2012 Vol. 32, No. 2

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Magnetopause Location and Shape Under Extreme Solar Wind Conditions
DING Kai, HUANG Zhaohui, WANG Chi, LIU Huilian
2012, 32(2): 161-169. doi: 10.11728/cjss2012.02.161
Abstract(2947) PDF 989KB(1611)
Abstract:
Based on the 3D global MHD numerical simulation data under extreme solar wind conditions, a dynamic 3D asymmetric magnetopause model under extreme solar wind conditions is developed. This magnetopause model parameters are fitted by the Levenberg-Marquart method and this magnetopause model has the ability to describe the saturation effects of the solar wind dynamic pressure Bd on the flaring of the magnetopause, the saturation effects of the interplanetary magnetic field (IMF) Bz on the subsolar standoff distance, the magnetopause indentation in the cusp region, the magnetopause asymmetry and the movement of magnetopause indentation center. On the basis of this model under extreme solar wind conditions, the subsolar point decreases with increasing Bd and increasing Bd causes the decrease of the magnetopause size but almost keeps the magnetopause shapes self-similar; with increasing southward (IMF) Bz, the subsolar point decreases slightly, the flaring of the magnetopause decreases and magnetopause indentation center moves towards lowlatitude. Through analysis of the solar storm on August 1, 2010, it is found that this magnetopause model can describe the global magnetopause location and shape under extreme solar wind conditions.
Application of ADER Scheme in MHD Simulation
ZHANG Yanyan, FENG Xueshang, JIANG Chaowei, ZHOU Yufen
2012, 32(2): 170-781. doi: 10.11728/cjss2012.02.170
Abstract(2475) PDF 388KB(1286)
Abstract:
The Arbitrary accuracy Derivatives Riemann problem method (ADER) scheme is a new high order numerical scheme based on the concept of finite volume integration, and it is very easy to be extended up to any order of space and time accuracy by using a Taylor time expansion at the cell interface position. So far the approach has been applied successfully to flow mechanics problems. Our objective here is to carry out the extension of multidimensional ADER schemes to multidimensional MHD systems of conservation laws by calculating several MHD problems in one and two dimensions: (ⅰ) Brio-Wu shock tube problem, (ⅱ) Dai-Woodward shock tube problem, (ⅲ) Orszag-Tang MHD vortex problem. The numerical results prove that the ADER scheme possesses the ability to solve MHD problem, remains high order accuracy both in space and time, keeps precise in capturing the shock. Meanwhile, the compared tests show that the ADER scheme can restrain the oscillation and obtain the high order non-oscillatory result.
Energetic Neutral Atom Imaging of the Earth Ring Current During Magnetic Storms—Comparison Between Simulation Results and Observation
CHEN Zhiqing, SHEN Chao, LU Li, S. McKenna-Lawlor, LIU Zhenxing
2012, 32(2): 182-190. doi: 10.11728/cjss2012.02.182
Abstract(2892) PDF 1330KB(1164)
Abstract:
Based on an analytical ion model for the ring current, in conjunction with the Chamberlain exosphere density model, Energetic Neutral Atom (ENA) images were calculated for the magnetic storm occurred in November 2004. It was shown that the simulated ENA images differ from images recorded by the Energetic Neutral Atom Detector Unit (NUADU) instrument aboard TC-2 of Double Star mission in terms of azimuth/magnetic Local Time (MLT) distribution, altitude/latitude distribution and energy spectral distribution. If the determiner of asymmetry of the ring current and azimuth of flux maximum can be selected according to evolvement of storms, and more emphasis be placed on density of low altitude exosphere or neutral atoms other than H be taken into account, the ion model is hopeful to produce more precise ring current ion distributions and ENA images. In addition, the ion spectrum at the injection region is expected to be revised and change of ratio of different ion species should be taken into account in order to get better simulation results.
Dust Acoustic Wave in Dusty Plasmas With Streaming Ions Under Ultraviolet Irradiation
REN Liwen, WANG Chi
2012, 32(2): 191-196. doi: 10.11728/cjss2012.02.191
Abstract(2297) PDF 164KB(1267)
Abstract:
The reductive perturbation method is applied to investigate the dust acoustic soliton in dusty plasmas with streaming ions under ultraviolet irradiation theoretically and numerically. The self-consistent dust charge variation is taken into account. It is shown that the ultraviolet irradiation can significantly lower the magnitude of the dust negative charge, and ion streaming velocity firstly raise the magnitude of the dust negative charge and then lower it. With the growth of (Ultraviolet) UV photo flux or ion streaming velocity, the phase velocity and width of the solitary waves decrease, whereas its amplitude increases.
