Table of Content

    25 June 2021, Volume 41 Issue 3 Previous Issue   
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    Research on RF-ion thruster based on discharge chamber uniform model
    YAN Nengwen, GUO Ning, WU Chenchen, GU Zengjie, YANG Zhaolun
    2021, 41 (3):  1-8.  doi: 10.16708/j.cnki.1000.758X.2021.0031
    Abstract ( 167 )   PDF (4468KB) ( 114 )   Save
    A uniform model of RFion thruster discharge chamber was established to research the discharge principles and regulations among RFion thruster working parameters, geometry parameters and its discharge performances. The solution of model and conclusions of test is compared in the paper. It is found that by reducing the aspect ratio or increasing the mass flow rate, the grid voltage and the RF power can increase the thrust beam current and improve the thruster performance. Test and simulation results show that the discharge chamber uniform model can be used to study the performance of RF ion thrusters.
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    Transfers analysis of deploying a retrograde GEO monitorsatellite by Moon swing-by
    HE Boyong, MA Pengbin, DU Weibing, LI Hengnian
    2021, 41 (3):  9-15.  doi: 10.16708/j.cnki.1000.758X.2021.0032
    Abstract ( 81 )   PDF (2358KB) ( 34 )   Save
    Retro-GEO refers to the retrograde geostationary Earth orbit (GEO), which has the same or similar height as that of the GEO, but with an inclination of 180 °. A monitorsatellite on retroGEO can give early debris warning for the GEO assets every 12 hours. RetroGEO launched directly in the westward has great difficulties in ground tracking and control, as well as launch energy cost. Based on a four body model, and in order to reduce the sensitivity of design variables, a transfer to retro-GEO design model by the Moon swing by was proposed applying the trans-lunar orbital elements at the moment of perilune. The result obtanined by using orbital dynamics model continuation shows a natural property of such orbits, that is the return duration from perilune must be about 114.79 hours. The conclusion can be used to solve this kind of orbit with a high precision orbital dynamics model.
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    Low-light image enhancement of space satellites based on GAN
    CHEN Yulang, GAO Jingmin, ZHANG Kebei, ZHANG Yang
    2021, 41 (3):  16-23.  doi: 10.16708/j.cnki.1000.758X.2021.0033
    Abstract ( 83 )   PDF (3637KB) ( 24 )   Save
    Aiming at the problem of serious information damage of satellite optical images under the lowlight imaging condition, we proposed a satellite lowlight image enhancement method based on GAN. The method can improve the average brightness and contrast of images, restore image details, and provide higherquality information for image processing techniques such as image recognition. Firstly, we designed a densely connected generator to strengthen the information propagation and fusion between each feature extraction phase, reduce the loss of feature, and better extract similar semantic information in normallight and lowlight images. Combining the idea of EnlightenGAN, the globallocal discriminator structure was introduced to enhance images more naturally. Under the condition of a small number of samples, unpaired training was used to the proposed method, and data enhancement methods such as random scaling and flipping of the input images were applied to improve the training effect and model performance. Finally, the proposed method was validated by simulation. The experimental results show that, under the condition of low illumination, the proposed method reduced NIQE by 1.034 and 0.699 compared with the LIME and EnlightenGAN. The proposed method can preserve more image details, realize higher overall and local brightness, higher contrast, and more natural effects of enhancement.
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    Study on discharge life characteristics of micro-cathode arc thruster
    WANG Wenqian, LIU Xiangyang, WANG Shuai, CHEN Shichang, ZHAO Zijing, GENG Jinyue, SHEN Yan, WANG Ningfei
    2021, 41 (3):  24-30.  doi: 10.16708/j.cnki.1000.758X.2021.0034
    Abstract ( 167 )   PDF (8055KB) ( 81 )   Save
    Microcathode arc thruster (μCAT) has a good application prospect in micronano satellite space missions, but the life span is an important factor restricting its development at present. An automatic data acquisition system was developed, and the whole life tests at different discharge frequencies were carried out. The morphology changes of cathode materials and conductive films after failure were observed and analyzed. The results show that, at the initial stage of the thruster, the discharge characteristic is an unstable stage, which accounts for less than 10% of the whole life of μCAT. The discharge of thin film resistance is relatively stable in the early stage, which is of the order of several hundred euros, and increases rapidly to the order of thousands of euros when it is close to failure, and the peak current decreases sharply until failure. The increase of discharge frequency makes the heat accumulation in the cathode pit area, enhances the breakage of the conductive film, leads to the early failure of the thruster and reduces the life of the thruster. The uneven distribution of arc ablation position leads to the decrease of cathode utilization, which is an important factor restricting the life of μCAT.
