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    Feasibility analysis of airbreathing plasma propulsion system
    YANG Zhaolun, GUO Ning, CHEN Xuekang, YAN Nengwen, WANG Cong
    Chinese Space Science and Technology    2020, 40 (1): 54-.   DOI: 10.16708/j.cnki.1000-758X.2020.0007
    Abstract400)      PDF(pc) (1591KB)(351)      
    The airbreathing plasma propulsion system has been studied as a potential technology for longlife super low altitude flight. According to different orbital environmental conditions, the feasibility of the airbreathing plasma propulsion system was discussed by using the tubular inlet and the mechanical pressurization suction method. The analysis shows that the ratio of the total power required by the spacecraft to the windward surface should be greater than 2kW/m2, and that the specific impulse of the plasma thruster should be greater than 4×104m/s, so as to meet the requirements of pushdrag balance. It is pointed out that in order to realize the application of suction system in earth orbit, the key technology is to increase gas collection efficiency and reduce collection power consumption, while the efficiency of plasma thruster needs to be further improved.
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    Verification on electromagnetic vector modulation of plasma flow generated in helicon plasma thruster#br#
    DING Liang, ZHENG Huiqi, PENG Yuchuan, REN Qiongying, ZHAO Hua
    Chinese Space Science and Technology    2020, 40 (4): 38-43.   DOI: 10.16708/j.cnki.1000-758X.2020.0043
    Abstract359)      PDF(pc) (10374KB)(153)      
    The electromagnetic vector modulation of electrical thruster′s flow is based on magnetic field reforming which leads to the orientation altering of plasma flow. To verify the electromagnetic vector modulation of electrical thruster, the theoretical simulation and experiments were carried out for the helicon plasma thruster (HPT). The magnetic field can be altered with electromagnetic vector modulation coils illustrated in theoretical simulation results. The plasma flow is deflected as the magnetic field is adjusted as shown in experimental results. Plasma density fluctuates according to an accessional magnetic field generated periodically. The plasma flow changes its orientation with 60 degrees at most with a modulated frequency which reaches 15Hz. The electromagnetic vector modulation for helicon plasma thruster is verified feasible.
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    Parameter selection and control of field emission electric thrusters
    LIU Zijian, SHEN Yan, GENG Jinyue, LIU Xuhui, QIN Yu
    Chinese Space Science and Technology    2020, 40 (4): 1-10.   DOI: 10.16708/j.cnki.1000-758X.2020.0039
    Abstract324)      PDF(pc) (5166KB)(244)      
    Field emission electric thrusters have different working modes, and can produce either droplets or ions. The thrust parameters change widely due to different charge to mass ratio of the charged particles.For different space applications, different types of field emission electric thrusters need to be designed to achieve the corresponding thrust parameters. The emission process of the thrusters and the selection and control method of the thrust parameters were discussed. The basic working principle of field emission electric thrusters and each working mode were discussed. The calculation results show that different emission modes can be achieved with different propellants, followed by the conclusion that the thrust parameters are controlled by the propellants′ species, extract voltage and propellant flow rate, etc. Design and experiment results of an ionic liquid electro spray thruster show that the thrust and specific impulse produced by the thruster can be modified by changing the applied voltage. The thrust and specific impulse can reach 16~10μN and 154~978s respectively.
