2018 Vol. 38, No. 1

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Abstract(1050) PDF 339KB(2161)
2018, 38(1): 7-7.
Relationship of Halo CME and Solar Proton Events ormalsize
WANG Cong, CUI Yanmei, AO Xianzhi, LUO Bingxian, WANG Jingjing, LIU Siqing
2018, 38(1): 9-18. doi: 10.11728/cjss2018.01.009
Abstract(1069) PDF 7542KB(3253)
Coronal Mass Ejections (CME) are an important source of Solar Proton Events (SPE). Their speeds and source region locations have significant effects on SPE productions. In this paper, all halo CME in recent five years are statistically analyzed. The results show that fast halo CME with small angle distances are more likely to produce SPE, especially those halo CME with the speed greater than 1200km…-1 and the angle distance less than 60°. Three fast halo CME without SPE are elaborately studied. The results show that CME's main body moving direction and the variations of interplanetary magnetic fields also have important impacts on SPE emerging. Consequently, in daily operational space environment forecasts, an accurate SPE forecast must take various factors into account, such as CME burst speed, source region location, CME main body ejection direction, interplanetary environment, and so on.
Statistical Study of Axial Orientations of Flux Transfer Events at the Magnetopauseormalsize
LI Zhaoyu, CHEN Tao
2018, 38(1): 19-28. doi: 10.11728/cjss2018.01.019
Flux Transfer Events (FTE) are related to magnetic reconnection. The typical characteristic of FTE is bipolar variation of the field component normal to the local magnetopause. There still exist different views about FTE global topology on the magnetopause. In different models, the FTE structures are either reconnected flux tubes, or magnetic flux ropes formed by multiple X-line reconnection or sheared magnetic loops formed by single X-line reconnection. To infer the global configuration of FTE, a statistical study of axial orientations of 505 FTE observed by Cluster during one dayside magnetopause crossing season is performed. The result shows that most FTE have north-south-orientated axes roughly aligned with the local magnetospheric flux tubes at both the low-and middle-latitude flanks. However, most FTE have dawn-dusk-orientated axes which are more consistent with the single or multiple X-line orientations at high latitude, especially near the cusp. These statistical features will improve our understanding about the global topology of FTE.
Ionospheric currents and nightside ionospheric magnetic fields calculated by TIE-GCM
LIU Xuewang, LI Lei, ZHANG Yiteng, XUE Hongbo
2018, 38(1): 29-36. doi: 10.11728/cjss2018.01.029
In geomagnetic field mapping, the magnetic fields generated by the ionospheric currents are sources of interference that should be removed. In this paper, the ionospheric currents generated by neutral wind, gravity drift and pressure gradient are calculated by Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The global current distribution is used to examine the magnetic field generated by the ionospheric currents at a specific location. The variation of the three components of the magnetic field with latitude has been analyzed. The results show that the current densities in the E layer, especially in the magnetic equator and polar regions, are as high as about 103nA·m-2, while the current densities in the F layer are about 10nA·m-2. The magnetic field between 50°N and 50°S induced by ionospheric currents is about several nT from 22:00LT to 04:00LT in the magnetic quiet day (Kp ≤ 1), and the north-south and radial components of the ionospheric magnetic field are substantially larger than the east-west component. By comparing with CHAMP observation data, it is proven that the TIE-GCM has good performance in calculating ionospheric currents and magnetic fields at low and middle latitudes. However, the results are not very good at high latitudes and TIE-GCM should be improved in order to increase the calculating accuracy.
Effects of Ionosphere Shell Height on Ionospheric Modelingormalsize
LIU Chen, LIU Changjian, BAO Yadong, FENG Xu
2018, 38(1): 37-47. doi: 10.11728/cjss2018.01.037
The spatial-temporal variations of shell height are analyzed by utilizing IRI2012 model. The method for precision evaluation of the ionosphere models based on STEC differences in applications is presented, and the relevant influences of shell height on the positions of Ionospheric Pierce Point (IPP), mapping function, ionospheric modeling, ionospheric elaboration and ionospheric accuracy evaluation are discussed. When satellite elevation cut-off angle is set to be 10°, the shell height has important impact on the above quantities. The maximum deviation in latitude or longitude is about 3.2°. The maximum error of mapping function is about 15.46%. The maximum deviation and practical error are about 9.71%, 3.64% respectively. The maximum error in ionospheric elaborations is about 9.26%, and the maximum error in ionospheric accuracy evaluation is about 9.62%. According to the above results, the following suggestions are given. Firstly, a shell height model and a larger elevation cut-off angle should be adopted to reduce the above errors. Secondly, when a fixed shell height is adopted, the same height should be used in regional ionospheric modeling. Thirdly, the shell height of reference data should be the same to the be-assessed data in accuracy assessment.
