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25 April 2020, Volume 40 Issue 2 Previous Issue    Next Issue

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A high accuracy pointing control method for space target FENG Tiantian, GAO Jingmin 2020, 40 (2):  1.  doi: 10.16708/j.cnki.1000-758X.2020.0013 Abstract ( 588 )   PDF (3717KB) ( 478 )   Save 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. Related Articles | Metrics

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Optimal design of droplet layer in liquid droplet radiator ZHAO Xingying, LI Qiang 2020, 40 (2):  10.  doi: 10.16708/j.cnki.1000-758X.2020.0014 Abstract ( 349 )   PDF (3701KB) ( 256 )   Save To improve the radiation heat flux in the droplet layer of liquid droplet radiator, a 3D unsteady radiation heat transfer model of the rectangular droplet radiator was established. The radiation heat transfer process of droplet layer was simulated by FLUENT. The influence and sensitivity of droplet distribution characteristics, initial droplet temperature, flow rate, droplet spacing, diameter, droplet length and mass flow rate on the radiation heat flux of droplet layer were analyzed numerically. A new droplet layer structure,hollow droplet layer，was proposed. Results show that apart from flight time and mass flow rate, droplet spacing and initial temperature have great influence on the heat transfer power of the droplet layer of radiator. Under the condition that the number of droplet layers in the thickness direction is 100 and the mass flow rate is 12 kg/s, the design of hollow droplet layer can increase the heat flux per unit mass by 23 times. Related Articles | Metrics

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Multi satellite imaging planning method with optimal response time for emergency tasks CHEN Shujian, LI Zhi, HU Min, ZHANG Yasheng 2020, 40 (2):  17.  doi: 10.16708/j.cnki.1000-758X.2020.0015 Abstract ( 430 )   PDF (8393KB) ( 173 )   Save The problem of response time in multisatellite imaging planning for emergency tasks was investigated. To avoid the influence of preferentially planning of emergency tasks on total task revenue, a multisatellite imaging planning method was proposed, with which the response time of emergency tasks was optimized and the total task revenue was considered. Firstly, according to the characteristics of multisatellite imaging planning which considers both emergency and routine tasks, a constraint satisfaction model for twolevel target optimization was established. Secondly, the model solving process was divided into two parts,i.e., selection of time window and dynamic planning on single orbit. The selection of time window was optimized based on adaptive immune algorithm, and the forward dynamic planning algorithm was designed to determine the optimal path of satellite on single orbit. Finally, the designed algorithm was tested and compared with other algorithms. Simulation results demonstrate that the proposed method can ensure the shortest response time of emergency tasks and get relatively high total task revenue in largescale problem of multisatellite imaging planning. Related Articles | Metrics

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A guidance algorithm for midcorrection of translunar trajectory BEN Liyan, ZHANG Rui, XIE Xianghua 2020, 40 (2):  29.  doi: 10.16708/j.cnki.1000-758X.2020.0016 Abstract ( 316 )   PDF (1220KB) ( 282 )   Save A new guidance algorithm for midcorrection of translunar trajectory was presented. The algorithm was divided into two steps, i.e.,designing the initial solution and searching for the exact solution. First, the initial solution was generated using the pseudostate theory, and the Vinti prediction was adopted to improve the accuracy of the initial solution by eliminating the earth oblateness effect. Then, while searching for the exact solution, the state transition matrix was calculated by an analytical method based on the pseudostate theory. Because the initial solution with high accuracy is used, the difficulty of finding the solution for midcorrection of translunar trajectory is greatly reduced. Moreover, the calculation of the state transition matrix by using traditional numerical methods is omitted. Numerical simulations indicate that the algorithm is of high efficiency. Related Articles | Metrics

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A polar navigation algorithm of strapdown inertial navigation system under frozen geography frame CHENG Haibin, LU Hao, XU Jianyun 2020, 40 (2):  35.  doi: 10.16708/j.cnki.1000-758X.2020.0017 Abstract ( 482 )   PDF (3882KB) ( 235 )   Save 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. Related Articles | Metrics

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All electric propulsion satellite trajectory optimization by homotopic approach DUAN Chuanhui, REN Lixin, CHANG Yajie, BAI Qian, AN Ran, HUANG Yusong 2020, 40 (2):  42.  doi: 10.16708/j.cnki.1000-758X.2020.0018 Abstract ( 622 )   PDF (2941KB) ( 599 )   Save The orbit injection of allelectric propulsion satellite is a typical low thrust multirevolution orbit optimal problem. Due to the small acceleration and the large number of revolutions, it is difficult to solve the optimal theoretical solution. In order to solve this problem, the indirect method model of allelectric propulsion satellite orbit optimization was established by using the optimal control theory, and the problem of the orbital optimization was transformed into the twopoint boundary value problem which can be solved by guessing the initial costate variable. A large thrust problem was solved by combining the evolutionary algorithm and the sequential quadratic programming. With the help of homotopic approach, the small thrust problem was solved by gradually reducing the thrust. The simulation shows that the thrust homotopic method can effectively solve the trajectory optimal of geostationary allelectric propulsion satellites with up to hundreds of revolutions by dozens of thrust reductions. Related Articles | Metrics