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    Research on CEI phase delay resolving method for BDS GEO satellite
    CHEN Shaowu, WANG Jingwen, HUANG Lei, XU Dezhen
    Chinese Space Science and Technology    2020, 40 (6): 123-130.   DOI: 10.16708/j.cnki.1000-758X.2020.0079
    Abstract310)      PDF(pc) (3537KB)(258)      
    Connected element interferometry (CEI) is a precision angular measurement technology widely used in the orbit determination of MEO satellites, GEO satellites, lunar probes and deep space probes. A new measurement mode was proposed based on the characteristics of CEI. The carrier and ranging signals in coherent ranging mode were used in CEI. A CEI system was established and used to observe BDS (BeiDou navigation satellite system) GEO satellite. Group delay and phase delay were calculated by using all these signals. Group delay and phase delay results of the BDS GEO satellite were estimated by using the theoretical delay values calculated by precision ephemeris. The results show that the means of the residual of group delay and phase delay is 0.47ns and 0.08ns, and that the standard deviation (3σ) of the residual of group delay and phase delay is 4.2ns and 0.13ns. The feasibility of the phase delay calculation of CEI in coherent ranging mode is verified. This paper can provide reference for precision orbit determination of co-location GEO satellites, lunar probes and deep space probes.
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    High specific impulse Hall thruster startup characteristics
    CHEN Jie, KANG Xiaolu, ZHAO Zhen, CHENG Jiabing, LIANG Wei
    Chinese Space Science and Technology    2020, 40 (4): 22-28.   DOI: 10.16708/j.cnki.1000-758X.2020.0041
    Abstract280)      PDF(pc) (4663KB)(184)      
    High specific impulse Hall thrusters have been valued from the early stage of the development of Hall thrusters, but there are few studies on parameter comparison, current changes and oscillation characteristics related to engineering applications. The performance and startup characteristics of HET80HP high specific impulse Hall thruster were given by measuring the thrust, current variation and oscillation of the thruster under different working conditions. The research results show that HET80HP high specific impulse Hall thruster has better performance than the traditional Hall thruster under the conditions of large flow rate and high discharge voltage. During cold start, there is a current spike in the discharge current under normal magnetic field conditions, and the current takes a long time to achieve relative stability. The variation of current during the hot start of different magnetic field configurations indicates that the presence of current spikes is mainly related to the magnetic field configuration and has no obvious relationship with the startup  temperature. In addition, by comparing the difference in thruster specific impulse and average frequency under different magnetic fields, it can be seen that the average frequency of lowfrequency oscillation of thruster can better reflect the magnitude of thruster specific impulse.
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    Numerical study of electromagnetic acceleration mechanism for pulsed plasma thruster
    YANG Sanxiang, LIU Chao, WANG Shangmin, FENG Jie, CHEN Juanjuan, WU Chenchen, JIA Yanhui, GUO Ning, GENG Hai
    Chinese Space Science and Technology    2020, 40 (4): 11-21.   DOI: 10.16708/j.cnki.1000-758X.2020.0040
    Abstract275)      PDF(pc) (12440KB)(186)      
    In order to get a clear understanding of electromagnetic acceleration mechanism for pulsed plasma thrusters, and offer a theoretical foundation for the performance optimization and minification of the thruster,numerical simulation of the pulsed plasma thruster characteristic is necessarily to be researched. In this paper, a onedimensional integrated circuit model that includes the capacitance, inductance, electrodes and plasma is used to numerically study pulsed plasma thrusters. The electromagnetic acceleration mechanism of pulsed plasma thrusters is systematically investigated by varying the initial discharge voltage and separation distance of the electrodes. The results show that the thrust, specific impulse, impulse bit of pulsed plasma thrusters, and temperature and density of plasma increase with initial discharge voltage. Similarly, the thrust and specific impulse of thrusters also increase with the separation distance of electrodes. However, the igniting difficulty of thruster increases since the resistance between electrodes increases with the electrodes spacing. Therefore, there is an optimal value of distance between electrodes of the pulsed plasma thruster. 