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    Research on online capability assessment and autonomous planning technology based on indirect method
    ZHAN Kangyi, CHEN Haipeng, HE Congyuan, GAN Qingzhong, WANG Lu
    2021, 41 (3):  31-38.  doi: 10.16708/j.cnki.1000.758X.2021.0035
    Abstract ( 45 )   PDF (4279KB) ( 32 )   Save
    Aiming at the autonomous rescue mission under the thrust failure condition of the launch vehicle, an online capability assessment and autonomous planning method was studied based on the indirect method. The optimal control problem with the maximum energy at the orbit injection point was constructed. Under the constraints of the inclination of the orbit and the path angle of the orbit injection point, the relationship between the speed of the orbit injection point, the height of the apogee, the height of perigee and the height of the orbit injection point was discussed through a numerical method. A feature quantity was designed to perform the orbital capability evaluation. Taking the highest perigee height as the selection criterion for rescue orbit, an autonomous online planning strategy was proposed based on the orbital capability evaluation. When it was judged that it can enter the circular orbit, the secant method was used to solve the largest circular orbit. Otherwise, the Newton method was used to solve the highest elliptical orbit. Simulation results show that the autonomous planning method proposed meets the requirement of online guidance in terms of effectiveness, convergence and realtime performance.
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    Coexistence of GEO and LEO satellite spectrum based on cognitive radio
    HU Xiaoyue, YANG Miao, KANG Kai, ZHANG Shunqing
    2021, 41 (3):  39-45.  doi: 10.16708/j.cnki.1000.758X.2021.0036
    Abstract ( 39 )   PDF (2565KB) ( 25 )   Save
    With the development of new broadband multimedia services, the demand for broadband wireless spectrum has been growing rapidly, which makes spectrum resources scarcer. Meanwhile, low Earth orbit (LEO) satellites deployed on a large scale have the advantages of low transmission loss and small propagation delay. To improve the spectrum utilization rate, a coexistence scheme of geostationary Earth orbit (GEO) satellites and LEO satellites was adopted. In order to avoid the interferences of LEO satellites to GEO satellites during spectrum coexistence, an algorithm combining spectrum sensing and beam hopping was proposed. First, the signaltonoise ratio (SNR) of LEO satellite communication was estimated. Then the optimal threshold was selected according to the estimated SNR. An energy detection algorithm based on dynamic threshold was used to discriminate between the GEO satellite signals, and the beam adjustment was carried out according to the judgment results. Simulation results show that the error of the energy detection algorithm based on the dynamic threshold proposed is significantly lower than that of the traditional energy detection algorithm based on fixed threshold and spectrum sensing method based on secondorder cyclic statistics. When the signal to noise ratio is lower than -10dB the detection error is lower than 0。2, and when the signaltonoise ratio is higher than -5dB the detection error approaches zero.
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    Influence of forward data access modes on navigation constellation network communication performanc
    WANG Qi, SHAO Fengwei, GU Yanan
    2021, 41 (3):  46-51.  doi: 10.16708/j.cnki.1000.758X.2021.0037
    Abstract ( 47 )   PDF (1807KB) ( 12 )   Save
    The influence of forward data access modes on the timedivision polling chainbuilt navigation constellation intersatellite link network data interchange mechanism and communication performance was analyzed, based on which the evaluation and suggestion for the current forward data access application were given. Firstly, the satellite-satellite-station data interchange mechanisms of the quickest path and the fixed node forward data access modes were analyzed, and the corresponding topology and routing planning strategy were given. Secondly, based on the data processing models and typical simulation scenarios of the Walker 24/3/1 global navigation constellation and stations, the simulation and analysis of communication performances of capacity and transmission delay was carried out on the quickest path and the fixed node access modes, and the characteristics of network communication performance and data congestion on the two modes were compared. It is concluded that the quickest path mode has obvious advantages over the fixed node mode in communication performance. Lastly, the advantages and prices for application of the two data interaction mechanisms were evaluated, and the suggestion on proper application of the fixed node forward data access mode was given under the conditions of low communication capacity, low communication delay and high reliability.
