2018 Vol. 38, No. 6

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2018, 38(6): 839-839.
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2018, 38(6): 839-840.
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2018, 38(6): 840-840.
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2018, 38(6): 841-841.
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2018, 38(6): 841-841.
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2018, 38(6): 842-842.
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Influence of Solar Activity on Ionospheric TEC Change
LI Yongtao, LI Jianwen, DAI Taogao, PANG Peng
2018, 38(6): 847-854. doi: 10.11728/cjss2018.06.847
Abstract(866) PDF 4571KB(467)
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In order to study the effect of solar activity on ionospheric TEC variation, the correlation between solar sunspot number, daily average solar flux F10.7 index and ionospheric TEC from 2000 to 2016 and the correlation between solar activity and ionospheric TEC changes 15 days before and after the X9.3 extra large flare on September 6, 2017 are analyzed. The results are as follows. In terms of the data of 17 years from 2000 to 2016, there is a strong overall correlation between solar sunspot number, solar F10.7 index and TEC with a big local difference. That is, local correlation is uneven. There is a strong positive correlation between solar sunspot number, solar F10.7 index and TEC before and after this flare burst. The effect of solar activity on TEC is delayed about 2 days. The influence of solar activity on global ionospheric TEC is not synchronized. There is about 1 day delay from high latitude to low latitude, and its influence on low latitudes is far greater than that of middle and high latitudes. In general, solar activity is the main reason for the change of ionospheric TEC, but other important factors may exist locally.
Statistical Analysis of the Ionosphere Disturbance Based on the IGS Global Ionosphere TEC Map
HOU Weizhen, ZHANG Shaocheng, YIN Fei, YU Tao
2018, 38(6): 855-861. doi: 10.11728/cjss2018.06.855
Abstract(723) PDF 1867KB(839)
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The ionospheric Total Electron Content (TEC) is an important parameter for space weather research and helps to understand the changes of space environment. In this paper, 18 years' IGS ionospheric TEC grid data from 1999 to 2016 are employed to calculate the ionosphere disturbance over four different areas, including high, middle, mid-low and low magnetic latitude. The thresholds of the ionosphere disturbance are selected according to the statistic results on different TEC grid point, and the relationship between ionosphere disturbance and other physical elements, such as solar activity, geomagnetic latitudes and geomagnetic activities, are studied. The results show that the ionosphere disturbances are closely related with the solar activities. The occurrence rate of TEC disturbance event's is about 1.79% at lower solar activity, while the rate increases to 10.18% at higher solar activity. The high latitude areas always have higher ionosphere disturbance rate than other areas. The correlation coefficient between TEC disturbance index of middle and mid-low magnetic latitude and geomagnetic index Ap are 0.57 and 0.56 respectively. The coefficients in high and low magnetic latitude are 0.44 and 0.39 respectively. There are different correlations between ionosphere disturbance of different areas and global geomagnetic index Ap, and using regional geomagnetic index could help improving the correlations between geomagnetic index and ionospheric disturbance.
Analysis of the Ionospheric Irregularity Events in the Low Latitude of East Asia Based on Multiple Instruments
SHANG Sheping, SHI Jiankui, WANG Zheng, WANG Guojun, CHENG Zhengwei, WANG Xiao
2018, 38(6): 862-870. doi: 10.11728/cjss2018.06.862
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The ionospheric irregularity events observed on November 20, 2011 were analyzed using ground- and space-based instruments at Hainan station (19.5°N, 109.1°E, dip: 13.6°N) and magnetic equatorial region. The comprehensive observations of Hainan station VHF radar, ionospheric scintillation and digisonde show that strong ionospheric irregularities occurred near the sunset, and the irregularities pattern mainly appeared as radar plume and strong scintillation. Combined with the observations obtained by magnetic equatorial GPS and the C/NOFS satellite, the radar plume and strong scintillation over Hainan region near the sunset are obviously related to the primary plasma bubble generated in the magnetic equatorial region of the South China Sea.
