2020 Vol. 40, No. 4

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2020, 40(4): 439-439.
2020, 40(4): 439-439.
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Research Articles
Science Missions Using CubeSats
2020, 40(4): 443-461. doi: 10.11728/cjss2020.04.443
As the role of missions and experiments carried out in outer space becomes more and more essential in our understanding of many earthly problems, such as resource management, environmental problems, and disaster management, as well as space science questions, thanks to their lower cost and faster development process CubeSats can benefit humanity and therefore, young scientists and engineers have been motivated to research and develop new CubeSat missions. Not very long after their inception, CubeSats have evolved to become accepted platforms for scientific and commercial applications. The last couple of years showed that they are a feasible tool for conducting scientific experiments, not only in the Earth orbit but also in the interplanetary space. For many countries, a CubeSat mission could prompt the community and young teams around the world to build the national capacity to launch and operate national space missions. This paper presents an overview of the key scientific and engineering gateways opened up to the younger scientific community by the advent and adaptation of new technology into CubeSat missions. The role of cooperation and the opportunities for capacity-building and education are also explored. Thus, the present article also aims to provide useful recommendations to scientists, early-career researchers, engineers, students, and anyone who intends to explore the potential and opportunities offered by CubeSats and CubeSats-based missions.
ULF Wave in the Magnetotail Plasma Sheet Induced by Interplanetary Shock
SONG Xiaojian, ZUO Pingbing, SHEN Xiaochen
2020, 40(4): 462-470. doi: 10.11728/cjss2020.04.462
Ultra Low Frequency (ULF) waves play an important role in energy transport from the solar wind into the magnetosphere. The ULF waves have often been observed in the dayside magnetosphere, which affects the acceleration and deceleration of energetic particles in inner magnetosphere, and is also responsible for the particle precipitation. There have been few reports of ULF wave activity on the nightside. Here based on the observations of TC-1 in the magnetotail central plasma sheet, two ULF wave events induced by two interplanetary shocks are identified and analyzed. East-west magnetic and radial electric field perturbations, which denote the toroidal mode, are found to be stronger for the two cases and their phase difference are nearly 90°. These features are consistent with previous observations from THEMIS. Several possible mechanisms for these kinds of ULF wave excitation are discussed according to the observational characteristics. It helps to deepen the understanding of the global response of the magnetosphere to interplanetary shocks.
Observation of a Slow Shock Associated with Reconnection Exhaust inside the Boundary Layer of Magnetic Cloud at 1 AU
ZHOU Zilu, ZUO Pingbing, SONG Xiaojian
2020, 40(4): 471-478. doi: 10.11728/cjss2020.04.471
A pair of slow shocks in the Petschek reconnection model facilitate the energy transfer from magnetic field to kinetic and thermal energy of plasmas. In the past decade, a large amount of Petschek-like Reconnection Exhausts (RE) have been reported, but slow shocks bounding the REs are seldom identified. In this paper, a slow shock bounding a reconnection exhaust was identified in the front Boundary Layer (BL) of a Magnetic Cloud (MC) observed by WIND spacecraft on 27 February 2012. The observations of the jump conditions across the shock are in good agreement with the Rankine-Hugoniot relations. The intermediate Mach numbers are less than 1 on both sides of the shock. The slow Mach number is above unit (2.94) in the upstream side but below unit (0.65) in the downstream. The extremely low plasma beta (0.08) in the MC and the occurrence of magnetic reconnection in the MCBL may explain the formation of this slow shock.
Observations of ULF Waves at the Late Recovery Phase of Magnetic Storm
WEI Chao, DAI Lei
2020, 40(4): 479-492. doi: 10.11728/cjss2020.04.479
Two ULF wave events on 25 Jan. and 22 Feb. 2016 are studied by using the combined observations of Radiation Belt Storm Probes (RBSP) and Magnetospheric Multiscale (MMS). Both events occurred in the late recovery phase of the magnetic storm, and both fluctuations occurred in the area between morning and noon. The two events observed by RBSP occurred in the low L-shell (4.7~5.8), and the two events observed by MMS occurred in the high L-shell (8.0~14.2). In the high L-shell, the ULF wave is dominated by toroidal mode, and it is the first harmonic along the field line. In the low L-shell, the ULF wave is dominated by the poloidal wave, and it is the second harmonic along the field line. In addition, by comparing the absolute values of ∂f/∂w|μ,L and (dL)/(dW)(∂f)/(∂L)|μ,W, the bump-on-tail ion distribution and inward gradient of ion phase space density together provide free energy for the wave through N=1 bounce resonance. According to the analysis of these two cases, about 10keV ions exist with the waves and provide free energy for the generation of waves at the late recovery phase of the magnetic storm.