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    Technical project of ion propulsion for satellites in super low Earth orbit 
    YANG Fuquan, WANG Chengfei, HU Jing, ZHANG Hong, WU Chenchen, ZHANG Xingmin, GENG Hai, FU Danyin
    2021, 41 (3):  52-59.  doi: 10.16708/j.cnki.1000.758X.2021.0038
    Abstract ( 235 )   PDF (3138KB) ( 223 )   Save
    The Earth's outer atmosphere at the low altitude causes a significant drag on the spacecraft such as scientific detection and Earth observationsatellites in super low earth orbit, furthermore the atmospheric drag changes in a wide range along with solar activity, geomagnetic activity, seasonal and diurnal cycle. In order to meet the demands for satellite orbit accuracy or flight conditions, this drag needs to be continuously or intermittently compensated by onboard thrusters. Considering drag free flight and orbit maintenance at an altitude of about 220~268km, the variety of atmospheric drag and the specifications of the spacecraft payloads were analyzed, and then the researches were carried out on the technical parameters, thrust throttling approaches, system architecture, thrust control project and onorbit application strategy of ion propulsion. Accordingly thrust throttling tests were executed .The results show that ion propulsion should operates over a thrust range of 1~20mN with the thrust resolution of 12μN, and over a thrust range of 1~25mN with the thrust resolution of 100μN for drag free and orbit maintenance mission respectively.The technical project of ion propulsion is valuable for application reference of satellites in super low Earth orbit. 
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    An autonomous integrity monitoring method of integrated navigation based on multiple virtual observations #br#
    WU Kongyang, YE Xiaozhou, XIAO Wei, LIU Wenxiang, LIU Xiaohui
    2021, 41 (3):  60-69.  doi: 10.16708/j.cnki.1000.758X.2021.0039
    Abstract ( 41 )   PDF (3739KB) ( 15 )   Save
    Integrity can provide timely warning in the event of a navigation system failure, which is an important performance indicator for users to consider life safety. This paper is based on the autonomous integrity monitoring algorithm of satellite navigation assisted by the inertial navigation system (INS). An autonomous integrity monitoring method for integrated navigation system was proposed. This method uses INS to construct three-virtual-satellite observations, and can realize fault detection under the condition of two visible satellites by constructing three satellites perpendicular to each other in the line-of-sight direction and using the navigation information of INS to the maximum extent. This improves the availability of detection algorithm compared with the traditional receiver autonomous integrity monitoring (RAIM). The fault detection probability of traditional weighted RAIM is 48.51% under the condition of GPS single constellation and INS positioning error variance σs=1m with the addition of 35m fault of single satellite. The detection probability of the algorithm proposed in this paper is 95.21%, and the detection performance is improved by 47%. This method also has a higher detection probability than the INS-aided Kalman filtering innovation method with the same INS accuracy. In addition, the influence of INS precision on the fault detection performance of this method was simulated and analyzed. The results show that the higher the INS precision is, the better the detection performance of the proposed method is.
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    Short-arc correlation analysis method based on optical observations only
    JIANG Ping, ZHANG Yasheng, TAO Xuefeng, XU Can, FANG Yuqiang, LI Zhi, WANG Hao
    2021, 41 (3):  70-81.  doi: 10.16708/j.cnki.1000.758X.2021.0040
    Abstract ( 41 )   PDF (6974KB) ( 23 )   Save
    The initial orbit determination is important to cataloging the space objects. It is challenging to determine the initial orbit using optical anglesonly observations effectively. A prominent method to solve the shortarc problem is to correlate and match the shortarcs obtained at different times to find observations from the same object. Based on the admissible region, the minimum error between the predicted sequence and the actual observation sequence was calculated by finding the optimal orbit to fit multiple optical observations. Then, based on the study of the statistical characteristics of observation errors, the feasibility of the linearized error propagation method in applying shortarc observations was theoretically verified and a reasonable error limit was given. The chisquare test was used to determine the correlation between shortarcs. At the same time, the results applying the proposed shortarc correlation analysis method to LEO, HEO, MEO and GEO orbits were given. The difficulty of applying in the longinterval loworbit object observations was described. Aiming at resolving this difficulty, a method was proposed to improve the loworbit observations association using the error characteristic law of the angle predicted value. The results show that the success rate of correlation recognition for LEO shortarc observations has increased from 87% to 99%.
