2018 Vol. 38, No. 2

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2018, 38(2): 133-133.
2018, 38(2): 133-133.
2018, 38(2): 133-133.
2018, 38(2): 134-134.
2018, 38(2): 134-134.
2018, 38(2): 135-135.
2018, 38(2): 135-135.
2018, 38(2): 135-135.
2018, 38(2): 136-136.
2018, 38(2): 137-137.
2018, 38(2): 138-138.
Characteristics and Managements of Space Science Missionsormalsize
2018, 38(2): 139-146. doi: 10.11728/cjss2018.02.139
Abstract(1194) PDF 672KB(921)
There are more than ten thousands spacecrafts have been launched since 1957. About 10 percent among them are space science missions. In recent years, more funds are available for space science in China due to the fast development of the economy and innovation requirements from the government to build up a new scientific and technology power by 2050. As a result, China has launched four space science satellites since 2015, i.e. DAMPE, Shijian-10, QUESS and Insight-HXMT. Moreover, TG-2 space lab is also operating successfully. A series of important scientific outputs have been published since last year. In this paper, the management experiences of the space science missions are summarized. The special characteristics of space science missions which are different from other kind of space missions are analyzed. The understanding of these characteristics is helpful for maximizing the scientific outputs which are key for the sustainable development of space science.
Ion-scale Structures in Flux Ropes Observed by MMS at the Magnetopause
2018, 38(2): 147-168. doi: 10.11728/cjss2018.02.147
Abstract(1034) PDF 3653KB(3528)
In this paper the structures with scale of ion inertial length (di) in flux ropes at the magnetopause are studied based on MMS measurements. The results show that currents ( j m) of di scale are found to exist in many flux ropes with different scales, which flow in the -M direction in magnetopause local coordinates (i.e., in the same direction of the Chapman-Ferraro current at the magnetopause) and are carried by electrons' motion in the +M direction ( v em). Within the current structures, magnetosheath and magnetospheric plasma populations are mixed; the magnetic field has open topology; ions are non-magnetized, while electrons are frozen-in with the magnetic field lines; the N-component of electric field ( E n), which is Hall electric field in nature, substantially enhances (up to about 20mV·m-1), accompanying with notable fluctuations. Detailed analysis shows that the current, separation of electrons' motion from ions and the Hall electric field are closely related to each other, and obey the general Ohm's Law. In addition, we have also analyzed the MMS measurements of magnetic reconnection events at the magnetopause. It is found that structures similar to those in flux ropes are also present inside the reconnection region in many cases. Their scales are of di length. The directions (magnitudes) of the Hall electric field E N, current filament j M and electron velocity v eM are as same as (close to) those in flux ropes. On the bases of above observations and making use of the classical flux rope models, how the di-scale structures in flux ropes are formed is studied. It is suggested that they are likely to originate from the corresponding structures in the reconnection region at the magnetopause which play an essential role in the formation process of di-scale flux ropes.
Kinetic Magnetic Turbulence Associated with Flux Transfer Events Observed by THEMIS Satellite ormalsize
ZHOU Zhaodi, ZHANG Hui, NI Binbin, ZHANG Xiaojia, ZHU Changbo, FU Song
2018, 38(2): 169-177. doi: 10.11728/cjss2018.02.169
Intense magnetic fluctuations are recorded in the magnetosphere near the magnetopause when Flux Transfer Events (FTE) are passed by the THEMIS satellites. The power spectra of these fluctuations obtained by Fast Fourier Transform (FFT) show that the Power Spectra Density (PSD) peaks around the disturbance frequency of FTE (about 0.1Hz), and decreases from the proton gyrofrequency (about 1Hz) to 64Hz following a power law of P0f-α. These fluctuations are interpreted as magnetic turbulences in the kinetic regime in the Low Latitude Boundary Layer (LLBL). The results show that both the PSD and the slopes of the power spectra α decrease when the observing satellite position is more and more away from the magnetopause or the FTE location in the LLBL. However, α and the PSD are independent from the azimuthal position of FTE or local time of the low latitude magnetopause. All these observations suggest that the moving FTEs are the source for these magnetic fluctuations. Large scale perturbations on the magnetopause, e.g. FTEs and the associated magnetic turbulences, provide a hint which may reveal the interaction between the magnetosheath and the magnetosphere in a kinetic scale. Whether the magnetic turbulences can provide enough viscosity for the forming of the flow vortices on the magnetospheric side of FTEs or not need to be further confirmed.