Enhancement of Field-aligned Current during the Azimuthal Flow in the Near-Earth Magnetotail
ZHU Guangzheng, MA Yuduan
2020, 40(4): 493-504. doi: 10.11728/cjss2020.04.493
Past researches have shown that the high-speed flow can evolve into azimuth flow at the near-Earth magnetotail. The magnetospheric counterpart of azimuthal flow and auroral expansion activities in the ionosphere commonly showed features of fast azimuthal and earthward flows in the near-Earth plasma sheet. There are 62 azimuthal flow events when three satellites (THA, THD, THE) of THEMIS were located in the magnetotail from 2016 to 2018, one typical case is selected to study in detail after further investigating of these events. Their relative position and simultaneous observation provide us a good opportunity to further calculate the azimuthal pressure gradient and the radial and the field-aligned current. Our results show that the calculation based on the simultaneous observations of the three satellites are quite different from that obtained by the previous observation of a single satellite in different periods:the value of the radial current from joint observation is much smaller and the average value is only about 15% of the previously single satellite at different times; while the value of the field-aligned current from joint observation exceeds that of single satellite for about 1/3 periods of this event, the peak value is even about one order of magnitude larger than that of a single satellite. Thermal pressure does not vary linearly with azimuth angle but changes sharply within a small azimuthal range. By furtherly investigating the flow field in the xy plane during part periods of this azimuthal flow event, it is found that the magnitude of the field-aligned current had a good correlation with the flow shear simultaneously observed by the three satellites. When the near-Earth magnetotail and the ionosphere are coupled by field-aligned current during the azimuthal flow event, our results show that the field-aligned current is not evenly distributed in wide magnetic local time, but is enhanced shortly in a localized region which is possibly due to strong shear of the azimuthal flow in the xy plane.
Reconstruction Method for the Ionospheric f0F2 at High Latitude Region Based on Kriging Method with Geomagnetic Coordinates
CHENG Huaye, WANG Jian, HUANG Xiangdong
2020, 40(4): 505-512. doi: 10.11728/cjss2020.04.505
As an important part of the solar space environment, the ionosphere state exerts significant impacts on human communication and satellite navigation. The current approach of this modified Kriging reconstruction accuracy of the existing methods needs to be improved. In order to improve the reconstruction accuracy of the ionospheric critical frequency of F2 layer (f0F2) over high latitude regions, a method combining geomagnetic coordinates with modified Kriging interpolation is proposed. A variogram is determined by comparing two types of coordinate systems, two types of ionospheric distance calculation methods and different scale factors. The ionospheric critical frequency is estimated by solving this variogram-related Kriging equation. Cross-validation is implemented on observations recorded during solar maximum activity year (2013) and solar minimum activity year (2017), of four seasons in day and night, and with different scale factors at six ionospheric sounding stations over Russian region. Experimental results showed that the standard errors of the three methods are distributed within 1MHz, and the reconstruction error of the proposed method is reduced compared to the previous methods. Hence the effectiveness of the selected geomagnetic coordinate is verified. In summary, the proposed reconstruction method is of great significance for improving usable frequency prediction and enhancing communication performance.
Error Correction Method of Magnetic Field Gradient Tensor Measurement Based on Vector Magnetometer
DU Yuchen, WANG Jindong, ZHANG Yiteng
2020, 40(4): 513-522. doi: 10.11728/cjss2020.04.513
When the satellite is in orbit, the spacecraft will generate some magnetic interference. Generally, the sensor is installed away from the spacecraft by the extension rod, or the magnetic field gradient measurement method is performed by using multiple magnetic field sensors to eliminate the magnetic interference of the spacecraft. When using a magnetic field gradient tensor to measure the magnetic gradient, the structure of the tensor itself will bring errors to the measurement. In this paper, the error of five main tensor structures is simulated, and the measurement error of the cross-shaped structure is the smallest. In addition to the error of the structure itself, the main error of tensor consists of two parts, i.e. the error of the three-axis magnetometer itself and the misalignment error of the tensor. In this paper, the ellipsoid fitting algorithm is used to correct the error of the magnetometer itself. The measured scale field RMS (Root Mean Square) of the magnetometer is 0.864nT. Aiming at the installation error of tensor, a correction algorithm for misalignment error between orthogonal systems is proposed. The simulation results show that corrected misalignment angle error is ≤ 3.2×10-5 rad and the algorithm can reduce misalignment error of tensor.