Modified Two Dimensional Third-order Semi-discrete Central-upwind Scheme
HOU Tianxiang, JI Zhen
2012, 32(2): 197-203. doi: 10.11728/cjss2012.02.197
Abstract(2342) PDF 604KB(1048)
Abstract:
The semi-discrete central-upwind scheme is a new Godunov type numerical method which is developed in 1990s. The scheme is widely used in the computational fluid dynamics and its advantages include the simple calculation process, the high calculation precision and so on. But for the third-order scheme, the positivity of the weight function and the non-oscillation of the WENO type reconstruction function in every direction cannot be preserved in two dimensional problems. In this article, a simple, direct modification is taken to the weight function of the two dimensional third-order semi-discrete central-upwind scheme. The modified weight function will keep the positivity all the time while the accuracy of the semi-discrete central-upwind method is preserved. The revised scheme still has the advantages of central-upwind schemes and it keeps the non-oscillation of reconstruction. To explore the potential capability of application of this reformation of weight function, two Magnetohydrodynamics (MHD) problems are simulated. In simulations, the third order Runge-Kutta method is used to solve the time evolution and the divergence of magnetic field was calculated by fourth-order Lax-Wendroff (L-W) scheme. All the numerical results demonstrate the modified scheme can solve the MHD equations stably, get high resolution and non-oscillatory results, keep the positivity of the weight function and the reconstruction is non-oscillatory in each direction.
Forecasting of Ionospheric TEC One Hour in Advance by Artificial Neural Network
WENG Libin, FANG Hanxian, MIAO Ziqing, YANG Shenggao
2012, 32(2): 204-208. doi: 10.11728/cjss2012.02.204
Abstract(3268) PDF 490KB(1436)
Abstract:
A handy method of forecasting the ionospheric TEC one hour ahead by Artificial Neural Network (ANN) is presented in this paper. Considering of the practical application, the observations of TEC are used as inputs without any other data. The input parameters are the present observation of TEC, the first difference and relative difference of TEC, and the local time. The output is the TEC one hour ahead. Ionospheric TEC data evaluated from GPS measurements at Xiamen receiving station is used to checkout the forecasting method. The relative error is 9.3744%, and the cross correlation coefficient between the observed and forecast TEC values is 0.96678. The accuracy rate of relative error less than 15% is 79.59%, during the geomagnetic storms, but 98.81% for the quiet or moderate geomagnetic conditions. These conclusions suggest that the value of forecasting is very the geomagnetic level. It is shown that the Artificial Neural Network is promising in forecasting of ionospheric TEC one hour ahead.
Ionospheric Refraction Correction Based on Spatial Statistic for China Region
HUANG Zhi, YUAN Hong
2012, 32(2): 209-215. doi: 10.11728/cjss2012.02.209
Abstract(2234) PDF 648KB(1113)
Abstract:
Considering the particularity of ionosphere over China and scattered GPS stations in the west, ionospheric refraction correction technologies was explored to provide accuracy data for the single-frequency users of the navigation positioning and remote sensing systems based on satellite. Employing variogram and ordinary Kriging as main tool, this paper elaborated the main idea of ordinary Kriging ionospheric delay correction. Exponential model that is possibly close to the experiment variogram was established respectively considering the quiet and stormy cases. This paper discussed in detail the precision of SBAS ionosphere correction for China region using dual GPS data from Chinese crust deformation monitoring net. Also, result from Kriging is compared with that from planar distance interpolation. The relevant results reveal that Kriging method can improve the accuracy of ionosphere correction and guarantee the integrity of system especially for scattered sample in the cover region.
Variations of Thermosphere Density Based on Joint Analysis of In-Situ Measurement Data From Shenzhou Spacecrafts
SUN Lilin, QIN Guotai, ZHU Guangwu
2012, 32(2): 216-222. doi: 10.11728/cjss2012.02.216
Abstract(1953) PDF 288KB(1435)
Abstract:
Based on the measurements made by Atmospheric Density Detectors (ADDs) onboard Chinese spacecraft Shenzhou 2-4, the variations of thermosphere density are revealed. During the quiet period, the density at spacecraft altitude of 330～410km exhibited a dominant diurnal variation, with high value on dayside and low value on nightside. The ratio of the diurnal maximum density to the minimum ranged from 1.7 to 2.0. The ratio shows a positive correlation with the level of solar activity and a negative correlation with the level of geomagnetic activity. When a geomagnetic disturbance comes, the atmospheric density at the altitude of 330～410km displayed a global enhancement. For a strong geomagnetic disturbance, the atmospheric density increased by about 56%, and reached its maximum about 6～7 hours after the geomagnetic disturbance peak. The density asymmetry was also observed both in the southern and northern hemisphere during the geomagnetic disturbance peak.
