2017 Vol. 37, No. 2

Display Method:
Rapid and asymmetric response of the Earth's bow shock: multipoint observations
LIU Bing, DUNLOP M W, CAO Jinbin, LAVRAUD B, LI Liuyuan, YANG Junying
2017, 37(2): 129-139. doi: 10.11728/cjss2017.02.129
We analyze observations of three bow shock crossings which occurred during 2007, using upstream data from STEREO A/B, ACE and WIND, combined with multi-point THEMIS and Cluster data, and TC-1 data located near noon. During the crossing of 7 May 2007, we find that following a rapid reduction in solar wind ram pressure and subsequent pressure pulse seen by ACE and WIND upstream, the bow shock responds asymmetrically from dawn to dusk. Cluster data on the dawn-side suggest the bow shock is significantly flared and responds rapidly to the pulse arrival, while TC-1 at noon, and THEMIS on the dusk-side, are well matched to the model bow shock, but show a delayed response. The crossings observed on 21 May and 2 June show contrasting response matching the model boundary for northward Interplanetary Magnetic Field (IMF). The IMF and solar wind plasma data suggest that the bow shock crossing at dawn-dusk side and subsolar point were mainly caused by large and smaller scale features of the solar wind ram pressure rise rather than the influence of IMF.
Case study on nightside polar ionospheric convection response to interplanetary shock (in Chinese)
LIU Qiongqiong, HU Hongqiao, LÜ Jianyong, LIU Jianjun, LIU Ruiyuan
2017, 37(2): 140-150. doi: 10.11728/cjss2017.02.140
An interplanetary shock event on 14 July 2012 is studied using observations with Super Dual Aurora Radar Network (SuperDARN), northern hemispheric IMAGE magnetometer chain and All-sky Aurora Imagers at Zhongshan station, Antarctica. At 18:10UT, an interplanetary shock struck the magnetosphere and induced geomagnetic sudden commencement. Observations of SuperDARN present that the ionosphere convection of northern hemisphere was enhanced obviously. The Hankasalmi radar, whose field of view covers the Yellow River station, found that the ionospheric F layer was severely disturbed, e.g. the echoes number increased obviously and inversion phenomenon of local ionospheric convection speed emerged from 18:10UT to 18:33UT. There are three irregularities in F layer measured by Hankasalmi radar and their speeds in line-of-sight reached 600m·s-1 after 18:33UT. Kerguelen radar around Zhongshan, conjugating with the Yellow River station, observed that the number of the echoes had little change and the echoes are mainly from E layer and there are almost no echoes from F layer. However, the All-sky Imagers at Zhongshan station observed the enhancement of aurora activity. The observation difference of northern and southern hemispheres nightside ionospheric responses are mainly because of that they were at polar night and polar day respectively.
Inversion of the Ionospheric Current Density by Multi-point Synchronous Magnetic Field Measurements
GAO Rui, LI Lei, ZHANG Yiteng, LIU Xuewang, LI Mingtao
2017, 37(2): 151-157. doi: 10.11728/cjss2017.02.151
Compared with the traditional single-point measurements, multi-point synchronous magnetic field measurements can give more accurate space current density because multi-point measurement can eliminate the temporal change in the magnetic field. Based on the current density inversion method for multi-point magnetic field measurements, the inverse current density and its error is simulated, and the effects of some factors, on the space current density inversion are analyzed. These factors conclude the number of satellites, satellite formation configuration, satellite positioning precision, satellite attitude determination error, magnetic field measurement accuracy, external magnetic field intensity, and external current density and so on. Simulation results show that 5-point measurements are better than 4-point measurements, and satellite attitude determination error, satellite formation configuration and external magnetic field intensity are main factors causing the error of current density. According to the simulation, the maximum error of current density near the equator is about 24% as the attitude determination error is 0.001° and the satellite formation scale is about 100km.