Critical Value of Initial Disturbance Wave-number Affecting Rayleigh-Taylor Instability in Equatorial and Low-latitude Ionosphere
SUN Zhiqiang, FANG Hanxian, WANG Sicheng, MA Jie
2018, 38(6): 871-878. doi: 10.11728/cjss2018.06.871
Abstract(550) PDF 2448KB(419)
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The sufficient condition of Rayleigh-Taylor instability in equatorial ionosphere has been derived by Ref.[1]. In this paper, the sufficient condition is expanded to low-latitude areas of ±30° magnetic latitude. To study how the initial disturbance wave-number affects the generation of plasma bubble, the variations of λmin as initial disturbance wave-number are analysed. According to the dichotomy method, the critical wave-number αc is attained for λmin=1. Moreover, the characteristics of αc with geomagnetic latitudes, longitudes, seasons, solar activities, local times and the horizontal eastern electric filed are analyzed. The main conclusions are as follows. The variations of αc with latitudes, longitudes, seasons, solar activities, and local times are consistent with plasma bubbles and scintillations. The shorter the wave-length is, the easier it would be to generate the Plasma Bubbles (PB). The enhancements of the horizontal eastward electric filed are helpful to initiate PBs. The value of αc is benificial to decide the best disturbed way in the ionospheric artificial modification.
Influence of Ionospheric Sporadic E on Radio Propagation in HF and VHF Band
ZHANG Yabin, WU Jian, XU Zhengwen, XU Bin, XUE Kun, ZHAO Haisheng, WANG Xiaobin
2018, 38(6): 879-885. doi: 10.11728/cjss2018.06.879
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The Es layer is a sporadic E layer in the ionosphere, and its electron density can reach 100 times more than normal E layer. The Es layer can reflect radio waves in VHF (30~150MHz) band, and it has a significant impact on radio wave propagation in high HF (10~30MHz) band. In this paper, the observation data of the vertical and oblique ionospheric sounders is used to study the propagation characteristics of HF band radio waves in the Es layer. The attenuation coefficients of different types and altitudes of Es layer are obtained. According to the daily variation of f0Es, the diurnal variation of attenuation coefficient in HF band is obtained, and then the influence of Es layer on shortwave propagation is analyzed. In the absence of the ionospheric Es layer, it is not possible to achieve long-range VHF communication by the ionosphere. In order to quantitatively analyze the propagation attenuation of the VHF link by the Es layer, the ionospheric Es layer attenuation model is constructed by fitting the observation data of the European Broadcasting Union (EBU) links. The model and ITU (International Telecommunication Union) model are compared with the observed data. The results show that the model established in this paper is more accurate than ITU model.
Observations of the Prominent Sporadic Sodium Layer over Haikou
YANG Dali, ZHANG Tiemin, WANG Jihong, YAN Chunxiao, PENG Hongyan
2018, 38(6): 886-890. doi: 10.11728/cjss2018.06.886
Abstract(801) PDF 899KB(374)
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The prominent Sporadic Sodium Layer (SSL) were observed by the lidar over Haikou (20°N, 110°E) at 02:47LT on Nov. 2, 2011. The peak density of SSL was 37087cm-3, and its Full Width at Half Maximum (FWHM) was 0.9km. The characters of the peak density and altitude before and after the SSL occurrence were analyzed. 222 SSL events were detected in 377 observation days from 2010 to 2013. The SSL occurrence rate is 12.4h at our location, but only one SSL which peak density was beyond 30000cm-3. By comparing the corresponding data of the nearest ionosonde and VHF radar at Danzhou (19.5°N, 109.1°E), it was found that SSL is closely related to Es. Among the 8 pairs of SSL and Es events checked, all peaks of SSL were accompanied by the lowest Es within 5km in altitude, and 6 pairs of them were correlated within ±0.5h in time. A Nd:YAG laser and pumped dye laser were used to generate the probing beam. The wavelength of the dye laser was set to 589nm by a sodium fluorescence cell. The energy and divergence of the beam were 45mJ and 1mrad, respectively. The backscattered fluorescence photons from the sodium layer were collected by a telescope with a 1000mm diameter primary mirror.
Advances on Molecular and Biological Effects of Mammalian Cells in Microgravity Environment
YU Yang, WANG Shengwei, XU Zhaoxian, JIN Mingjie, YANG Shulin
2018, 38(6): 891-899. doi: 10.11728/cjss2018.06.891
Abstract(725) PDF 990KB(440)
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With the continuous development of manned space program, astronaut health problems, such as cardiovascular diseases, immuno-suppression, muscle wasting, and osteoporosis, etc., caused by microgravity have attracted extensive concern, and these astronaut-derived health problems have become a major obstacle to the exploration of space. Many studies have focused on the changes of body and cell in microgravity conditions. Recent studies have shown that cell degradation and changes in the cytoskeleton can be induced by microgravity, and a series of changes caused by microgravity at molecular level were also found. In this paper, the recent studies on the behavior of immune cells, endothelial cells, bone cells and cancer cells in microgravity condition are reviewed. The results can provide instruction and reference for the further study of the disease occurrence in microgravity conditions, and provide some ideas for the treatment of diseases caused by microgravity conditions.