Study on O2-supply Characteristics of Azolla in Controlled Ecological Life Support System
CHEN Min, DENG Sufang, YANG Youquan, HUANG Yibin, LIU Zhongzhu
2012, 32(2): 223-229. doi: 10.11728/cjss2012.02.223
Abstract(2368) PDF 590KB(1142)
Abstract:
In this study, we try to investigate the O2-supply characteristics under manned condition in order to lay a foundation for carrying out Azolla biological component systematical and general ground simulation experiment and space application. A closed test cabin of Controlled Ecological Life Support System and Azolla wet-culturing devices were built to measure the changes of atmospheric O2-CO2 concentration inside the cabin under “Azolla-fish-men” coexisting condition. The results showed that, O2 consumption amount per unit weight of fish is 0.0805～0.0831L·kg-1·h-1, the CO2 emission amount is 0.0705～0.0736L·kg-1·h-1. Which of trial volunteers is O2 19.71L·h-1 and CO2 18.90L·h-1 under 7000～8000 lx. Artificial light, human and fish respiring and Azolla photosynthetic O2-releasing tend to achieve O2-CO2 homeostasis inside the cabin. Enhancing atmospheric CO2 concentrations in the cabin obviously promoted Azolla group net photosynthesis efficiency. This shows that Azolla has strong photosynthetic O2-release ability, which equilibrates the O2-CO2 concentration inside the cabin in favor of human survival, and then verifies the prospect of Azolla in space application.
Analysis of Seed Development of Arabidopsis Plants Under a 3D Clinostat Rotated Condition
XU Guoxin, ZHANG Yue, WEI Xiaojing, ZHENG Huiqiong
2012, 32(2): 230-237. doi: 10.11728/cjss2012.02.230
Abstract(2684) PDF 1366KB(1700)
Abstract:
Gravitropism is an important physiological response and an essential mechanism for plants to maintain the normal growth and development on earth. In the life cycle of higher plants, seed development is a key process, but whether gravity can affect the development of seeds has not been confirmed. In this study, the development of siliques and seeds of Arabidopsis under the 3D clinostat rotated condition was analyzed to examine whether seed development including formation of embryos and the activities of metabolism is affected by the altered gravity condition. Our results showed that in the 3D clinostat rotated treated Arabidopsis plants, the morphology of siliques showed an irregular curvature, and the cell division and elongation of suspensor were inhibited. The content of soluble carbohydrates and starch in the young and mature seeds obviously increased, while the content of salt soluble protein decreased. In addition, developing seeds at globular stage are most sensitive to the 3D clinostat rotated treatment with the inhibition of cell division and elongation of the suspensors. Suspensors are important for the transportation of nutrients into embryos and abnormal development of suspensor under the clinostat rotation condition might cause seed abortion.
Orbit Design for Responsive Space Using Multiple-objective Evolutionary Computation
FU Xiaofeng, WU Meiping, ZHANG Jing
2012, 32(2): 238-244. doi: 10.11728/cjss2012.02.238
Abstract(2107) PDF 217KB(2075)
Abstract:
Responsive orbits have exhibited advantages in emergencies for their excellent responsiveness and coverage to targets. Generally, there are several conflicting metrics to trade in the orbit design for responsive space. A special multiple-objective genetic algorithm, namely the Nondominated Sorting Genetic Algorithm Ⅱ (NSGAⅡ), is used to design responsive orbits. This algorithm has considered the conflicting metrics of orbits to achieve the optimal solution, including the orbital elements and launch programs of responsive vehicles. Low-Earth fast access orbits and low-Earth repeat coverage orbits, two subtypes of responsive orbits, can be designed using NSGAⅡ under given metric tradeoffs, number of vehicles, and launch mode. By selecting the optimal solution from the obtained Pareto fronts, a designer can process the metric tradeoffs conveniently in orbit design. Recurring to the flexibility of the algorithm, the NSGAⅡ promotes the responsive orbit design further.