Prediction Model for Ionospheric Total Electron Content Based on Deep Learning Recurrent Neural Networkormalsize
YUAN Tianjiao, CHEN Yanhong, LIU Siqing, GONG Jiancun
2018, 38(1): 48-57. doi: 10.11728/cjss2018.01.048
Abstract(1362) PDF 2429KB(1098)
A 24h ahead forecasting model for ionospheric Total Electron Content (TEC) at Beijing station is established based on the deep learning Recurrent Neural Network (RNN) for the first time. The model implementation requires solar 10.7cm flux index, geomagnetic index ap, grid map of TEC, solar wind speed and the southward components of interplanetary magnetic field. The predicting results for Beijing station (40°N, 115°E) show that the Root Mean Square Error (RMSE) of the disturbed ionosphere TEC predicted by RNN model is lower than that of BPNN (Back Propagation Neural Network) model by 0.49~1.46TECU. The forecasting accuracy of ionospheric positive storm by RNN model is increased by 16.8% with solar wind parameters. Furthermore, the RMSE of RNN model of 31 strong TEC storms in 2001 and 2015 are less than those of BPNN model by 0.2TECU, and the RMSE of RNN model is decreased by 0.36~0.47TECU as solar wind parameters are added. The results indicate that RNN model is more reliable than BP model for short-term forecasting of TEC. Moreover, the addition of interplanetary solar wind parameters are helpful for predicting TEC positive storm.
Retrieval Algorithm and Precision Analysis for NmF2 of Nighttime OI135.6nm Emissionormalsize
JIANG Fang, FU Liping, WANG Yongmei
2018, 38(1): 58-64. doi: 10.11728/cjss2018.01.058
The nighttime OI135.6nm airglow is proportional to the square of the maximum electronic density of ionospheric F2 layer (NmF2). Based on the previous studies of the nighttime OI135.6nm airglow radiative and emissive model, the retrieval algorithm of NmF2 derived from nighttime OI135.6nm emission was presented. The column emission rate is calculated for each grid point of the nighttime airglow radiative and emissive model. The electron density profile, O+ density profile, and electron temperature profile are taken from the IRI2000 model, and the neutral components are taken from MSISE90 model. In order to derive the relationship between the OI135.6nm column emission rate and NmF2, the column emission rate is fitted to the square of NmF2 linearly. The ratio of the square of NmF2 to the column emission rate is obtained from the slop of the fitting line, which gives the relationship between NmF2 and the emission. According to the measurements of the OI 135.6nm column emission rate, NmF2 are retrieved. Finally, the error of the retrieval method is analyzed, which provides important theoretical supports for the time and space applicability of the algorithm.
Lidar Observations and Studies of the Lower-triangle Potassium Layer over Beijing ormalsize
WANG Zelong, YANG Guotao, WANG Jihong, JIAO Jing, DU Lifang, XUN Yuchang
2018, 38(1): 65-72. doi: 10.11728/cjss2018.01.065
A special behavior of the potassium layer in the mesopause region has been discovered over Beijing, China (40.4°N, 116.0°E) from two-year long data sets, during November 2010 to October 2011 and May 2013 to April 2014. This peculiar potassium layer is termed as the lower-triangle potassium layer. The peak density of the lower-triangle potassium layer increases gradually and the height of the peak density evidently descends with time. The concentration of the potassium atoms first increases rapidly and then decreases slowly along with the increasing height. When the lower-triangle potassium layer appeared, the column density below 90km increased significantly, but the column density above 90km changed little. Then the whole column density increased obviously. There are the longest occurrence time and the highest occurrence ratio of the lower triangle potassium layer in January, which could be related to seasonal variations of the atmospheric semidiurnal tides. The frequent appearance of the lower-triangle potassium layer has made the average column density and peak density increase by 15.7% and 12.9% respectively, but the centroid height decrease by 0.18km in January. The comparisons between the lower-triangle potassium layer and the sodium layer at the same time and location show that the concentration of sodium atoms had no obvious change when the concentration of potassium atoms increased remarkably. Assuming that there were no special sources injecting into the metal layers, according to the chemical reactions and relevant chemical reaction rates in potassium model and sodium model, it can be speculated that the increasing potassium atoms in the lower-triangle potassium layer were mainly converted from KO2, and partly from KOH.