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Analysis method of electromagnetic compatibility for radiofrequency system between human spacecraft and adjoint satellite SUN Ben, WANG Wei, LIANG Ke, XU Xiaoguang 2020, 40 (2):  49.  doi: 10.16708/j.cnki.1000-758X.2020.0019 Abstract ( 370 )   PDF (859KB) ( 308 )   Save The electromagnetic interference(EMI) of radiofrequency(RF) equipments between human spacecraft and adjoint satellite was investigated. Based on the design of RF equipments, the model of calculating safety margin was built and the equivalent interference between transmitting antenna and receiving antenna was analyzed. To guarantee the electromegnetic compatibility, the minimal safe distance of two spacecrafts was obtained. The results show that the approach proposed in the paper can forecast the electromagnetic interference between human spacecraft and adjoint satellite, and provide technical support for the fulfillment of the mission. Related Articles | Metrics

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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 2020, 40 (2):  54.  doi: 10.16708/j.cnki.1000-758X.2020.0020 Abstract ( 471 )   PDF (3810KB) ( 262 )   Save 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. Related Articles | Metrics

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Simulation analysis of the influence of quality characteristics on spacecraft pyroshock transmission YANG Guang, LIU Bo, LI Zhengju, DENG Mingle 2020, 40 (2):  62.  doi: 10.16708/j.cnki.1000-758X.2020.0021 Abstract ( 443 )   PDF (7866KB) ( 76 )   Save Pryoshock environment on the spacecraft is complex, the impact load is transient and highly nonlinear， which makes the pyroshock response difficult to be predicted. Quality characteristics of equipment distributing on satellite boards become the key factor of pyroshock transmission. According to the mechanism of pyroshock transmission, the simplified finite element method (FEM) models of satellite boards and equipment were built and the responses on the satellite boards were calculated. Comparing the results with test data, the error was controlled under ±35dB which confirmed the rationality of the FEM modeling. The method of simulation provides a reference for the prediction of pyroshock response and the design of satellite layout. Related Articles | Metrics

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Application of multivariate global optimization and intelligent optimization in constellation design LI Zhiwu, HE Yanchao, LYU Qiujie, ZHANG Lei, ZHU Zhengfan 2020, 40 (2):  70.  doi: 10.16708/j.cnki.1000-758X.2020.0022 Abstract ( 430 )   PDF (3042KB) ( 305 )   Save Top mission design is usually closely associated with satellite constellation. The decentralized and flexible features of small satellites match the use of largescale constellation in orbit. The application method of multivariate global optimization and intelligent optimization for constellation design was presented with consideration for the different mission requirements of hotspot coverage and global coverage. Therefore, the optimal performance of small constellation and the superior performance of largescale constellation could be obtained. These methods for satellite constellation optimization are not restricted by orbit types and mission target distributions, and show the good performance of robustness. Related Articles | Metrics

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A timecalibration method with controllable second interrupt interval for onboard computers ZHANG Cuitao, WANG Luyuan, GUO Jian, HE Xiongwen 2020, 40 (2):  76.  doi: 10.16708/j.cnki.1000-758X.2020.0023 Abstract ( 423 )   PDF (997KB) ( 200 )   Save The traditional onboard computer time maintenance is mainly implemented by software. In order to avoid the second interrupt interval being too small or too large during the time calibration process, the software needs to perform multiple operations on the external timer Intel 82C54 chip through complicated logic and algorithms. It is very likely to make mistakes, and it takes a lot of CPU machine cycles. With the increasing tasks for spacecraft intelligent processing in the future, the CPU machine cycle becomes more and more scarce. In order to free the CPU from the cumbersome time calibration operation, a timecalibration method with controllable second interrupt interval based on FPGA was proposed. The satellite time timer was designed with the FPGA logic circuit. And the trigger condition of timecalibration was designed by using the constraint condition of second interrupt interval. When the trigger condition of timecalibration is met, the FPGA logic circuit automatically executes the timecalibration operation, which solves the problem of too large or too small second interrupt intervals during the timecalibration process, and saves a lot of CPU machine cycles. The timecalibration method proposed has been applied on several onboard computers, and has achieved the expected goal. Related Articles | Metrics

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Design of expandable diffuser board on GF5 VIMI JIN Libing, WANG Hao, ZHAO Yanhua, HU Bin, SHI Dongliang, Lian Minlong 2020, 40 (2):  81.  doi: 10.16708/j.cnki.1000-758X.2020.0024 Abstract ( 430 )   PDF (4375KB) ( 228 )   Save For the longterm monitoring and correcting of the radiometric performance of the imager, the expandable diffuser used for calibration in full FOV and full optical path method was designed, considering the characteristics and requirements of its wide spectrum range, high accuracy requirements, large aperture and long service life.The solar diffuser is installed on the front side of the optical system and does not affect the normal imaging of VIMI.When VIMI needs calibration，the diffuser is expanded to the front of the optical system via the driving mechanism. According to the characteristics of the GF5 satellite orbit, the requirement of the calibration energy and the installation matrix of the imager relative to the satellite, the expansion angle of the diffuser is 39°. The 430mm×430mm largesize PTEE diffuser is manufactured to ensure full FOV and full optical path calibration. The diffuser’s directional hemispherical reflectance is higher than 95% when the spectrum ranges from 420nm to 2400nm， and variation of  BRDF in the direction of imager observation is better than 25%.The diffuser stability monitoring radiometer is designed to monitor the onorbit attenuation performance of the diffuser, and the monitoring accuracy is 15%. The accuracy of onorbit calibration is 476%, which meets the requirement of index. Related Articles | Metrics