Multi-mode Ensemble Visualization Demo System for Space Weather
LI Fangfang, JIANG Xiujie, LIU Cheng, CHEN Zhimin
2012, 32(2): 245-250. doi: 10.11728/cjss2012.02.245
Abstract(2524) PDF 508KB(1252)
Abstract:
Integration of space weather modes is the basis of operational space weather forecasting. The software system of visualization demo in integration of space weather modes is one of the significant research issues. There are a great deal of space weather modes with diverse elements and complex models, and there are differences in modes’ visualization forms and methods. Combined with characters of current space weather modes in China, the article constructs a multi-mode ensemble visualization demo system with good compatibility and high extensibility, which integrates visualization for most of the current space weather modes. A method of spatial data management is proposed. Based on the OpenGL and Visual C++ software platform, the system fundamentally implements the visualization integration of space weather modes by dynamic loading.
CSP Model and Algorithm on Task Allocation for Earth Observation DSS
GAO Li, LI Zhimeng
2012, 32(2): 251-256. doi: 10.11728/cjss2012.02.251
Abstract(2346) PDF 403KB(1075)
Abstract:
With the vigorous development of small satellite technology, there is an increasing desire to use multiple, highly autonomous, earth bservation small satellites working together to complete more complicated earth observation missions through autonomous collaboration. Distributed Satellites System (DSS) composed by several small satellites is envisioned in the near future because of its capability of higher performance, lower cost, better fault tolerance, reconfigurability and upgradability. Considering the characteristics of autonomous operation cooperatively for DSS in future, the task allocation becomes a very important process in the operation. In the paper, with the principle of lowest general energy-consumption for completing observation task, a model for Constraint Satisfaction Problem (CSP) on task allocation was put forward by analyzing the features of observation task for DSS. Based on it, citing contract net protocol in MAS theory, an algorithm was presented to solve the model and an example of the earth observation satellites was given to validate the model and algorithm at last.
Design and Implementation of Full-link Simulation System of Space-to-ground Optical Communication
CUI Minglu, WANG Zhiqiang, LIU Wei
2012, 32(2): 257-264. doi: 10.11728/cjss2012.02.257
Abstract(2538) PDF 682KB(1184)
Abstract:
The existing designs of space-to-ground single-photon communication have the defect that the system-level parameters are difficult to be given, due to the adoption of the analysis based on subsystems. For the purpose of combining all subsystems and key system-level parameters’ influence, full-link simulation method is introduced. A space-to-ground optical communication full-link simulation system based on OMNeT++ is constructed to perform the APT (Aiming, Pointing, Tracking) and single-photon communication experimentation by Monte-Carlo method. The simulation system has the abilities of simulating correlations between subsystems, reflecting the key parameters’ influence on the whole system, and estimating the performance of a true system due to its full-link character. The simulation system is significant to design and optimize true space-to-ground optical communication systems.
Study on Assessment Method of Reliability of Spaceflight Electronic Device
SUN Peng, ZHAO Yang, DONG Haiping
2012, 32(2): 265-259. doi: 10.11728/cjss2012.02.265
Abstract(2534) PDF 400KB(2021)
Abstract:
A Bayesian reliability assessment method for spaceflight electronic device is put forward. The method combines the reliability information of the whole system and its subsystems. At first, the maximum entropy method is used to syncretize reliability information of subsystems; then the calculation formulas of moments of system reliability are deduced from reliability moments of subsystems and inheritance factor is determined and mixed Beta distribution is built; finally, the posterior distribution is used to assess system reliability. With the new method, the reliability of a spaceflight electronic device is evaluated to reach 0.9991 under the confidence level 0.70 with 240 whole system tests which is one-fifth of system tests needed by the classical method. It is feasible to use the new method to assess reliability of spaceflight electronic device.
SEU-tolerant System Design of SRAM FPGA Based on Scrubbing in Aerospace
MA Yin, AN Junshe, WANG Lianguo, SUN Wei
2012, 32(2): 270-276. doi: 10.11728/cjss2012.02.270
Abstract(3184) PDF 573KB(2151)
Abstract:
Aerospace and extra-terrestrial applications on SRAM FPGA are sensitive to SEU which might result in information loss or functional interruption. In this paper, a detailed introduction to TMR and Scrubbing, which are the significant techniques of this design, was given; then, a highly reliable fault-tolerant system based on TMR, Scrubbing and Reload rules was implemented. An anti-fuse FPGA periodically scrubbed the configuration bitstream of SRAM FPGA in milliseconds level, and both FPGAs implemented triple module design redundancy. This fault-olerant design has been adopted in an actual spacecraft electronic system, which can make reference to the design of highly reliable electronic systems.