Comparative Analysis of Space Debris Gaze Detection Based on Two Incoherent Scattering Radars Located at 69°N and 78°N ormalsize
TANG Zhimei, DING Zonghua, DAI Liandong, WU Jian, XU Zhengwen
2018, 38(1): 73-78. doi: 10.11728/cjss2018.01.073
Based on the joint observation of two incoherent scattering radars located at 69°N and 78°N, parameters including the height, radial velocity, Radar Cross-section, and effective diameter etc. are obtained. Statistical analysis on these data is made and conclusions are drawn as follows. The space debris detected by the two radars are distributed at the height from 500 to 1100km and from 1400 to 1600km, but the number of pieces detected by the radar located at 78°N is more than that detected by the radar at 69°N. The radial velocities are almost distributed in -1.5~1.5km…-1 and more of them are negative, which shows that most of the debris move far away from the Earth in this detection. The RCS is about 10-5~10-2m2 and the effective diameter is about 3~10cm at 69°N, and the RCS is about 10-6~10-2m2 and the effective diameter is about 2~6cm at 78°N. The minimum size of space debris detected by the radar located at 78°N is bigger than the one detected by the radar at 69°N, which means that the detection power of the radar located at 69°N is stronger than the radar at 78°N at the same height. Concluding the repeat testing number after setting up reasonable criterion parameters, the two radars located at 69°N and 78°N respectively have 32 and 14 repeat numbers, and 4 repeat numbers overlapped. These results show the good perspective in the fragment cataloging and modeling of the space debris.
Path optimization in the removal progress of multi-debris (in Chinese)
ZHOU Xiuhua, YU Xizheng, WANG Ronglan, ZHOU Binghong
2018, 38(1): 79-87. doi: 10.11728/cjss2018.01.079
In this paper, ant colony optimization algorithm is used to study the path optimization in the removal progress of multi-debris. The modified steepest descent method is used to optimize the time of removing each piece of debris reasonably which further reduces the aggregate requirements of velocity increment. The comparisons with the order of orbit height, inclination or RAAN (Right Ascension of the Ascending Node) indicate that using the order after the optimization of the ant colony algorithm can greatly save the velocity increment. Three groups of debris produced in Chinese activities are chosen for optimization. Results show that the optimized order may be different from three kinds of order mentioned above, and the optimized order can save more velocity increment in the same task time. In addition, the task time also has an impact on the best removal order of debris.
Simplified Calculation Method of Geomagnetic Field Model ormalsize
ZHANG Tao, GAO Dong, ZHENG Jianhua
2018, 38(1): 88-93. doi: 10.11728/cjss2018.01.088
Abstract(1625) PDF 1338KB(5852)
To realize the application of geomagnetic navigation on the low orbit satellite, the complexity, enormous calculation, poor real time ability of traditional Gaussian spherical harmonica function should be solved before being used to calculate the geomagnetic vector. A geomagnetic field approximation function, Geomagnetic Field Approximation Functions (GFAF), is proposed to replace the spherical harmonic function. Dipole model under a pseudo-centers is utilized to replace the main geomagnetic model in GFAF method. And the coefficient of pseudo-center of different latitude-longitude grid is obtained by polynomial fit method. Finally, the geomagnetic field vector of any position can be achieved using different interpolation algorithm. A simulation test is carried out under the condition that the increment of latitude and longitude is 0.5° and the orbital height is from 300 to 500km. The results show that the navigation accuracy of GFAF method is the same to that of geomagnetic field model. However, GFAF method effectively decreases the cost of computing and and improves the calculation efficiency.
