Current Issue

2023, Volume 43,  Issue 1

Survey and Strategy
Strategic Study for the Development of Space Physics
WANG Chi, WANG Yuming, TIAN Hui, LI Hui, NI Binbin, FU Huishan, LEI Jiuhou, XUE Xianghui, CUI Jun, YAO Zhonghua, LUO Bingxian, ZHANG Xiaoxin, ZHANG Aibing, ZHANG Jiaojiao, LI Wenya
2023, 43(1): 9-42. doi: 10.11728/cjss2023.01.yg01
Space physics is a new interdisciplinary frontier basic discipline that has developed rapidly since mankind entered the space age. It regards the heliospheric space controlled by the sun and solar wind as a system to study the interaction between the sun/solar wind and the upper atmosphere, ionosphere, magnetosphere and even interstellar media of planets/comets. Space physics is essentially an experimental science, and space physics exploration is the basis for the development of space physics. In the new century, with the increasing space infrastructure and human high-tech activities, space physics has entered a new stage of development, emphasizing the close combination of science and application. In recent years, a series of important advances have been made in space physics at home and abroad. This paper connects with the top-level strategic design of “livable Earth−Earth system science” of the Department of Geoscience of the National Natural Science Foundation of China, teases out and summarizes the development trends of various disciplines of space physics at home and abroad in the past several years, condenses the key fields of future development of space physics in China, optimizes the discipline layout, and promotes the high-quality development of various disciplines of space physics.
Discovering the Sky at the Longest Wavelength Mission−A Pathfinder for Exploring the Cosmic Dark Ages
CHEN Xuelei, YAN Jingye, XU Yidong, DENG Li, WU Fengquan, WU Lin, ZHOU Li, ZHANG Xiaofeng, ZHU Xiaocheng, YANG Zhongguang, WU Ji
2023, 43(1): 43-59. doi: 10.11728/cjss2023.01.220104001
In this paper we describe a low frequency radio astronomy mission known as the DSL project (also “Hongmeng Project” in Chinese). It is an interferometer array made up of a formation of satellites in a lunar orbit, which makes ultralong wavelength observations in the part of orbit behind the Moon. The scientific objectives include making high precision measurement of the global spectrum, probing the cosmic dawn and dark ages; realizing ultra-long wavelength sky survey with a high resolution for the first time, opening up the last unexplored electromagnetic window; monitoring the radio activity of the Sun and planets, analyzing their interactions in the interplanetary space. The mission will obtain the whole sky map in the ultralong wavelength, and provide information on the intensity, spectrum and distribution of ultralong wavelength radio sources. It has great scientific value for the exploration of the cosmic dark ages and cosmic dawn, and investigations on the interstellar medium, origin and propagation of cosmic rays, extragalactic radio galaxies and quasars, evolution of clusters and groups of galaxies, solar activities, and planetary magnetic field.
Space Physics
Generative Model-based of Flare Hierarchic Recognition and Forecast of Extreme Ultraviolet Images in Solar Active Region
GUO Dalei, ZHANG Zhen, ZHU Lingfeng, XUE Bingsen
2023, 43(1): 60-67. doi: 10.11728/cjss2023.01.220214015
In the past 20 years, massive solar images and space meteorological data that have been transmitted back continuously and constantly with increasing space-based observatories launched, provide a promising material basis for the application of artificial intelligence technology to forecast and early warning solar activities. However, due to the less the extreme solar eruption and therefore the smaller relevant sample size, a slightly more the moderate solar activities outbreak and a little more the sample data set size, and the common routine non-outbreak space-weather always occurring and thus the samples become concentrated, thereby these condition and phenomenon result in sample imbalance and unlabeled data and so on which seriously affects the wide application of machine learning methods in the field of space weather forecasting and early warning. To handle the imbalance disturbance of sample data set for flare hierarchic recognition and forecast, this paper designs artificial intelligence algorithms for extreme ultraviolet images of solar active regions. Firstly, a dataset of extreme ultraviolet images of solar active regions from SOHO and SDO from 1996 to 2015 was constructed. Then the generated models combined classification head and initialization of convolution kernel are well-designed, and better index of accuracy for M and X flare are experimentally achieved and proved. Simultaneously, in terms of lightweight networks for deep learning, some comparison and analysis of multi algorithms on Meta learning were also discussed, this proposed method achieves finally 10% and 7% increments in POD accuracy compared with ordinary deep learning based method and unsupervised metric learning method, respectively.
