05.357
Abstract(1888) PDF 2025KB(1059)
The chemical lifetime of the mesospheric ferrum and sodium layers is calculated using the EigenAnalysis (EA) method. For comparison, their meteoric smoke adsorption lifetime and vertical transportation lifetime are also computed. The results show that (1) at the altitudes around the peak number density of Fe layer, the EA chemical lifetime for Fe atom is several days, much longer than the traditionally defined chemical lifetime for Fe of several minutes, (2) below 84km chemical process prevails whereas above that height, vertical process dominates, and (3) among the four of meteoric injection process, chemical process, vertical transportation process, and meteoric smoke adsorption process, the most possible one that can make the cutoff heights of Fe and Na layers to be identical is meteoric smoke adsorption.
Analysis for Mars Laser Communications System in USA
MA Jing, XU Kehua, TAN Liying, WANG Jian
2006, 26(5): 364-379. doi: 10.11728/cjss2006.05.364
Abstract(2115) PDF 1252KB(1062)
Free Space optical communication havs many advantages, such as the small volume, the little mass, and the high data volume. Many countries nowadays focus on the development of free space optical communication techniques. Inter-satellite optical communication experimental success has built the confidence to deep optical communication techniques. The deep space optical communication technology started to develop later in China. So, refering to the system oversea is requested, such as the design of system, the selection of components and the parameters of system. This paper analyzed the MLCD are analyzed of USA in general, focused on the analysis of operational concept and principle for PAT subsystem, communication subsystem and ground terminal. The new components and new techniques used in MLCD are analyzed in details. Based on these analyses, the feasibility and reliability are also discussed.
Calibration Results of Solar X-ray Detector Aboard on FY-2C
KONG Linggao, WANG Shijing, LIN Huaan, WEI Fei
2006, 26(5): 370-376. doi: 10.11728/cjss2006.05.370
Abstract(2199) PDF 3345KB(1482)
The calibrating results of solar X-ray detector aboard on FY-2C are presented in this paper. The transducer of solar X-ray detector is proportional counter. The gas in the transducer is Ar. The solar X-ray detector can monitor the sun's X-ray flux above 4 keV in ten channels. The methods and results of experiments for calibrating are presented in detail. The radiation source used in these experiments are 241Am and 55Fe. The calibrating results are listed in six aspects: characteristics of plateau, efficiency, proportional characteristics, determining of energetic channels, energy resolution and time resolution. The plateau length is about 300 V. The plateau slope is less than 5%/100 V. The working voltage range of the detector is 1600-1900 V. The efficiency curve is calculated theoretically, and the material of the detector is taken into account. The experiments results show that the detector has good proportional characteristic. The time resolution of solar X-ray detector is 8.2 s. The solar X-ray detector aboard on GOES adopted ionization chamber, that is different from FY-2C. The detected results of solar X-ray detector aboard on FY-2C are compared with those of GOES. They fit well. The results show that the solar X-ray detector aboard on FY-2C works well to monitor the X-ray flux of the Sun and contribute much to the space environment monitoring.
Term Analysis of a TDRS Tracking a User Satellite
LI Yuheng, YI Kechu, TIAN Hongxin
2006, 26(5): 377-381. doi: 10.11728/cjss2006.05.377
Abstract(2266) PDF 1089KB(1114)
The space-based TT&:C network is a trend to be developed. The coverage of a TDRS tracking a user satellite is the first consideration for designers and depends on different elements. From the view point of engineering application, the terms of a TDRS tracking a user satellite are analyzed here in detail. Based on their orbital characteristics, the algorithm of a TDRS tracking user satellites without the earth blocking, which will diminish the coverage, is presented. Then the terms to decide whether the earth blocking happens are divided into three cases to be discussed in detail. The ways to accurately predicate the occurrence of earth block and sun interference are given here too. Despite of the two satellites being in line of sight, the position of the antenna fixed onboard a user satellite will cause exclusion sometimes. But, with the appropriate mast's length, it is sure for a TDRS to track the use satellite without any block when they are in line of sight. Therefore, the presented formulas and conclusions, which are verified by simulation means, are suitable for all cases. They can be used as means to determinate the number of TDRS to construct a space TT&C network and strategies to allocate the resource of an on-orbit TDRS to user satellites. It can improve the TT&C coverage for a TDRS tracking user satellites.