Comparison of Short-time Prediction of f0F2 Using Kalman Filter and Autocorrelation Methodormalsize
ZHOU Yi, ZHANG Yuannong, JIANG Chunhua, ZHAO Zhengyu, LIU Jing
2018, 38(2): 178-187. doi: 10.11728/cjss2018.02.178
f0F2 forecast is a significant research aspect in ionospheric study, and much work has been done to improve its prediction performance. In this paper, f0F2 data from four ionospheric observation stations (Beijing, Changchun, Qingdao and Suzhou) in 2011 are used to predict f0F2 one hour in advance with the method of Kalman filter and autocorrelation analysis. Furthermore, comparisons are carried out between ionosonde observation, the values predicted by International Ionospheric Reference Model (IRI), and the estimated values of Kalman filter and autocorrelation method. The results are described as follows. For the method of Kalman filter, its Root Mean Square Error (RMSE) and Relative Error (RE) are 0.532MHz and 8.11% respectively. The RMSE and RE values are reduced by 1.035MHz and 14.58% compared with the corresponding values obtained by IRI. In terms of autocorrelation analysis, its RMSE and RE are 0.967MHz and 11.46%, and are reduced by 1.035MHz and 11.23% compared with the corresponding values obtained by IRI. It can be concluded that the prediction precisions of above-mentioned two methods have a great promotion compared with the IRI results. Moreover, further comparisons of these three methods are carried out during a geomagnetic storm. Experimental results indicate that Kalman filter method is better than autocorrelation analysis method and IRI model, which might provide suggestions for choosing a method for short-term prediction of f0F2.
Numerical Simulation of Typhoon-generated Gravity Waves Observed by Satellite and its Direct Validationormalsize
YAO Zhigang, HONG Jun, HAN Zhigang, ZHAO Zengliang
2018, 38(2): 188-200. doi: 10.11728/cjss2018.02.188
To analyze the stratospheric gravity waves induced by strong convection, Typhoon Soulik is investigated by the mesoscale model WRF-ARW (3.5 Version), ECMWF and AIRS observations. The WRF model results show that strong stratospheric gravity waves are induced by Typhoon Soulik, and the background wind plays a great role in modulation of the gravity waves propagation. The wave spectrum analysis reveals that the horizontal wavelength is about 500km, the period is about 3~5h, and the vertical wavelengths are gradually stretched with height about 10~14km, 14~18km and 22~26km in the height of 20km, 30km and 40km. The momentum flux and wave drag are also analyzed. At last, the direct comparison of WRF, ECMWF and AIRS observations based on a radiative transfer model indicates that the stratospheric semicircular arc wave pattern, position and horizontal scale agree well. But there are also some differences among these data. The AIRS can detect more details than WRF and ECMWF data. The order of wave intensity is AIRS, WRF and ECMWF.
Analysis and Verification of Thermospheric Density Derived from CHAMP and GRACE-A/B Accelerometer Data ormalsize
MIAO Juan, REN Tingling, GONG Jiancun, LIU Siqing, LI Zhitao
2018, 38(2): 201-210. doi: 10.11728/cjss2018.02.201
The data of thermospheric total mass density derived from the high-accuracy accelero-meter on board the CHAMP and GRACE-A/B satellites during 2001-2008 at 400km altitude are analyzed. NRLMSISE-00 is selected as the reference model for comparing with those derived density. Mean Absolute Error (MAE) and Mean Relative Error (MRE) between derived and NLRMSISE-00 model values are given. The characteristics and causes of these errors are analyzed. The density variation and their rationality are also discussed. Moreover, the reliability of the derived density is verified by TLEs density. The main conclusions are as follows. Density obtained by CHAMP is larger than those obtained by GRACE-A/B at 400km altitude. The errors between the density obtained by CHAMP and model value are smaller than those between GRACE-A/B and model. There is a global deviation between the density obtained by CHAMP and model. The density variation in the similar space environment and the density obtained by TLEs show that the density in 2001 obtained by CHAMP is lower than actual values. Examples of the density obtained by CHAMP and GRACE-A/B indicate that there are some individual characteristics of the density obtained by the satellites, and they should be analyzed and chosen in application.