A General IF Radar Echo Simulator Based on PC and FPGA
CHEN Xiuwei, ZHANG Yunhua, ZHANG Xiangkun
2012, 32(2): 277-283. doi: 10.11728/cjss2012.02.277
Abstract(2333) PDF 623KB(1111)
Abstract:
A general radar echo simulator hardware architecture based on PC and FPGA is proposed, which is a kind of PC+FPGA+D/A simulation system, and the simulator architecture has come to be a good choice with the development of PC technique and advanced chip field. The system is mainly based on a kind of PCI board which includes Virtex-4 FPGA and high performance D/A convertor with latest techniques and flexibility. Compared with traditional instruments, it is scalable, programmable and suitable for upgrading. The developed simulator has been tested and results show that the technical performance can meet the requirements of our application.
Simulation to Exploring Boom of TC-2 Satellite in Technical State Improving Design
YANG Xuan, YANG Hua, QIAO Zhihong, REN Weijia
2012, 32(2): 284-288. doi: 10.11728/cjss2012.02.284
Abstract(2081) PDF 748KB(1379)
Abstract:
A highly reliable two-segment deployable boom has been developed and manufactured for the Double Star Program. Two spacecrafts, one for equatorial, the other for polar orbit are equipped each with two mechanisms. One boom deploys two flux-gate magnetometers, the other a search coil magnetometer. The paper discusses the structure and mechanical problems of TC-2 satellite’s exploring booms in technical state improving design, and analyzes the mode, structure static strength as well as the clamp expanding process of exploring boom in TC-2 satellite. Results show that the boom clamp’s frequency only had small change after altering the pyrotechnical rod cutter and it would not have influence on the satellite’s frequency. The improved clamp can bear dynamic load, and its maximal stress and strain are all within the allowed range of material. Moreover, the clamps do not intervene with other parts when they are deployed, which can meet the satellite’s request.
Research of Image Compression Algorithm for Sounding Rocket
LI Guoqing, LIU Bo, YU Shiqiang
2012, 32(2): 289-297. doi: 10.11728/cjss2012.02.289
Abstract(2188) PDF 633KB(1137)
Abstract:
According to the requirements of Sounding Rocket Image System, an image compression algorithm based on Discrete Wavelet Transform coding-MSPIHT Adaptive Differential Arithmetic Coding for image (MADAC), is proposed. In the algorithm, the Modified SPIHT (MSPIHT) method is used to scan and quantize the parameters of the Wavelet Transform and an adaptive differential arithmetic algorithm is designed to code the data after the quantization stage in the entropy stage. Result of experiments shows that the performance of MADAC is satisfying, and the adjustable image resolution, frame rate and compression ratio required by the Sounding Rocket Image System could be realized through MADAC. All the three stages of MADAC are easy to be implemented on hardware.
Destriping for TDI-CCD Remote Sensing Images
ZHAO Bianhong, HE Bin, YANG Lihong, TAO Minghui, REN Jianyue
2012, 32(2): 298-304. doi: 10.11728/cjss2012.02.298
Abstract(2679) PDF 804KB(1185)
Abstract:
Based on the characteristic of striping noise in TDI-CCD images, a new destriping noise technique which combines FFT with wavelet transform to search the frequency point of the striping noise is presented. The improved notch filter is selected to eliminate the striping noise. In addition, an improved threshold function based on lifting wavelet transform is used to eliminate the stripes. Experiment shows that the method of improved notch filter is superior to the improved threshold function while the improved threshold function is superior to the hard and the soft threshold function. After destriping using the improved notch filter, the quality of image is enhanced. The PSNR of the destriping image processed by improved notch filter is increased to 46.4181dB and the NMSE is decreased to 0.00007. Compared to the methods of threshold function based on lifting wavelet transform, the PSNR of destriped image is improved by 3～4dB and the NMSE is reduced by 0.00007～0.00011. The method of improved notch filter which combined FFT with wavelet transform and the methods of threshold function based on lifting wavelet transform can eliminate the striping noise while preserve the characteristic of the original image, so the several methods are of feasibility.

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