High Dynamic Range Solar Radio Imaging Based on Deconvolution Using Prolate Spheroidal Wave Functions
ZHANG Rongyu, YAN Jingye, WU Lin, WU Ji
2023, 43(1): 68-77. doi: 10.11728/cjss2023.01.211125126
When the synthetic aperture radio telescope is used to observe the Sun, faint sources can be revealed by accurately removing the bright extended sources. Moreover, high dynamic range imaging can be achieved. The inherent limitations of using image pixels as basis functions in the CLEAN algorithm commonly used in radio astronomy lead to poor results for modeling extended sources. In this paper, a deconvolution method based on Prolate Spheroidal Wave Functions (PSWF) is applied to solar radio imaging to overcome the limitations of the CLEAN algorithm. The optimal PSWF orthogonal basis is determined by the Region of Interest (ROI) in dirty images and UV coverage of the interferometric array. The PSWF orthogonal basis is applied to the deconvolution of the solar radio images observed by the uniform circular array to confirm its efficiency. Moreover, the performance of the CLEAN algorithm and the method using PSWF were quantitatively compared from two aspects including dynamic range and fidelity. The faint sources in the residual dirty images produced by deconvolution using PSWF orthogonal basis are closer to the true model. A higher dynamic range imaging can also be obtained by using PSWF.
Inversion Analysis of GEO Plasma Environmental Parameters Based on BP Neural Network
ZHANG Haicheng, QUAN Ronghui, ZHANG Chengyue
2023, 43(1): 78-86. doi: 10.11728/cjss2023.01.220311028
The surface charging effect induced by the space plasma environment may interfere with the operation of spacecraft, which can lead to the failure of solar cells and other components. It is shown that the high-energy plasma environmental parameters can also be obtained by taking the electrical potential curve of the dielectric surface in the GEO environment as input under the assumption of double Maxwell distribution. Firstly, the influence of GEO plasma environment parameters on the surface charging potential curve is analyzed, indicating that the high energy peak plays a decisive role in the charging process. Then, BP neural network is established by MATLAB, and the network training data is obtained according to multiple groups of charging curves calculated by COMSOL. Finally, the average relative error of plasma density and temperature inversion is 0.42% and 0.03%, and respectively, and the overall relative error is within 0.1%~5.6%. Results showed that it was feasible to use a neural network to invert the plasma environment, and the method can be used as a reference for comparison of the detection results of the space plasma environment. The inversion results can be used as the input conditions for surface potential calculation of non-detection points of spacecraft.
Effects of Solar Extreme Ultraviolet Radiation on Thermospheric Neutral Density
WANG Hongbo, ZHANG Mingjiang, XIONG Jianning
2023, 43(1): 87-100. doi: 10.11728/cjss2023.01.211217130
The Solar Extreme Ultraviolet (EUV) radiation is well known as the major source of energy of driving the Earth atmospheric motion and transformation. The 10.7 cm solar radio flux (F10.7) instead of EUV measurement is often used in the thermospheric neutral density models, to calculate the thermosphere density and temperature. In this paper, the continuous measurements of EUV from SEM instruments onboard the SOHO satellite during 2001-2021 are directly compared with the densities derived from accelerometers onboard the CHAMP, GRACE-A and SWARM-C satellites, to reveal the essential relation between the solar EUV radiation and the thermosphere density. It is found that the correlation coefficients between the EUV data and the densities are obviously greater than those between the F10.7 indexes and the densities, which proves that the solar EUV radiation is the dominant energy source of heating the thermosphere rather than the radio radiation. From the liner regression slopes at different local time, it is shown that the maximum value occurs at 15:00 LT (corresponding to 14:00-16:00 LT), while the minimum value at 01:00 LT (00:00-02:00 LT), which confirms that the EUV radiation derives the diurnal variation of the thermosphere. According to the statistical results from three satellites with different orbital altitudes, it is indicated that in the 350~500 km altitude region, the heating effect of the EUV radiation at lower altitude is more intense than that at higher altitude (considering absolute variation). Because of the high spatial resolution of the observation of three satellites, the difference in the effect of the EUV radiation at various local time and geographic latitudes can be concluded: the slope in summer hemisphere is greater than that in winter hemisphere; in the dayside, the slope at the mid-latitudes is greater than that at the equator and high latitudes; in the nightside, the maximum of the slope appears at the high latitude of summer hemisphere, which is not described by the thermosphere models such as DTM2000 and NRLMSISE00 yet. In order to improve the modeling of the effect of the EUV radiation, the fitting method of six-order spherical harmonics is proposed. Compared with the formulas of the present models, the spherical harmonics are more valuable in improving the model construction or correction of the EUV effect and the thermosphere diurnal variation. At last, the physical mechanism of statistical results is discussed by considering the energy transmission and meridional circulation in the thermosphere.