Application of Time Series Method in Forecasting Near-space Atmospheric Windormalsize
LIU Tao, XIAO Cunying, HU Xiong, TU Cui, YANG Junfeng, XU Qingchen
2018, 38(2): 211-220. doi: 10.11728/cjss2018.02.211
Due to many factors, near-space environment is complex and variable. Atmospheric environmental elements are hard to be forecasted. In this paper time series method is applied to the near-space wind forecasting. Autoregressive Moving Average (ARMA) model is adopted. The zonal wind data at 88km altitude of Langfang (39.4°N, 116.7°W) MF radar form September 24 to October 24, 2015 is used for the forecasting test. In this test the data of past 7 days was used to forecast the data of the 8th day. Results suggest that ARMA model has certain applicability in forecasting the near-space atmospheric wind. The forecast effect is better when the winds have stronger regularity of change, i.e., when the sample data show a significant 24-hour cycle, the forecast effect is better, and is worse when the winds have a mutation. Compared with the observed data, results show that the forecast error of ARMA model is 9~27m·s-1, and the forecast result of ARMA model is better than that of AR model with the same order, and is slightly better than that of higher-order AR model.
Experimental study on bubble behaviors in microgravity pool boiling
LIU Peng, WU Ke, DU Wangfang, ZHAO Jianfu, LI Huixiong, LI Kai
2018, 38(2): 221-226. doi: 10.11728/cjss2018.02.221
Abstract(1138) PDF 879KB(728)
In this paper, the image analysis method is used to study the experimental data of the single bubble subcooled boiling experiment aboard the Chinese recoverable satellite SJ-10. The growth process of single vapor bubble in microgravity is extracted and analyzed. The bubble formation by the pulse excitation, steady growth of the bubble adhering to the excitation point, and its sliding over the heating surface are observed. Among the above three stages, the stage of steady growth of the bubble adhering to the excitation point can be divided into two sub-stages, i.e. expansion and retreat of the bubble base. During the bubble base expansion sub-stage, its radius can be expressed as an exponential function of time. The exponent decreases from 0.42 for the smaller size to 0.28 for the medium one, and finally to 0. The bubble size slightly retraces at the beginning of the bubble base retreat, and then slowly increases again until the subcooled liquid penetrated the bottom of the bubble completely, causing the bubble to detach from the heating surface and then slid on the heating surface under the external disturbance. The results can be used as the basis for the analysis of bubble thermal dynamics in boiling phenomena.
Experimental Study of Buoyancy Effect on Transitional Jet Diffusion Flames ormalsize
LI Dan, WANG Shuangfeng
2018, 38(2): 227-233. doi: 10.11728/cjss2018.02.227
The transition to turbulence of coflow propane-fueled jet diffusion flames was investigated experimentally with varying air coflow velocities, and the buoyancy-suppressing effect of coflow was analyzed to reveal the buoyancy effect on the transition and stability of diffusion flames. Compared to jet flames in quiescent air, a coflow with relatively high velocity can suppress the influence of buoyancy on transitional flames, and make the critical nozzle Reynolds number of transition to turbulent flame increasing, i.e., the transition process is delayed by coflow. When the coflow velocity is small, however, the critical Reynolds number stays almost the same. In the transitional regime, diffusion flames are characterized by periodic oscillation, and the oscillation amplitude decreases with increasing coflow velocity. As coflow velocity increases further, the periodicity of flame oscillation disappears eventually, and presents a randomness. Additionally, the experiments show that a larger jet nozzle results in a greater critical Reynolds number of flame transition. Such an observation is explained in terms of the local fuel jet properties taking into account of the influence of diffusion flame.
Growth of ZnTe Crystal in Microgravity on Tiangong-2 Spaceshipormalsize
LU Ye, WANG Reng, DU Yunchen, JIAO Cuiling, LI Xiangyang
2018, 38(2): 234-238. doi: 10.11728/cjss2018.02.234
Abstract(1279) PDF 881KB(1017)
Zinc telluride crystal was grown by Te-solvent method in microgravity on Tiangong-2 spaceship in 2016. The growth temperature is 800℃, and the growth rate is 0.5mm·h-1. A ground-truth experiment was performed following the space experiment, and a comparison between the two samples was studied. An orange ZnTe crystal (its size is about 10mm×6mm×2mm) can be found in the space sample. It is shown that the crystal size of space sample is larger than that of the ground sample. Because of the capillary phenomenon in microgravity, Te and ZnTe film were grown at the surface of the silicon rod of the space sample. However, a little bit of gaseous product was found at the ground sample. This result underlines the importance of microgravity for crystal growth of Group Ⅱ~VI semiconductor material. It gives the positive guidance on the growth of infrared semiconductor materials on ground such as HgCdTe, CdZnTe and ZnTe.