Fast Calculation of Magnetic Coordinates Using Artificial Neural Network in Jovian System
WANG Jianzhao, MA Jinan, JIA Xiaoyu, TIAN Dai, ZHANG Qingxiang, LI Yancun, ZHU Anwen, QIU Jiawen
2020, 40(4): 523-530. doi: 10.11728/cjss2020.04.523
In the study of Jovian radiation belt, the accurate calculation of magnetic coordinates from geographic coordinates is the basis. In the previous study, the L-shell parameters are calculated based on the assumption of a dipole field. The accuracy of this method is low. In this study, an L-shell calculation method based on magnetic field line tracing method is presented. The necessity and rationality of this method are also shown. This method is very time-consuming at the high-resolution requirement. In addition, this method is advanced by combining with an Artificial Neural Network (ANN), which can calculation L-shell at a much faster speed. The ANN consists of a classifier and a predictor. The classifier is a BP neural network based on Adaboost algorithm and can identify if the coordinates are within inner magnetosphere. If so, the predictor is used to calculate the L-shell parameter. The predictor is a BP neural network optimized by genetic algorithm. The classification error rate of the classifier is within 3% and the error rate of the predictor is within 7%. In the calculation of the orbit of Juno spacecraft, the calculation speed of this neural network based method is about 3 orders higher than that based on the field line tracing method.
Technology of Biotransformation and Oxygen Production from Perchlorate on the Surface of Mars
LI Yanju, WU Yue, FAN Chunping, NIAN Nian
2020, 40(4): 531-539. doi: 10.11728/cjss2020.04.531
The extreme anoxic conditions on the surface of the Mars and the strong oxidation environment formed by the widespread perchlorate pose a direct threat to the human landing, exploration and the future construction of habitable environment. Based on the current relative research results of perchlorate distribution on the Mars, the research progress of perchlorate biodegradation on the Earth and the demand of resources and environment for human landing on Mars, an assumption and its technology are proposed to use biological method to make oxygen from perchlorate in-situ on the Mars. A forward-looking analysis of oxygen bio-conversion process, influencing factors, key technology and difficulties of bio-conversion in-situ oxygen production, planetary protection and by-product recycling, and the subsequent environmental reformation on Mars are put forward. It is expected to realize at the same time perchlorate harmless treatment and oxygen bio-conversion in cite from perchlorate on the Mars, to turn harm into benefit, to provide new thoughts and feasible methods for the creation of living conditions for human landing and even immigration to Mars.
Inhibitory Effects of Head-down Bed Rest on Bone, Glycolipid Metabolism of Rhesus and Their Correlation Analysis
YANG Chao, XU Zihan, LI Kai, ZHANG Hongyu, WANG Hailong, WU Feng, CAO Hongqing, KAN Guanghan, LI Yinghui, DAI Zhongquan
2020, 40(4): 540-546. doi: 10.11728/cjss2020.04.540
Bone loss and subclinical diabetes-like are developed during long-term spaceflight. Recently, it was demonstrated that bone was able to regulate energy metabolism and testosterone synthesis via osteocalcin. In this study, we analyzed the changes of bone metabolism and glycolipid metabolism of rhesus and their association (P<0.05). Serum insulin and LDL content significantly decreased at 7 days and remained at a low level, and the blood glucose level showed a significant decline at 7 days, but recovery at 21 days. The correlation analysis showed that there was a correlation between osteocalcin and blood glucose, cortisol and HDL. The experimental results show that there is mutual regulation between bone and glycolipid metabolism in the bedrest experiment of rhesus.
Mars Entry Trajectory Quick Optimization Method for Lifting Vehicle Based on Adaptive GPM
SUN Zhiyuan, LIU Zhiyong, ZHANG Peng
2020, 40(4): 547-553. doi: 10.11728/cjss2020.04.547
A new method is given based on adaptive Gauss pseudospectral method for quick trajectory optimization problem of Mars entry. This method converts the trajectory optimization problem to a non-linear programming problem, taking into account for the dynamic constrains, the boundary constrains, the path constrains and the control constrains during the Mars entry of the lifting vehicle. And then, sequential quadratic programming is adapted to solve the non-linear programming problem, and the optimal fuel-consuming trajectory is obtained. In combination with the adaptive Gauss pseudospectral method and sequential quadratic programming in Matlab software, the numerical results of the optimal trajectory with 267 collocations could be obtained in 800s with an approximation accuracy of 10-6. The numerical results are smooth and meet all constrains during the Mars entry process, which suggests that the method introduced in this paper is available and of great practical application.