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    Design of satellite-borne microwave photonic mixer based on DDMZM
    HUI Jinxin, ZHAO Ying, DENG Xiangke, ZHENG Feiteng, SUN Shufeng
    Chinese Space Science and Technology    2020, 40 (3): 36-42.   DOI: 10.16708/j.cnki.1000.758X.2020.0030
    Accepted: 19 February 2020

    Abstract236)      PDF(pc) (2308KB)(97)      
    Due to the influence of distributed parameters on microwave components, there is certain frequency selectivity, and it is difficult to achieve the broadband and multi-band compatible frequency conversion system, which can no longer meet the needs of the high-throughput satellite communication payload. Microwave photonics technology provides the possibility of realizing high-throughput satellite communication needs with its advantages of large bandwidth and no frequency selectivity. Based on dual-drive Mach-Zehnder modulator (DDMZM), the solution of the frequency conversion unit of the satellite communication system was explored. Through theoretical analysis of the link model, the software VPI was used to simulate and optimize the link to find the best offset point of the DDMZM. The experimental results show that when the modulator is biased at the minimum point, the frequency conversion efficiency is high, and it has certain carrier suppression function, which can achieve broadband, multi-band and anti-interference performance,and is superior to microwave frequency conversion performance.
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    GEO satellite communication link budgets calculation and analysis
    XU Ting, LAN Hai, ZHANG Hongjiang
    Chinese Space Science and Technology    2020, 40 (3): 83-92.   DOI: 10.16708/j.cnki.1000-758X.2020.0035
    Accepted: 20 January 2020

    Abstract228)      PDF(pc) (3338KB)(159)      
    As an important technology, satellite-ground link budget calculation is the theoretical basis of satellite communication system designing which directly decides the link availability. As there are many factors which may affect the satellite link, any unreasonable factor in the design would make the whole satelliteground link unavailable and leads to a big loss. Moreover, there is no ideal satellite link situation unless overlooking some factors, which is also a difficulty during the link budget calculation. Based on the international common calculating method, GEO satellite link was analyzed thoroughly, separating the whole link into uplink and downlink. Then a practical example was analyzed and calculated according to the project experience in LAOSAT Company. At last, different reasonable designing methods in terms of different link configurations were obtained, which could be the references to link calculation and analysis of GEO satellite communication.
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    Effect of temperature on magnetic field configuration of magnetically shielded Hall thruster#br#
    ZHAO Zhen, CHENG Jiabing, KANG Xiaolu
    Chinese Space Science and Technology    2020, 40 (4): 29-37.   DOI: 10.16708/j.cnki.1000-758X.2020.0042
    Abstract227)      PDF(pc) (6885KB)(81)      
    Magnetostatic simulation in room temperature condition is mostly applied for Hall thruster design and verified with measurement in non-working state. Severer thermal issues will be addressed for larger power Hall thrusters and result in magnetic deviation under high temperature. In order to study thermal influence, 10kW Hall thruster thermomagnetic coupling simulation was carried out. Comparing both results, discrepancy of magnetic radial component on Br centerline near anode was larger than that in exit. Magnetic shielding obtained in room temperature simulation was deviated in thermal state with non-compliance between field and wall up to 13%, through wall shape recorrection, magnetic shielding was restored with noncompliance below 4.8%. Reasonable design reduced thermal loads. Simulation showed that the maximal circuit temperature was less than 500℃, lower than 0.78 times of Curie temperature, which would not lead to sharp drop in magnetic performance, but thermal impact on magnetic configuration needs to be considered in magnetic shielding simulation.
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    Ionospheric VTEC fusion based on BP neural network technology
    GUO Chengjun, PANG Guoqiang
    Chinese Space Science and Technology    2020, 40 (4): 78-83.   DOI: 10.16708/j.cnki.1000-758X.2020.0048
    Abstract218)      PDF(pc) (3366KB)(61)      
    With the continuous development of ionospheric detection technology, there are more ionospheric observation data. Using only a single observation datum will cause the problem of low accuracy of ionospheric inversion. In order to improve the inversion accuracy of the ionosphere, the BP neural network technology is used to effectively fuse the vertical total electron content (VTEC) data of ground-based inversion and international reference ionosphere (IRI) model inversion. Ionospheric inversion experiments were performed in temperate regions [35°(N)--45°(N),60°(E)--80°(E)\]. The results show that the data fusion based on BP neural network technology and ground-based inversion can both achieve high accuracy of ionospheric VTEC. The data fusion method based on BP neural network has higher ionospheric inversion accuracy than ground-based inversion, so data fusion based on BP neural network technology can improve the ionospheric inversion accuracy.