Multi-frequency Doppler Fast Detection and Analysis of Meso-micro Scale Ionospheric Disturbances
HE Dejiang, ZHU Zhengping, LAN Jiaping, NING Baiqi, HU Lianhuan
2017, 37(2): 158-167. doi: 10.11728/cjss2017.02.158
Measuring the HF Doppler frequency shifts of ionospheric echoes is one of the important ways to study ionospheric disturbances. We use the real-time detection method based on measuring the phase-change rate of single frequency signals, and obtain continuous high-precision multi-frequency Doppler ionograms to achieve fast detection and study of meso-micro scale ionospheric disturbances. This method is applied to the multi-frequency detection system which is jointly developed by the Chinese Academy of Sciences and South-Central University for Nationalities. It is verified that the Doppler resolution obtained from this platform can be up to 0.039Hz and the minimum ionogram period is less than 1 minute. We collect a long-time raw data of the ionosphere based on this new detection method and platform in Wuhan observatory. Through the way of acquiring high-precision Doppler frequency shifts and the method of inversing the normal velocity of electron concentration isosurface, the Doppler ionograms and vertical disturbed velocity of O waves are obtained. Furthermore, the real-time changes of ionospheric disturbances with time and space are deduced. By the spectrum analysis on these time domain signals, preliminary results show that these disturbances are mainly mesoscale TIDs motivated by the Polar activities which often appear in winter in central China. This paper also compares the three commonly used inversion methods. The results show that the ionospheric disturbances have almost the same change trends. It indicates that the observation data and the research methods are reliable and stable, which provides an important basis for observing and researching the multi-frequency and multi-point propagation characteristics of ionospheric disturbances.
TIEGCM Ensemble Kalman Filter Assimilation Model Design and Preliminary Results
ZHANG Yanan, WU Xiaocheng, HU Xiong
2017, 37(2): 168-176. doi: 10.11728/cjss2017.02.168
Abstract(1263) PDF 1426KB(1224)
By using the parameterized ionosphere model TIEGCM as the background model, and based on the COSMIC observations, the global ionospheric electron density assimilation model is established using ensemble Kalman filter. Result shows that this model can effectively assimilate the observations into background model and acquire three-dimensional ionospheric electron density. By comparison to the background, the error between analysis and observations decreases significantly. The Root Mean Square Error (RMSE) of NmF2 decreases by about 60% for observations with assimilation, and 20% for observations without assimilation. The RMSE of hmF2 does not get improvement except for mean error. The results of Simultaneous Assimilation (SA) and Batches Assimilation (BA) are compared for this case. The time that the two methods spend in assimilation is about 6 to 7 minutes, which does not differ very much. SA needs nearly 8GB storage while BA needs less than 2GB. The statistic of electron density error shows that they nearly acquire the same mean error, but the SA gets relative better improvement in RMSE above 250km height.
Seasonal Variation of Atmospheric Temperature and Gravity Wave Activity over Beijing Area
GUO Wenjie, YAN Zhaoai, HU Xiong, GUO Shangyong, CHENG Yongqiang, HAO Wenze
2017, 37(2): 177-184. doi: 10.11728/cjss2017.02.177
Abstract(1016) PDF 2761KB(1113)
By using Rayleigh lidar data, the seasonal variations of atmospheric temperature and gravity wave activity at 30~70km height over Beijing area are analyzed. Results show that the atmospheric temperature has an obvious annual cycle variation. The highest temperature in the stratopause appears in June or July, which is about 270K. The lowest temperature at 70km height of the middle layer also occurs in June or July, which is about 200K. Taking the data of 14 October 2014 as an example to analyze the potential energy density of gravity wave, we find that dissipation exists in the potential energy of gravity waves under 50km height, while gravity waves propagate up with no dissipation over 50km height. Using the average potential energy density at 35~50km height, the seasonal variation of the gravity waves activities intensity is analyzed. The gravity waves activities have an obvious annual cycle. The average potential energy density is 18J·kg-1 and 8J·kg-1 in winter and summer respectively. The gravity waves activities intensity in winter are about two times of that in summer. In addition, the variation of gravity waves potential energy density with height in spring, summer, autumn and winter are analyzed. The analysis shows that the potential energy density of gravity waves is changing with different seasons and heights.