Simulation on the Impact of the Sudden Process of Solar Activity on the Near Space Atmosphere
LIU Dan, YANG Junfeng, HU Xiong, XIAO Cunying, CHENG Xuan
2023, 43(1): 101-111. doi: 10.11728/cjss2023.01.210929104
Space weather has important effects on the Earth and near-Earth space, while large space weather events have different effects on the dynamics and composition of the pelagic atmosphere. The Whole Atmosphere Community Climate Model (WACCM) is used to simulate the effects of three types of events on atmospheric parameters of high altitude atmospheric parameters in the near space, atmospheric temperature, density and ozone through F10.7, ion production rate, Kp, and Ap index settings, respectively, for solar flares, solar protons and geomagnetic storms. The results show that flare events have the most significant effect on the temperature and density of the near space atmosphere among the three types of events, and the increase in stratospheric atmospheric temperature is caused by the photochemical reaction caused by stratospheric ozone absorption of ultraviolet radiation caused by the enhancement of radiation during the solar flare event, the increase of temperature in stratosphere and low thermosphere is roughly 2~3 K, and the relative density of the lower thermosphere increases within 6%. Solar proton events and geomagnetic storm events mainly affect the low thermosphere, but solar proton events and magnetic storm events disturb the temperature of the lower thermosphere by no more than 1 K.
Space Astronomy
An Intelligent Detection Method of Astronomical Transients Based on Lightweight CNN Model
LI Xiaobin, XUE Changbin, DAI Yuqi, ZHOU Li
2023, 43(1): 112-118. doi: 10.11728/cjss2023.01.211224133
Astronomical Transients carry rich information about the nature and evolution of celestial bodies, and their detection and research have extremely important scientific value. Most of the radiation peaks of astronomical transients are in X-rays or Gamma rays. The observation advantages of space-based telescopes in these high-energy bands are unmatched by ground-based telescopes, and they are more suitable for transients observation, but due to the constraints of the performance of on-board computers, it is difficult to implement complex detection algorithms that rely on the powerful ground computing power. In response to the above problems, a transient detection algorithm is proposed based on the lightweight Convolutional Neural Network (CNN) model, and the model deployment is implemented on the embedded ARM platform. The experimental results show that the model complexity and computational complexity of the lightweight CNN transients detection algorithm proposed are less than 1/4 of the Deep Hits algorithm, while the accuracy rate can reach 96.52%, and it can be applied to a space-borne limited computing power platform to realize real-time detection of space-based transients in the future.
Dim Small Object Detection Method Based on Statistical Feature Space Extraction and SVM
WANG Cunyuan, ZHENG Wei, LI Mingtao
2023, 43(1): 119-128. doi: 10.11728/cjss2023.01.211231136
Small object detection is the premise of small object defense and early warning. Aiming at the problems of low signal-to-noise ratio and difficult detection of small object targets, a very dark and weak small object detection method based on statistical feature space extraction and SVM is proposed. It is different from traditional methods to detect targets based on the instantaneous energy difference or the accumulation of instantaneous energy difference between target energy and background noise energy in time or space. This method does not directly depend on the target energy, but extracts the disturbance to the stability when the moving target passes through the background to retrieve the moving target. The input image sequence is transformed into a single pixel timing signal, the timing window is divided, the statistical features are extracted, the statistical feature space is formed by correlation, and the target change is detected by using the change characteristics of higher dimensions. The method is implemented by Support Vector Machine (SVM) transforms the dim small object detection problem into the binary classification problem of target and background, so that the method avoids the thorny threshold segmentation problem and has better generalization performance. Through the comparative analysis between real data and other classical methods, the classification accuracy is increased by 4.02%. This method can adapt to lower signal-to-noise ratio and still perform well at very low signal-to-noise ratio Stable detection performance.
Planetary Science
Data Compression Algorithm of the Ion and Neutral Particle Analyzer for the First Chinese Mars Mission
ZHENG Xiangzhi, ZHANG Aibing, KONG Linggao, WIESER Martin, KALLA Leif, QIU Tongsheng, WANG Wenjing, TIAN Zheng
2023, 43(1): 129-136. doi: 10.11728/cjss2023.01.210409047

An integrated ion and neutral particle analyzer is built for the first Chinese Mars exploration project, which has ten detecting modes. Most detecting modes of the analyzer produce data far more than data capability of the Mars project. A special data-processing method is presented, including data merging, logarithmic compression and lossless compression. By setting symbols in FPGA, all the three compression algorithms can be used serially, or only requisite algorithms are selected, making data-processing flexible. The compression ratio of data merging is 2 or 4, and logarithmic compression is 2. The compression ratio of lossless compression is necessarily related to data characteristic in different detecting mode. Furthermore, the experiment results show that the data-processing method has good performances and the data rate fulfills the requirements for the project.