Effects of Laser and Hot Wire Modes on Ignition and Combustion of Single Multicomponent Droplet
CUI Yanling, WANG Baorui, YUAN Hongliang, KONG Wenjun
2018, 38(6): 900-908. doi: 10.11728/cjss2018.06.900
Abstract(712) PDF 2127KB(349)
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The ignition and combustion characteristics of multicomponent fuel as single suspended droplet are conducted. The effects of laser and hot wire ignition on droplet burning rate, flame morphology and ignition delay time are analyzed. The experimental results show that, as the hot wire ignition time increases, the burning rate increases with the increase of natural convection around the droplet. Under ambient environment, the droplet flame is a teardrop shaped flame, and the maximum ratio between the flame height and the initial droplet diameter is about 18. When t/tb>0.4, the flame height of the droplet when heated by the hot wire is 5D0 higher than that in subsequent non-heating stage, and 5~10D0 higher than that of the droplet ignited by the laser. Compared with the hot wire ignition, the laser ignition responses faster and causes less interference to the flow field near the droplet. Therefore, the laser ignition is an ideal method of the droplet combustion experiments on the ground. With a fixed laser pulse time, the ignition delay time of single droplet becomes shorter when the laser intensity increases.
Simulations of the Spacecraft Charging and Wake Effects in the Solar Wind
BI Jiayi, LI Lei
2018, 38(6): 909-914. doi: 10.11728/cjss2018.06.909
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Surface charging and wake effects can disturb the plasma around the spacecraft and affect the measurements of spacecraft payloads. In this paper the Spacecraft Plasma Interaction Software (SPIS) is used to simulate the interaction between the solar wind and the spacecraft, in order to reveal the ion, electron, photoelectron, and electric potential distributions around the spacecraft. The results show that, since the plasma is tenuous, the electrons collected by the spacecraft give a much smaller current than the photoemission current, and the spacecraft could be charged to positive potential. A negatively charged wake will form downstream the spacecraft. It is demonstrated that the wake features can be altered by the photoemission. The scale of the wake can be larger due to the surface photoemission. It is also concluded that, since the bulk flow kinetic energy is much larger than the spacecraft potential energy, the size of the wake depends on the dimension of spacecraft. The wake can be substantially larger behind a larger spacecraft with the same parameters in the solar wind.
Orbit Determined Method of High Elliptical Orbit Satellite Based on BDS Navigation and Inter-satellite Link
LI Lan, LI Changgeng, HUANG Wende, ZHOU Yifan
2018, 38(6): 915-924. doi: 10.11728/cjss2018.06.915
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The traditional ground tracking telemetry control and Global Navigation Satellite System (GNSS) are unable to achieve the whole orbit observation of the High Elliptical Orbit (HEO). An autonomous navigation method is put forward, which combines the satellite navigation and inter-satellite link. This method is based on the Beidou Navigation Satellite System (BDS) navigation and inter-satellite link complementary characteristics of HEO monitoring after analyzing the observation geometry and the coverage characteristics of the typical HEO track. The autonomous navigation algorithm is designed for orbit determination, which combines the satellite navigation and inter-satellite link data based on Extended Kalman Filter (EKF). The HEO satellite orbit determination is divided into some segments. The analysis results show that the proposed method can improve the HEO satellites' observation geometry for the whole orbit, and the orbit prediction precision is enhanced by over two orders of magnitude compared with the BDS navigation method. Furthermore, the occupation of the inter-satellite link resources decreases significantly.
Analytical Formation Keeping Control Strategy for Micro-satellites
WANG Youliang, ZHENG Jianhua, LI Mingtao
2018, 38(6): 925-933. doi: 10.11728/cjss2018.06.925
Abstract(736) PDF 1225KB(357)
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Formation keeping is the foundation of satellite formation flying. J2 term and atmospheric drag are the main perturbations for the low Earth orbit satellites, which can cause the long-term change of relative velocity and formation drift. Firstly, the mean relative velocity is used to denote the drift rate of satellite formation, and the analytical representation between the mean relative velocity and impulse maneuver is derived. Then the mean relative acceleration is developed, and the relative motion under the main perturbations is equivalent to a uniformly accelerated motion. Finally, it is combined with the single side limit cycle control method, and an analytical formation keeping control strategy based on the inter-satellite ranging information is designed. The numerical simulation results indicate that the strategy is simple and effective, which is easy to implement in engineering and suitable to the autonomous control for micro-satellites especially.