Comparisons of Two Kinds of GPS Broadcast Ephemeris Parameter Algorithms
CUI Xianqiang, JIAO Wenhai, JIA Xiaolin, HE Tao Xian
2006, 26(5): 382-387. doi: 10.11728/cjss2006.05.382
Abstract(2252) PDF 1556KB(1494)
The precision, efficiency and reliability of GPS broadcast ephemeris parameter algorithms are remarkably important in the real-time kinematic GPS navigation and positioning. Two kinds of GPS broadcast ephemeris parameters and their user algorithms are introduced in the last GPS interface specification. In this paper, the two algorithms are compared to provide some reference for the broadcast ephemeris parameter research or design. Firstly the new GPS broadcast ephemeris parameters and their user algorithms are briefly introduced, and the differences between the new and old algorithms are analyzed and it is found that the distinctness of the two user algorithms is consistent with those of the broadcast ephemeris parameters. Then the partial derivatives of the satellite position vector to the new GPS broadcast ephemeris parameters are presented based on the calculated expression of the satellite position, which is compared with those of the old GPS broadcast ephemeris parameters. Finally a set of simulation data is used to test and compare the new and old GPS broadcast ephemeris parameter algorithms. Calculation results show that the orbit characters of the MEO satellite can be accurately described by the two kinds of GPS broadcast ephemeris parameters, and the precision losses of the two fitting algorithms are almost several centimeters.
Research on Method to Improving Reliability of In-Orbit Satellite by Failure Mode Avoidance
YANG Tianshe, XI Zheng, LI Jisheng, HUANG Yongxuan
2006, 26(5): 388-393. doi: 10.11728/cjss2006.05.388
Reliability is one of the most important topics researched in Systems Engineering. Due to the peculiarity of satellites and their operating environment, it is hard to use probability or statistic methods for the study of reliability engineering of satellites. To find reasonable methods to improve reliability of satellites is essential in aerospace applications. There are several kinds of method to improve reliability of satellites, robust parameter design and operating windows methods are two of them. One of a new method for improving in-orbit satellites' reliability, Fault Mode Avoidance (FMA), is proposed and applied to improve reliability of satellites in this paper. One-Side and Two- Side failure modes of satellites, such as prediction of status space of failure mode, separation of failure mode, etc., are identified, and mathematic definitions and avoidance procedures of the failure modes are given. Several failure-mode-avoidance strategies are designed, and relative cases of the strategies are also shown.
Optimal Multi-Model Merging Method for Integrative Satellite Precise Orbit Determination Based on GEOSTAR System
WANG Jiongqi, ZHOU Haiyin, WU Yi, ZHAO Deyong
2006, 26(5): 394-402. doi: 10.11728/cjss2006.05.394
Abstract(1829) PDF 1586KB(1147)
Considering the complexity and inaccuracy of the dynamic model for satellite and the fact that parameters to be estimated in orbit determination are correlated temporally with each other, an optical multi-model merging method for integrative satellite precise orbit determination based on GEOSTAR system is proposed. The B-spine function with knots-free is adopted to de- scribe the motion state of a satellite and thus to realize the reduction the error of the dynamic model. Combining the bi-satellite distance observation model, the precise trajectory determination process can be transformed into a nonlinear optimization problem of the multi model merging with the parameters of orbit spine expression coefficients and observation system error coefficients. By introducing the model structure to determinate the selection rule of optimal merging weight and adopting the nonlinear optimization method under LSE rule to search the optimal spine knots dis- tribution, the optimal estimation for the parameters to-be-estimated can be obtained, and the more precise determination of the LEO can be completed. The theoretical analysis and simulation show that this method is more effective, not only in increasing the ultimate precision of satellite state, but also in making the structure of state estimation more robust.
Attitude Control of Space Robot System With Dual-Arms by Optimal Motion Planning
TANG Xiaoteng, CHEN Li
2006, 26(5): 403-408. doi: 10.11728/cjss2006.05.403
Abstract(1949) PDF 3124KB(1420)
The optimal nonholonomic motion planning for free-floating space robot system with dual-arms is discussed. Based on the linear and angular momentum conservations of the system, the system state equations for control design are established, so the nonholonomic motion planning objective of attitude control for space robot system is transformed as the solution of a canonical nonlinear control problem. The optimal control scheme for the proposed system is studied, and a numerical algorithm for computing approximate optimal control of the system is developed. The optimal motion planning approach proposed above possesses the advantages of obtaining the desired angles of the base's attitude and arms' joints only by controlling the arms' joints motion. A planar free-floating space robot system with dual-arms is simulated to verify the proposed approach.