Miniature Micro-focal X-ray Closed Tube and Electron Emission Difference of Cathode Wire
LI Fan, CAO Yang, MOU Huan, LIU Yaning, LI Haitao, LI Baoquan
2023, 43(1): 137-143. doi: 10.11728/cjss2023.01.211124122
In-situ measurement of planetary rock composition is the basic requirement of planetary exploration, and X-ray fluorescence analysis is an important technical means to carry out elemental composition measurement. In order to meet the needs of X-ray fluorescence analyzer for deep space detection, a miniature X-ray closed tube with micro-focal spot is designed and developed. It size is Φ15 mm×22 mm, and the focal spot size is 230 μm. The anode is grounded in operation, and the cathode is connected to the floating negative high voltage with the maximum voltage of –50 kV. In this paper, the differences of electron emission of common hot cathodes such as spiral tungsten, linear tungsten and linear rhenium tungsten hot cathodes, are studied in detail, and the electron emission efficiency of each hot cathode is measured. The test results show that the maximum electron emission efficiency of linear rhenium tungsten wire is 27.87 μA·W–1 at 200 V anode voltage, which is 4 times that of spiral tungsten wire and 9 times that of linear tungsten wire. In addition, rhenium tungsten wire has the characteristics of fast electron emission, low preheating requirement and low vacuum requirement, so it is an ideal choice for X-ray closed tube cathode wire for deep space exploration.
Research on a Low Energy Tele-focus Electron Gun
WU Wei, LIU Chao, ZHANG Xianguo, ZHANG Aibing, SUN Yueqiang
2023, 43(1): 144-155. doi: 10.11728/cjss2023.01.220208013
A low energy tele-focus electron gun is designed based on a subsystem of movable non-contact lunar surface potential detector. The electron gun consists of a diode extraction source and two three-element electrostatic lenses. The source produces a divergent beam which is then accelerated to energy Ke by lenses, and is focused into the shape of interest. By optimizing the geometric parameters of electron gun and the voltage applied to electrode, the electron beam has good optical characteristics and the electron energy is adjustable from 5 eV to 500 eV continuously. The initial radius r equals to 5 mm, and the distance p from the output electrode to the beam waist equals to 133 mm when the beam energy is 5 eV. As the beam energy increases to 500 eV, initial radius r decreases to 3 mm, and the distance p decreases to 105 mm. The electron beam reflected by lunar electric field is received by the collector plate. When working length H is between 400 mm and 600 mm, the electrons received by plate account for more than 96% of the beam electrons. The mass of the electron gun is only 408 g, which can meet the requirements of electron guns for lunar exploration.
Space Exploration Technology
Research on the Down-rate Filtering Method for Observations of Precision Ranging System of Gravity Satellite
LIU Xuan, YANG Shanshan, ZANG Rongchun
2023, 43(1): 156-163. doi: 10.11728/cjss2023.01.220321030
In the field of satellite time-frequency transfer and vector measurement technology, high-precision filtering of observations is very important. The basic requirement is to reduce noise interference while retaining effective observation information, and to achieve efficient and high-precision transmission of original information. In the development of high-precision ranging system for China’s earth gravity satellite, based on optimization of the FIR filter structure and improvement of the window function, a rate-down filtering algorithm for 10Hz raw ranging data is proposed in order to achieve high-frequency noise suppression and retain low-frequency gravity field information. CEDF for short, this algorithm has the operation efficiency of convolution, extraction and difference. Compared with other similar algorithms, the proposed method has the functions of both deceleration filtering and difference calculation, the noise suppression suppression degree is better than 44%, and the frequency cutoff characteristic is steep, and the suppression degree of the first side lobe reaches –94 dB. The algorithm not only improves the ranging accuracy and fully retains the information of gravity field, but also simplifies the post-processing process of ground data, and provides an optimal scheme for the data processing of microwave measurement system and laser measurement system. CEDF algorithm plays an important role in the engineering development of Earth gravity detection satellites in China and provides an effective means for the efficiency evaluation of loads.