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    Design and analysis of the configuration of deployable membrane sunshield#br#
    TONG Zhaoyuan, LI Meng, CUI Chengbo, HUO Zhuoxi, LUO Baorui
    2021, 41 (3):  82-88.  doi: 10.16708/j.cnki.1000.758X.2021.0041
    Abstract ( 57 )   PDF (6277KB) ( 50 )   Save
    For the optical system of MEAYIN mission, stray light from the sun is one of the most significant factors affecting image quality. Through the combination of bionic technology and origami theory, the deployable membrane sunshield for the optical system was designed. The topological configuration of the sunshield and the design of the folding method of the sunshield were obtained according to the blooming process of the flower, and the topological configuration of the hood was optimized based on the task requirements of the optical system. The topological configuration with a regular hexagon bottom surface was adopted, and therefore the foldout ratio of the membrane sunshield was 8, and the folded envelope space coincided with the space occupied by the satellites which made better use of the space. The choice of two layers of membrane as the shading structure not only improved the shading performance, but also made sure that the sunshield had a certain heat insulation function, which protected the optical system better. Finally, ABAQUS was used to simulate the single layer membrane unfolding process, and the stress level was analyzed. The result shows the unfolding process of the sunshield membrane is smooth, and the maximum stress after deploying is 40.63MPa which is under the stress strength of Kapton membrane.
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    Fault diagnosis for momentum wheel bearing based on spectral kurtosis entropy and hierarchical extreme learning machine
    LIU Luhang, ZHANG Qiang, WANG Hong, LI Gang, WU Hao, WANG Zhipeng, GUO Baozhu, ZHANG Jiyang
    2021, 41 (3):  97-104.  doi: 10.16708/j.cnki.1000.758X.2021.0043
    Abstract ( 85 )   PDF (6598KB) ( 16 )   Save
    The momentum wheel is the key component of the satellite attitude control system, and its reliability is directly related to the life and safety of the whole satellite. As the core component of momentum wheel, bearing is prone to failure. Due to its unique structure and complex operating environment, the signal to noise ratio of monitoring signals is low, and early fault diagnosis is difficult. Aiming at this situation, a feature extraction method combining variational mode decomposition and kurtosis entropy was proposed to obtain the weak fault features of momentum wheel bearing monitoring signals and to establish the feature vectors. The layered extreme learning machine was introduced, and the structure and coding method were optimized for bearing fault identification. Finally, the proposed method was applied to the actual fault diagnosis. The comparison with the traditional ELM method shows that the proposed method has higher diagnostic accuracy (98.5%) in the fault diagnosis of momentum wheel bearings.
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    Load balancing heterogeneous path algorithm for satellite hybrid switching system
    LI Jingling, LI Jun, ZHANG Yi, CUI Tao, LIANG Wei
    2021, 41 (3):  105-113.  doi: 10.16708/j.cnki.1000.758X.2021.0044
    Abstract ( 59 )   PDF (4332KB) ( 18 )   Save
     For both optical and packet heterogeneous paths existing in satellite opticalelectrical hybrid switching system, the method of independently calculating the optical/packet switching path can′t comprehensively consider the availability of the system's path resources, which may lead to the selection of unoptimized switching paths with high paths blocking probability, even may cause a crash of the switching system. The homogeneous path influence factor and the heterogeneous path influence factor were defined to quantitatively measure path weights. In addition, the number of subpaths and the path transformation parameters of the switching system were used as constraints. Then, by constructing a heterogeneous path resource weight function, the load balancing capability of the paths in the satellite heterogeneous switching system was accurately evaluated. Moreover, the indicators of load balancing degree and the path blocking probability were simulated based on switching structure simulation model by using MATLAB and OMNET. The simulation results show that, compared with traditional routing and wavelength assignment algorithms, the load balancing heterogeneous path algorithm can achieve stable performance curves under deterministic service requests and effectively reduce the average load balancing degree of the system by about 32% and the average path blocking probability by about 51% under a specific service request. 
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    Research on satellite optical axis compound pointing control method
    YAN Nanxing, LIN Zhe, LIU Yaning, YU Fei, WANG Chun, KANG Jianbing
    2021, 41 (3):  114-122.  doi: 10.16708/j.cnki.1000.758X.2021.0045
    Abstract ( 60 )   PDF (4284KB) ( 20 )   Save
    Tracking moving target in space with optical payload on satellite platform has been a key technology in the development of surveillance satellite. How to improve the pointing range, tracking accuracy and maneuverability of satellite optical axis is the focus of this paper. In order to improve the performance of satellite optical axis pointing, the scheme of satellite attitude adjustment can′t meet the requirements alone. The analysis shows that, in order to improve the pointing range, tracking accuracy and maneuverability of the satellite optical axis, the effective cooperation of the satellite attitude control system, optical turret control system and fastmirror control system is necessary. The satellite attitude control system, optical turret control system and fast-mirror control system were analyzed and modeled to confirm the bandwidth of each system. A compound pointing compensator was designed with the frequency response method through the PQ feedback system. The relative motion trajectory of the satellite and the target was simplified and simulated. The simulation data show that the tracking error is reduced from 0.6° to 0.05°, the effectiveness of the optical axis compound pointing control method is verified. 
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