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    A high accuracy pointing control method for space target
    FENG Tiantian, GAO Jingmin
    Chinese Space Science and Technology    2020, 40 (2): 1-.   DOI: 10.16708/j.cnki.1000-758X.2020.0013
    Abstract213)      PDF(pc) (3717KB)(157)      
    In order to meet the requirement of high accuracy control for satellites in space moving target pointing missions, the control method of the twolayer attitude system by the spacecraft base and fine steer mirror (FSM) are considered. The high accuracy pointing control method for space moving targets is presented. First, the position information of tracking satellite and target satellite was obtained based on the ClohessyWiltshire equation of the nearcircular orbit. Then, the multiple information fusion extended Kalman filter was adopted to estimate tracking satellite attitude. The relative attitude between tracking satellite optical axis and target satellite was calculated in real time so as to obtain the azimuth and elevation angle required for tracking and pointing control. Finally, fast and high accuracy pointing to the target satellite was realized through spacecraft base firstlayer attitude control and payload optical axis secondlayer pointing control based on FSM. Simulation results show that the proposed method can keep dynamic pointing error less than 072″. The method presented can realize high accuracy tracking and pointing control of space target and can provide technical support for space missions such as laser communication.
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    Emergency return analysis of hybrid trajectory based on one impulse for human lunar mission
    LYU Pengwei, SHANG Zhi, WANG Ping
    Chinese Space Science and Technology    2020, 40 (1): 1-.   DOI: 10.16708/j.cnki.1000-758X.2020.0001
    Abstract211)      PDF(pc) (3881KB)(155)      
    For human earthmoon transfer mission, emergency return trajectories are key to astronauts′ safe return to earth. Emergency return trajectories based on human translunar hybrid trajectory were proposed, considering safety the most important requirement in human earthmoon transfer mission. There are three emergent return methods,which are direct return, immediate transfer and steer by the moon, and steer by the moon and return. The characteristics of transfer time and velocity increment of the three emergent return methods were studied. The advantages and disadvantages of the three emergency return methods were analyzed, providing reference for translunar trajectory selection in subsequent human lunar exploration missions.
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    Study on maneuver methods of satellites constellation with continual small-thrust propulsion
    YANG Shengqing, WANG Yu, WANG Danna, LIN Rongfeng, DU Yaoke, ZHONG Chao
    Chinese Space Science and Technology    2020, 40 (4): 69-77.   DOI: 10.16708/j.cnki.1000-758X.2020.0047
    Abstract209)      PDF(pc) (4819KB)(91)      
    Based on the orbit dynamic characteristics, orbit maneuver methods of satellites constellation with continual small-thrust propulsion are studied in this paper. Because of the huge scales of constellations, orbit maneuver of constellation in near-earth orbit can hardly be managed by traditional method as trajectory planning. Orbit insertion for constellation configuration is considered as a relative semimajor axis control problem in timedelay maneuver sequence. Meanwhile, offset control of inclination is considered for drift of right ascension of ascending node(RAAN) during arisingorbit maneuver. For consideration of orbit discarded problem, a unitedcontrol for combination of semimajor axis and eccentricity is designed for a rapid orbit decay with energy-saving. Because of the curveeffect for continual smallthrust propulsion, curvilinear integral of orbit control should be investigated for all the strategy optimizations.