Multivariate Engineering Parameter Anomaly Detection of the Satellite Based on Similarity Metric of the Symbolic Representation
SONG Huating, LIU Yurong
2023, 43(1): 164-173. doi: 10.11728/cjss2023.01.220112004
The complexity of the satellite system is increasing, and the comprehensive analysis of the abnormal correlation between the satellite with multiple parameters is important for the safe operation of the satellite and the correct execution of space tasks. Aiming at the characteristics of large amount of engineering parameter data, high parameter correlation and pseudo-period, a satellite multivariate engineering parameter anomaly detection method based on symbolized representation similarity measurement is proposed. Using real satellite engineering parameter data, based on Symbol Aggregation Algorithm (SAX), this paper studies the anomaly detection problem of satellite multiple engineering parameters, solves the problem of the context information, realizes effective fusion, and forms an optimized anomaly detection algorithm based on similarity measurement Fast-DTW algorithm. Results show that during the abnormality detection process, the recall, precision and F1 score are 0.947, 0.9 and 0.923 respectively in the real satellite power subsystem, and the algorithm can be actually used in satellite anomaly detection to improve the safety of satellite in-orbit operation.
Design and Implement of High-speed Receiving Cache System of the Satellite
SONG Jingxing, ZHU Yan, RAO Jianing, AN Junshe
2023, 43(1): 174-182. doi: 10.11728/cjss2023.01.220112005
Recently with the development of space technology, the explosive growth of remote sensing satellite image data and the demand for multi-mode operation of a remote sensing satellite camera, have produced the differential processing of different data. At the same time, it also has brought great challenges for inter-satellite data processing. The purpose of this research is to solve the problems of inter-satellite data processing, such as gigabits per second high-speed data transceiver, datas storage, file cache and so on. This study investigates the development of remote sensing satellite data processing, analyzes the transmission principle of SerDes, and formulates the operation strategy of documented class of high-speed cache. Based on hardware design and software development, the project of high-speed space-borne data processing unit with 3.2 bit·s–1 level and 64 data documents is completed. The test results show that based on SSLLP (Satellite Serial Link Layer Protocol), the high-speed serial data reception is correct and the cache strategy is effective. Most important of all, the system is efficient and reliable. This design has been applied to some on-orbit model missions, providing a reference to the design of high-speed receiving cache system of the satellite.
Electromagnetic Interference Suppression Technology for Switching Converters of Onboard Secondary Power Supply
ZHOU Li, MA Xiaoyong, WU Lin, YAN Jingye, AN Junshe
2023, 43(1): 183-189. doi: 10.11728/cjss2023.01.210922100
Electromagnetic Interference (EMI) suppression technology is an important technology to ensure that all spacecraft functional units can work normally together. The EMI in spacecraft comes mostly from the switching converters, DC/DC and the point-of-load POL. Ground tests for the EMI characteristics of the onboard switching converters are conducted. Based on the test results, an electromagnetic interference suppression design for the onboard power supply system is proposed, in which the hardware consists a highly stable crystal oscillator, a controller, a clock programmable buffer and some clock drivers, to provide a highly stable external synchronization clock for the switching converters. Meanwhile, the software design to realize a stable clock and power-on sequence control are introduced. All DC/DC and POL are working in the synchronization mode, in which the switching clocks are from external clock drivers. Finally, the feasibility and effectiveness of the EMI suppression design is verified by the method of measuring the output voltage spectrum.
Effects of Sea Surface Temperature on the CFOSAT Scatterometer Measurements
ZHAO Xiaokang, LIN Wenming, WANG Zhixiong, HE Yijun
2023, 43(1): 190-198. doi: 10.11728/cjss2023.01.220216017
Satellite scatterometer is designed to retrieve global sea surface winds by measuring the sea surface roughness. For Ku-band scatterometers, the sea surface roughness is not only affected by winds, but also by certain secondary effect, namely Sea Surface Temperature (SST). This paper presents a quantitative analysis of the SST effects on the China-France Oceanography Satellite (CFOSAT) scatterometer (CSCAT) backscatter measurements and wind retrievals. The results show that the backscatter coefficients measured by CSCAT vertically and horizontally polarized beams are both effected by SST, while for vertically polarized beams, the SST effect is nearly negligible at moderate and low incidence angles (θ < 36°). Consequently, the wind speed bias of CSCAT also changes along with SST, e.g., large SST-induced bias is associated with high incidence angles and/or low wind speed conditions. Finally, an SST-dependence Geophysical Model Function (GMF) is proposed, which opens a door for further improving the quality of CFOSAT scatterometer wind products.