Study on Solar Simulator Two-axis Rotation Control Systemormalsize
HU Bing, WANG Lingyun, ZHANG Guoyu, SU Shi, JIANG Wenzhang, YANG Liyan
2018, 38(1): 94-100. doi: 10.11728/cjss2018.01.094
Sun sensor is an important component in the satellite control system. Prior to loading on the star, the sensor needs to be tested in the ground to verify its various function and technical index. Aiming at the ground test equipment of Sun sensor, a two-axis rotation control system of solar simulator was studied. The system includes the yaw and pitch rotary control mechanism, which are mainly used to change the direction of the optical axis of the solar simulator. In the control system, the servo motor is combined with absolute photoelectric encoder. In this paper, the composition and working principle of rotary control system are given, and the factors that can affect the precision of the system and measure its precision through the experiment are analyzed. Experiments show that the angle of rotation of the control system accuracy is better than 0.03°, which can meet the precision index of 0.04° when the design of the ground instrument is put forward.
Study of Dynamics Simulation on Large Space Deployable Membrane Structuresormalsize
ZHANG Hua, LIU Hanwu, LI Dongying, PENG Fujun
2018, 38(1): 101-108. doi: 10.11728/cjss2018.01.101
Space-based Synthetic Aperture Radar (SAR) antenna is focused on high-resolution earth-observing field widely for its special applied purpose. Due to the characteristics of light-weight, large-size and various frame, the large space membrane structure is used for SAR antenna. In order to know its on-orbit dynamics performance, the dynamics model is built, based on the method of temperature-structure pre-stress introduction. Design parameters such as material performance, membrane thickness, and pre-stress etc. are analyzed on how to affect the SAR antenna dynamic performance. The results indicate that the pre-stress of membrane is the key factor for the whole structure mode index, and the other parameters have less effect and can be ignored. Dynamics performance of the parameters is analyzed, and optimization design is discussed, and main design parameters are obtained through the dynamics model. Research results can provide reference and guidance for the engineering design of the large space membrane structure.
Design of general ground integrated test intermediate frequency receiver for satellite transmission system (in Chinese)
GAO Xiang, YAO Xiujuan, YAN Yi, FAN Yanan, WANG Chunmei
2018, 38(1): 109-117. doi: 10.11728/cjss2018.01.109
In order to meet the task requirement of the integrated ground test for the satellite transmission system, the ground integrated test IF (Intermediate Frequency) receiver with strong generality and flexibility is designed. Based on the modularized platform with PXIe bus to exchange the information and command between the receiver and the monitor, the idea of software radio frequency is adopted to realize muti-mode system in this design, and the algorithm is implemented through FPGA according to the CCSDS standard. The design proposed in the paper has been already applied to some satellite projects, and successfully implement the task of test in each phase of the mission.
Scientific Objectives and Payloads of Chang'E-4 Missionormalsize
JIA Yingzhuo, ZOU Yongliao, XUE Changbin, PING Jinsong, YAN Jun, NING Yuanming
2018, 38(1): 118-130. doi: 10.11728/cjss2018.01.118
Abstract(2161) PDF 3118KB(1123)
The Chang'E-4 lunar explorer is composed of a communication relay satellite, a lander and a rover. The latter two are the backup of Chang'E-3. It is estimated that the Chang'E-4 explorer will be launched by the end of 2018, which is scheduled to land at the South Pole Aitken (SPA) basin, and carry out in-situ detection and reconnaissance at the farside of the moon with the communication support of the relay satellite. Chang'E-4 mission has been planned to install six scientific payloads to complete the corresponding tasks. Three payloads are installed on the lander, including the Landing Camera (LCAM), the Terrain Camera (TCAM), and the Low Frequency Spectrometer (LFS); and the other three payloads are installed on the rover, including the Panoramic Camera (PCAM), the Lunar Penetrating Radar (LPR), and the Visible and Near-Infrared Imaging Spectrometer (VNIS). The LFS is newly developed for Chang'E-4 lander, and the other five payloads are inherited instruments from Chang'E-3. Besides the above six payloads, there are also three international joint collaboration payloads to be installed on Chang'E-4 explorer, which are the Lunar Lander Neutrons and Dosimetry (LND) on the lander, the Advanced Small Analyzer for Neutrals(ASAN) on the rover, and Netherlands-China Low-Frequency Explorer (NCLE) on the relay satellite. In this paper, the scientific objectives, landing area overview, payload configurations and system designs, and the task for each payload with its main technology index of Chang'E-4 mission are mainly discussed.
2018, 38(1): 131-131.
2018, 38(1): 132-132.