Microbial Diversity Analysis in Spaceflight AIT Center
YUAN Junxia, YIN Hong, ZHAO Biao, ZHANG Lantao, QU Xi, XU Kanyan
2017, 37(2): 185-191. doi: 10.11728/cjss2017.02.185
Abstract(1202) PDF 986KB(1139)
The assembly of spacecraft in clean room environment is essential for the prevention of forward contamination. In this study, both high-throughput sequencing and culture-based method are used to study the microbial community structure and diversity in the AIT (Assembly, Integration and Test) center of the spaceflight. The result of high-throughput sequencing analysis show that in the AIT center the dominant genus of airborne bacteria is Bacillus (78.47%±1.59%), and the dominant fungi is Tremellales (8.97%±0.93%). However, culture-based analysis indicates that the Staphylococcus is the dominant bacteria, and no fungal colony is observed in the AIT center. The microbial diversity is evaluated by chao1 index, Simpson index and Shannon index, and the results show that the bacterial diversity level is higher than that of fungal in the AIT center.
Simulation of Microwave and Sub-millimeter Wave Radiation from 1 to 3000GHz of Planetary Atmosphere
FU Jia, WANG Zhenzhan
2017, 37(2): 192-201. doi: 10.11728/cjss2017.02.192
Abstract(1023) PDF 4876KB(1418)
In order to simulate the radiative transfer characteristics of planetary atmosphere in the microwave and sub-millimeter wave bands, the absorption coefficient from 1 to 3000GHz of the gases in planetary atmosphere are calculated by using line-by-line integration method. Based on the parameters of gas molecules in HITRAN database, such as the transition frequency, line strength and so on, the absorption feature of each gas molecule is simulated and compared with the common atmosphere radiative transfer model in microwave and sub-millimeter wave bands. As an example, the radiation transport characteristics of Earth's atmosphere are analyzed, and the atmospheric radiation brightness temperature of different frequency band using limb sounding method is simulated using the radiative transfer equation. The results can provide the model and theoretical basis for atmospheric composition detection simulation, the selection of detection frequency band and the retrieval of atmosphere profiles of Earth and other planets.
Collision avoidance strategies based on Gauss pseudospectral method (in Chinese)
AN Xibin, HE Bing, CHEN Fugui, LIU Bingqi, LIN Haoshen
2017, 37(2): 202-206. doi: 10.11728/cjss2017.02.202
In order to ensure the safety of active satellite, it is necessary to perform an orbit maneuver before the collision between space debris and satellite to protect satellite from space debris. The strategy of continuous-thrust is chosen for avoiding collision. The collision avoidance process is converted to optimal control problem with complicated constraints, while Gauss pseudospectral method is used to solve this problem and the result meets the requirements of avoidance. The simulation results show that the new method can decrease the consumption of fuel. It is significant for avoiding collision between space debris and the satellite.
Simulation Study on GRO and LRO Events
WANG Shuzhi, LIU Congliang, ZHU Guangwu, BAI Weihua, DU Qifei, SUN Yueqiang, XIA Junming, MENG Xiangguang, WANG Xianyi, ZHAO Danyang, WANG Dongwei, CAI Yuerong, WU Di
2017, 37(2): 207-213. doi: 10.11728/cjss2017.02.207
Abstract(1266) PDF 3426KB(1333)
Combining the GRO (Global Navigation Satellite System Radio Occultation) and LRO (Low Earth Orbit Radio Occultation) techniques to probe the Earth's atmosphere is a main development direction of RO (Radio Occultation). In this study, the mathematical criteria of a RO event have been described. Then the effects of the main orbit parameters of LEO satellite on the RO events amount and their global distribution have been discussed by a simulation study. The results showed that:the lower the LEO satellite orbit is, the more GRO events are; when the inclination is between 30° and 75°, there are more GRO events and their Earth coverage is higher. The LRO events distribute on the Earth evenly when the LEO-LEO RO satellite set in the polar orbits. This study can provide a scientific reference for GRO and LRO satellite constellation design.