Optimal Design of Revisit Constellation Based on Coverage Analysis of Low Density Grids Model
MA Yuanye, ZHENG Jianhua, LI Mingtao
2020, 40(4): 554-561. doi: 10.11728/cjss2020.04.554
Fast revisit constellation can quickly obtain the state information of local or global targets, which has the advantages of continuity, and is widely used in the fields of remote sensing, network communication, meteorological observation, near Earth space environment detection. Therefore, it is of great significance to study the optimal design of the fast revisit constellation. Grid point analysis is the most commonly used method in constellation design, but its calculation is large. In this paper a constellation optimization design method based on low-density grid coverage analysis for revisiting constellation optimization design is proposed, which combines the regular polyhedron spherical partition model and the sampling point grouping scheme. This method reduces the computation by more than 80% under the premise of ensuring the accuracy of the design results. Experiments show that the multi-group constellation configuration scheme optimized by this method has good revisit characteristics, and greatly reduces the optimization design time. Moreover, compared with the statistical results of using high-density grid, the error of the optimized design results is very small.
Characteristics of Dynamic Connection and Path Spatial-temporal Evolution in Cluster Flight Spacecraft Network
MO Jinrong, HU Shengbo, SHI Yanfeng, SONG Xiaowei, YAN Tingting
2020, 40(4): 562-571. doi: 10.11728/cjss2020.04.562
The high-speed flight of cluster flight spacecraft modules increases the uncertainty of network topology. In order to optimize the orbital design of the cluster flight spacecraft and improve the performance of Cluster Flight Spacecraft Network (CFSN), the characteristics of dynamic connection and path spatial-temporal evolution was studied by the probabilistic connectivity matrix in CFSN based on the dynamic connection of nodes. First, the mobility model of nodes was established based on twin-satellites mode. And the solution of the nodal distance density function was obtained by adopting empirical statistical method and curve fitting method in the CFSN. Then, the threshold range of nodal connection distance were derived under the constraints of CFSN, and the probabilistic connectivity matrix and spatial-temporal evolution graphs of any time slot in the orbital hyper-period under different threshold were obtained. Finally, using the orbital data generated by STK, the probabilistic connectivity matrix of sequential path of multiple hops between nodes was obtained through the definition of sequential path and a new matrix multiplication. And the characteristics of dynamic connection and path spatial-temporal evolution in an orbital hyper-period were studied. These results can provide theoretical reference for the design and optimization of CFSN.
Fault and Detection Performance Definition of Beidou Satellite Space Signal
WANG Mengli, XU Junyi, XIANG Caibing, YAO Lihao
2020, 40(4): 572-577. doi: 10.11728/cjss2020.04.572
Performance index assignment and demonstration is an important accordance for satellite navigation system, and it is necessary to direct and restrict each system scheme design and project implementation. Integrity and continuity are key service performance indexes, and whether they are satisfied with user requirement depends on the design of SIS (Signal in Space) fault and monitoring performance. In the system index design, the fault rate of satellite signal and the integrity monitoring index of satellite signal are complementary and constrained with each other. It is necessary to realize the comprehensive design according to the index of each link of the system. Taking user integrity and continuity performances as designing accordances, the conversion and distribution relationships among SIS fault times, mean fault probability, fault misdetecting probability, fault alarming probability and hazardous probability are defined. Then calculation and analyzation are implemented aiming at Beidou system and its constellation characters. In the calculation, requirements of user integrity and continuity adopt the ICAO standard, and the level of satellite signal failure refers to the actual operation level of Beidou regional system. Beidou system monitoring performance index under different SIS fault level is analyzed. The research conclusions provide demonstration and design foundation of the reliability index for Beidou global system.