Geocentric Position Extraction Algorithm for Earth Sensor Image of Lunar Roverormalsize
PU Junyu, ZHENG Yong, CHEN Shaojie, LI Chonghui, WANG Dingwei, HE Donghan
2018, 38(2): 239-248. doi: 10.11728/cjss2018.02.239
The Earth is the largest visible celestial body on the moon, whose range of motion on the celestial sphere is small. Moreover, it has no phenomenon of rise and set. When lunar rover is exploring on the moon surface facing toward the Earth, the Earth sensor can be used to photograph the Earth, thus achieving long term autonomous celestial navigation. Geocentric position extraction algorithm for Earth image is one of the key techniques of celestial navigation using Earth sensor, which directly determines the precision of the sensor.In this paper, the Earth imaging law is analyzed by studying the projection model of Earth sensor lens. An algorithm for extracting the geocentric position of the Earth sensor image free from Earth phase change is presented. Two steps are proposed to realize full screening of the real edge of the Earth, including semi search method and cyclic search method, and then geocentric position can be fitted. The semi-physical simulation experiments show that the algorithm can effectively extract geocentric positions for different phase images and it earns the external average accuracy of 9.78"~16.68". Under the circumstance of random change of experimental conditions, the maximum difference of standard deviations of external accuracy exceeds no more than 0.98".
Pseudo-range Differential Integrated Time Synchronizing Method for Anchor Nodesormalsize
OUYANG Xiaofeng, LÜ Daqian, ZENG Fangling
2018, 38(2): 249-254. doi: 10.11728/cjss2018.02.249
Traditional time synchronization method could reach a high precision for distributed nodes, but does not apply to the spatially non-contact nodes. In order to solve the above problems, a time synchronization method based on pseudorange differential GPS was proposed, and the system principle and synchronization scheme are given. Moreover, the clock model of the Anchor Nodes (ANs) is built to estimate synchronization parameter, which is solved by the Total Least Squares (TLS) method. The Kalman Filter (KF) method is derived from the theoretical time synchronization module, which can enhance the real timing and precision. The results of numerical simulating show that the proposed system synchronization and parameter estimation methods can control the synchronization accuracy of distributed node in sub-nanosecond level.
Kunpeng-1B sounding rocket nutation analysis and simulation after separation (in Chinese)
GAO Dong, CUI Feng, HAN Peng, LIU Cheng, BIAN Chunjiang
2018, 38(2): 255-260. doi: 10.11728/cjss2018.02.255
Abstract(1077) PDF 795KB(614)
Kunpeng-1B sounding rocket was launched successfully by the National Space Science Center of Chinese Academy of Sciences at Danzhou, Hainan on April 27, 2016. The attitude of the payload service system fell into nutation mode after being separated from the launching vehicle, which is beyond the designing limits. In this paper the possible factors triggering the nutation movement are analyzed, the attitude dynamics equations of the payload service system are set up, and the nutation movement is reproduced by numerical simulation. By comparing the simulating nutating results with the real flying nutation, the main elements triggering the nutation are obtained. The results can provide reference for the follow-up sounding rocket designing.
Design and Implementation of an Automatic Image Enhancement Algorithm Based on FPGAormalsize
FAN Bin, YU Qifeng
2018, 38(2): 261-270. doi: 10.11728/cjss2018.02.261
Since there are many too dark or too bright areas in pictures that shot in the space, the corresponding images are uneven distributed, and the image quality is damaged. How to improve the processing speed of the algorithm and how to implement the algorithm by the embedded system are also key problems for space application. In this paper, the automatic image enhancement algorithm which is suitable to be implemented by the FPGA is proposed to solve these problems. The basis of the proposed algorithm is the piecewise linear transformation algorithm. In practical, firstly, the K-means clustering is used to segment the histogram into several sections automatically. Secondly, the quantitative relationship between the histogram distribution and the coefficients of the piecewise linear function is established. As a result, the coefficients can be automatically calculated. Thirdly, the corresponding FPGA system is implemented. And the high-performance parallel pipelined technology is used to ensure the real-time processing ability of the system. The simulations and the experimentations show that the proposed FPGA system is characterized as real-time processing ability and good adaptability. It can achieve good processing effects for different sceneries, and can be used in various practical applications.