Analysis of the changing regularity of 16-parameter GPS broadcast ephemeris improved parameters (in Chinese)
FENG Laiping, CUI Xianqiang, JIA Xiaolin, RUAN Rengui
2017, 37(2): 214-221. doi: 10.11728/cjss2017.02.214
Abstract(1215) PDF 1830KB(1109)
A new 18-parameter GPS broadcast ephemeris improved on the basis of 16-parameter GPS are introduced in the GPS interface control document issued in 2004. But the improved reasons have not been analyzed. In this paper, the fitting algorithm of 16-parameter GPS broadcast ephemeris is briefly introduced, the differences of the two kinds of GPS broadcast ephemeris parameters are compared, and the change regularity and properties of the improved parameters are analyzed. Calculation results show that the improved parameters of 16-parameter GPS broadcast ephemeris have obvious periodic variation characteristics with a period of about 12 hours and 13.5 days, and the newly proposed 18-parameter GPS broadcast ephemeris can better approach the real orbit of GPS satellites.
Experimental Assessment and Mitigation of Operational Amplifier's SET Effect
CHENG Jia, MA Yingqi, HAN Jianwei, ZHU Xiang, SHANGGUAN Shipeng, CHEN Rui
2017, 37(2): 222-228. doi: 10.11728/cjss2017.02.222
Single Event Transients (SET) of linear device have the characteristics of transience and propagation, which cause great difficulties to fault location and mitigation design for on-orbit electronic systems and devices, and are significant threat to the reliability of spacecraft. To mitigate SET for linear devices, comprehensive experimental assessment on the SET is required, and parameters of the SET in the worst case especially need to be determined. Then specific filtering circuit can be designed according to the worst case parameters of SET and the application circuits. In this paper, SET assessment and mitigation on operational amplifier LM124 which is typically used in spacecraft are investigated. Firstly, SET characteristics of the device are evaluated by pulse laser facility, and the worst SET with duration of 35μs and amplitude of 7.2V are observed. Then, by using Hspice simulation, the SET of LM124 are compared and verified with experimental assessment, and mitigation on the worst SET using different parameters of filter circuits are investigated. Finally, the mitigation on worst SET with the optimized filtering circuit is investigated and verified again using the pulsed laser facility. The work of this paper is useful to investigate and mitigate SET of other linear devices applied in space.
Integrated Design of Payload Based Dark Matter Particle Explorer
DONG Lei, LI Huawang, ZHU Cheng, ZHU Zhencai, CHANG Liang
2017, 37(2): 229-237. doi: 10.11728/cjss2017.02.229
The Dark Matter Particle Explorer (DAMPE) is the first high energy detection satellite in China, and its scientific goal is to find the evidence of dark matter particle existence by investigating the composition and energy spectra of primary cosmic rays, especially for electrons, positrons and gamma rays, over the dynamic range from 5GeV to 10TeV. The DAMPE is composed by BGO calorimeter, plastic scintillation array detector, silicon array detector and neutron array detector, and is the largest payload ratio satellite. This paper introduces the technical schemes of DAMPE, including technical index, orbit, working mode and system composition, and the integrated design of structure, thermal control and EMC in DAMPE.
Analysis of Line-of-sight Measurement Error for Satellite-borne Observation Platform
DING Wenzhe, ZHANG Zhanyue, YANG Hong, CHEN Feng
2017, 37(2): 238-248. doi: 10.11728/cjss2017.02.238
A line-of-sight measurement error modeling and evaluation method based on multi-parameters is studied to analyze the influence of the error sources of the satellite-borne observation platform on the line-of-sight measurement accuracy. Unlike conventional measurement for satellites and space camera, the target imaging model from target position to focal plane and the line-of-sight measurement model for satellite-borne observation platform are constructed on the basis of the satellite, turntable, and camera observation structure. The relationship between the measurement error and the error sources is derived theoretically and a method of error evaluation based on sensitivity analysis is presented. In three axial directions, the influence of the error sources of the satellite-borne observation platform on the line-of-sight measurement accuracy are analyzed. Monte Carlo simulation verified the validity of the theoretical model. The results demonstrate that the line-of-sight measurement accuracy is affected by satellite orbit error, satellite attitude error, load platform angular vibration error, inner frame and outer frame rotation error, image points position quantization error. The method can scientifically evaluate the influence of various error sources on measurement accuracy, and has important application value to the overall design of the satellite-borne observation platform.