Mission Scheduling of Key Distribution Experiment in Quantum Science Experimental Satellite
ZHANG Jun, YANG Zhenglei, GUO Jiang, FENG Fan, LI Xiaolong, XI Tao
2020, 40(4): 578-583. doi: 10.11728/cjss2020.04.578
The first quantum satellite was launched on 16 August 2016. One of the satellite's important scientific experiments is the quantum key distribution, and its process is more complicated than other common experiments between the ground and space. In this paper, due to the multiple scheduling constraints and high timeliness requirement problem in the key distribution experiment of quantum science experimental satellite, based on analyses of key distribution process and constraints, a constraint satisfaction scheduling model is proposed. Taking the minimum mission completion time as the model's optimization objective, and considering the distribution of optic and data receiving resources, algorithm based on depth first search is proposed, and the problem of tight coupling and high timeliness was solve commendably. Simulation analyses results showed that the proposed model and algorithm are valid, and the interaction requirements between quantum science experimental satellite and the station in key distribution experiment can be satisfied. In future, further study will be made on the optimization of the algorithm.
Passivity Active Disturbance Rejection Collision Avoidance Compliant Control of Dual-arm Space Robot Capture Spacecraft
AI Haiping, CHEN Li
2020, 40(4): 584-594. doi: 10.11728/cjss2020.04.584
The collision avoidance compliant control of dual-arm space robot on-orbit capture of non-cooperative spacecraft is studied. For this reason, a spring class buffer device composed of Rotary Series Elastic Actuator (RSEA) is mounted between the joint motor and manipulator, which functions are as follows. First, the deformation of its buffer spring can absorb the impact energy of the contact and collision phase. Second, combining the reasonable collision avoidance compliant control scheme to ensure that the impact torque of the joints during motion stabilization phase can be limited to a safe range. The dynamic models of the open chain dual-arm space robot with RSEA and the spacecraft before capture are obtained by using the Lagrange approach and Newton-Euler method. Then, based on the impulse theorem, the geometrical and kinematic conditions of closed chain, the integrated dynamic model of the hybrid system is derived. Finally, considering the post-capture unstable closed-chain hybrid system which is caused by the impact effect, a passivity active disturbance rejection collision avoidance compliant control is proposed for the stabilization control. In addition, the joint torques are distributed by the minimum weighted norm theory to ensure the coordinated operation of the manipulators. Numerical simulation verifies the impact resistance performance of the buffer device and the effectiveness of the proposed strategy.
GNSS-R Sea Surface Wind Speed Inversion Based on Tree Model Machine Learning Method
LUO Liming, BAI Weihua, SUN Yueqiang, XIA Junming
2020, 40(4): 595-601. doi: 10.11728/cjss2020.04.595
GNSS-R is a new technique based on GNSS satellite reflection signals, and it can be applied to the inversion of sea surface wind field. The traditional GNSS-R technology inversion of sea surface wind field mainly has waveform matching and experience function. The waveform matching method is time-consuming and computationally intensive; the empirical function method often uses only a small amount of physical observations, which causes waste of additional information and loss of certain inversion precision. The accuracy of the traditional method of wind speed inversion is about 2m·s-1. In order to improve the inversion accuracy of sea surface wind speed, the tree model algorithm decision tree, random forest and GBDT commonly used in the field of machine learning are introduced to predict the sea surface wind speed. The training set and the verification set are constructed by using GNSS-R and ECMWF data. The training set is used for model learning, and the verification set is used to test the inversion effect of the model. The prediction error of decision tree and random forest is about 0.6m·s-1, and the prediction error of GBDT and other algorithms is about 2m·s-1, which meets the requirements of wind speed inversion. Compared with the traditional GNSS-R inversion method, the machine learning tree model algorithm performs better and has stable performance and less error on the verification set. Therefore, the machine learning tree model algorithm can be applied to the sea surface wind speed inversion.
Design of 1553B Encoder and Decoder
LI Xianqiang, AN Junshe, XIE Yan
2020, 40(4): 602-607. doi: 10.11728/cjss2020.04.602
1553B bus is widely used in aerospace because of its high performance in reliability and real time characteristic. In view of the drawbacks of using imported chips to realize 1553B communication, FPGA is used to realize 1553B communication in this paper. In current method, the 1553B decoder can only work when positive and negative signals are input simultaneously. In this paper the decoder is improved to support 3 models:only positive signal input, only negative signal input, both positive and negative signals input simultaneously. The test results show that the design scheme has good uniformity with the scheme that uses imported chips. The 1553B controller which we have fully independent intellectual property right has been tested for large times, and it runs stably and meets the requirements of aerospace engineering.