Influence of Covering Material Wrinkles on Space Object's Optical Scattering Characteristics
LI Peng, LI Zhi, XU Can
2018, 38(6): 934-943. doi: 10.11728/cjss2018.06.934
Abstract(511) PDF 3242KB(656)
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The irregular wrinkles of coating materials on space object's surface have a significant influence on its optical scattering characteristics. The wrinkles of space object's surface are classified and the main causes of these wrinkles are analyzed. By taking the gold polyimide film samples as the research object, a radiance measurement system is set up to obtain the radiance data of different wrinkled samples. The experimental radiance is converted into magnitude. There are great differences in the magnitude curves by comparing the theoretical calculations and experimental measurements. The single specular reflection phenomenon disappears and the reflection energy is scattered at multiple angles. Moreover, the higher degree of winkles is, the more strong scattering points are. The results show that the influence of the coating wrinkles must be taken into account when calculating the space object's optical scattering characteristics. The numerical calculation model can be revised according to the wrinkles conditions, which have great significance on the detection and identification of space objects.
Improvement and Hardware Implementation for Bit Rate Control Algorithm of JPEG-LS
CHEN Cong, ZHANG Xuequan, ZHOU Shengyu
2018, 38(6): 944-952. doi: 10.11728/cjss2018.06.944
Abstract(697) PDF 1691KB(436)
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JPEG-LS is a lossless/near-lossless image compression standard based on context modeling. Because of the simplicity and little occupation of resource, it is suitable for satellite image compression where the hardware resource is limited. However, in JPEG-LS near-lossless mode, the bit rate is difficult to control. To solve this problem, a new bit rate control algorithm based on dynamic rate table is proposed based on JPEG-LS. Test results show that the new algorithm is more efficient comparing with the existent bit rate control algorithm. The quality of reconstruction image is also better in the aspects of Peak Signal to Noise Ratio (PSNR) and Structural Similarity Index (SSI). The rate control algorithm can be implemented on Xilinx Virtex4, in which the slice occupancy rate is 21% and the synthesized clock frequency is 60MHz. It can satisfy the demand of satellite image compression.
Vector Calibration Method for Orthogonality Correction of Three-axis Magnetometers
WANG Pengfei, ZENG Li, TANG Wenqing, WANG Jing
2018, 38(6): 953-959. doi: 10.11728/cjss2018.06.953
Abstract(950) PDF 2200KB(403)
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An vector calibration method is proposed based on the error separation technique for orthogonality correction of three-axis magnetic sensor. Mathematical model of vector calibration was established for orthogonality correction. The installation error in the process of correction was calibrated by the error separation technique. Model parameters were solved with a kind of method which combined the Kalman filtering and least square method and got a matrix that can be used to the orthogonality correction. The simulation and experiment results showed that the whole calibration process was feasible and effective. The error reduced from 0.0962nT to 0.0019nT in the case of total magnetic field was 2.5nT. This method has been applied to the orthogonality correction of an satellite-boneinduction magnetometer.
Integrated Payload OBDH Technology for Deep Space Exploration
WANG Lianguo, ZHU Yan, ZHOU Changyi, AN Junshe, RAO Jianing
2018, 38(6): 960-970. doi: 10.11728/cjss2018.06.960
Abstract(623) PDF 3280KB(399)
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Deep space explorations put forward higher requirements on miniaturization and autonomy to probe's payload On-board Data Handling (OBDH) system. The novel highly integrated payload OBDH architecture is constructed by integrating payload electronics units and traditional payload OBDH units. This architecture can realize intensive use of resources, improve information unification and implement onboard autonomy conveniently. Payload OBDH architectures of the Chang'E series probes are introduced. Two novel integrated payload OBDH architectures are proposed, the low-cost scheme has been applied to China's first Mars exploration. Payload OBDH technical requirements for future deep space exploration are analyzed, and payload OBDH development trends are prospected.
2018, 38(6): 977-977.
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2018, 38(6): 978-979.
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