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    Influence of 3D regular surface morphology on secondary electron emission
    ZHANG Na, CUI Wanzhao, CAO Meng, WANG Rui, HU Tiancun
    Chinese Space Science and Technology    2020, 40 (3): 1-7.   DOI: 10.16708/j.cnki.1000.758X.2020.0025
    Accepted: 04 March 2020

    Abstract206)      PDF(pc) (3603KB)(106)      
    It has been applied in many fields to customize specific surface morphology to control secondary electron emission of materials.The regular surface morphology can easily reveal the influence of the suppression and the influence mechanism on the secondary electron emission. Meanwhile, photolithography, plasma etching and other processes can better achieve the specific design of regular morphology. Therefore, custom regular morphology is often used in the initial research stage of multipactor or in the process of principle experimental verification. Taking the threedimensional cylindrical hole as an example, multi-generation Monte Carlo method which considers multiple interactions between electrons and complex surface morphology was used to systematically study the influence of regular morphology parameters such as depthwidth ratio and duty cycle ratio on secondary electron yield (SEY), secondary electron spectrum (SES) and emission angle distribution. It was found that the larger the depthwidth ratio of regular morphology is, the wider the SES broadening, the stronger the selectivity of the morphology to emission angle, and the better restraint effect of SEY, but the restraint effect is not indefinite. When the morphology does not overlap, SEY can also be effectively reduced by increasing the duty cycle ratio. However, due to the relatively small proportion of emitted electrons of the cylindrical hole compared with flat surface, the SES and the emission angle distribution is close to flat surface. The secondary electron emission properties of regular morphology obtained in the paper provide a reference for the comprehensive evaluation of its influence on multipactor effect.
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    Research on passive intermodulation based on broadband modulation signal
    LI Yanping, HUANG Hao, HE Jie
    Chinese Space Science and Technology    2020, 40 (3): 13-18.   DOI: 10.16708/j.cnki.1000.758X.2020.0027
    Accepted: 17 February 2020

    Abstract202)      PDF(pc) (1204KB)(123)      
    With the extensive use of transmitter-recevier sharing and digital modulation (BPSK,QPSK) technologies in satellite communication, there are insufficient verification problems in the original continuous wave (CW) and passive inter modulation (PIM) test system. In this paper, a broadband digital signal PIM test method was designed by using the channel power to test PIM. The test results show that digital modulation PIM values of both BPSK and QPSK signals are higher than the CW carriers by 2~9 dB. Considering the operational reliability of the satellite, the digital modulation working mode was adopted to improve the original test system and the new test is closer to the pracical work, which improves the reliability of ground verification.
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    Ballistic coefficient estimation method based on TLE and application analysis
    ZHANG Wei, CUI Wen, ZHANG Yuwei, LIU Xing, ZHU Jun
    Chinese Space Science and Technology    2020, 40 (3): 107-113.   DOI: 10.16708/j.cnki.1000-758X.2020.0038
    Accepted: 20 January 2020

    Abstract201)      PDF(pc) (3008KB)(120)      
    In order to meet the requirements of research which use two line element (TLE) as data source, ballistic coefficient estimation methods based on the variation in mean semimajor axis derived from TLE were studied. A direct estimation method based on two TLEs was introduced, and the influence of the TLE interval on the ballistic coefficient result accuracy was analyzed. In order to reduce the influence of outliers, an iterative estimation method based on multiple TLEs was proposed. Comparative analysis was made for these two methods. The results show that these two methods have their own advantages and disadvantages. The ballistic coefficient results estimated by the iterative method have higher stability and are less affected by the TLE accuracy. Due to the shorter data interval, the estimation results using the direct method respond more accurately to the short-term orbital variation characteristics, and this method is recommended to be used in the last phase of re-entry.
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    Cfield optimization for magnetic state selection of cesium beam tube based on PID algorithm
    CHEN Shi, WANG Ji, HUANG Liangyu, LIU Zhidong
    Chinese Space Science and Technology    2020, 40 (2): 54-.   DOI: 10.16708/j.cnki.1000-758X.2020.0020
    Abstract197)      PDF(pc) (3810KB)(93)      
    Optimization for Cfield of magnetic state selection cesium beam tube was introduced. The test system developed for cesium beam tube provided the necessary test environment, and different kinds of PID control algorithms were designed to optimize and analyze Cfield of cesium beam tube. Finally a more reasonable optimization parameter was obtained. By optimizing multiple cesium beam tubes, the frequency difference between the (0~0) peak and ±1 peak of the cesium beam tube was controlled within the range of 42820kHz ± 20Hz. By comparison with the results from an earlier cesium beam tube test platform, the error of the optimal Cfield current does not exceed 002 mA, which verifies the correctness of the optimization results.
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    Design of L-band space based wideband low noise amplifier chip
    ZHAO Bochao, XU Hui, YIN Pan, HE Juan, ZHANG Dawei, XU Xin
    Chinese Space Science and Technology    2020, 40 (3): 19-24.   DOI: 10.16708/j.cnki.1000.758X.2020.0028
    Accepted: 04 March 2020

    Abstract196)      PDF(pc) (4040KB)(135)      
    An L-band monolithic microwave integrated circuit (MMIC) low noise amplifier (LNA) used in satellite microwave receiver was developed with 0.25μm GaAs pseudomorphic high electron mobility transistor (pHEMT) technology. The current reuse topology structure was used to achieve lower current and the precious satellite power resource was saved. The two-stage negative feedback was applied to increase stability and gain flatness, and then satellite communication quality was improved. The constant current source bias stabilized the working conditions where current was slightly influenced by the processes. The test results show that the working current is below 35mA, from 0.9GHz to 1.8GHz, the gain is higher than 33dB with gain flatness less than 0.5dB, the noise figure is below 0.6dB, and the size of the LNA chip is 2.0mm×1.3mm. The circuit can meet the requirement of high performance and miniaturization in space application.
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    A polar navigation algorithm of strapdown inertial navigation system under frozen geography frame
    CHENG Haibin, LU Hao, XU Jianyun
    Chinese Space Science and Technology    2020, 40 (2): 35-.   DOI: 10.16708/j.cnki.1000-758X.2020.0017
    Abstract194)      PDF(pc) (3882KB)(80)      
    Aiming at the problem that the classical mechanizations of inertial navigation system in polar region are unable to confirm its position and heading, a new polar navigation scheme based on frozen geography frame was proposed, which is suitable for strapdown inertial navigation system. This scheme uses threeaxis position instead of longitude, latitude and altitude for navigation in polar region. This algorithm has no singularity in navigation calculation. The mechanizations under the frozen geography frame were given. The parameter transformations from a frozen geography frame to geography frame for position, velocity and attitude were deduced. The simulation and analysis results show that this method can solve the problem that the north benchmark is invalid, and that the navigation parameters are continuous and have no theoretical errors. The mechanizations under the frozen geography frame can meet the requirement of  transpolar aircraft.
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    System design and key technolongies of the GF-7 satellite
    CAO Haiyi, ZHANG Xinwei, ZHAO Chenguang, XU Chi, MO Fan, DAI Jun
    Chinese Space Science and Technology    2020, 40 (5): 1-9.   DOI: 10.16708/j.cnki.1000-758X.2020.0052
    Abstract191)      PDF(pc) (5941KB)(152)      
    GF-7 satellite is the first 1∶10000 scale stereoscopic surveying and mapping satellite independently developed in China, and an important part of the national high resolution earth observation system. The satellite is based on the active and passive combined surveying and mapping system of “two-line array surveying and mapping + laser altimetry” and forms a series of key technologies and innovation points, such as highprecision internal/external element stability design, highprecision attitude stability control, the first X-band adaptive high-rate data transmission system, and onboard intelligent satellite management system. The capability of large scale stereoscopic mapping with little or no control points was realized. The system design of the satellite was described, and the technical innovation points were summarized such as observation system, high-precision load, attitude control, digital data transmission, intelligent satellite service, etc. The preliminary evaluation was carried out through the test results of satellites in orbit, and the satellites can meet the requirements of the 1∶10000 surveying and mapping mission.
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