May 2022, Volume 7 Issue 2
    

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  • Review
    Preliminary Study on Key Technologies for Construction and Operation of Robotics Lunar Scientific Base
    YANG Jianzhong, WU Qiong, YU Dengyun, JIANG Shengyuan, XU Zhaodong, CUI Pingyuan
    2020, 7(2): 111-117. https://doi.org/10.15982/j.issn.2095-7777.2020.20190509001
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    Robotics lunar scientific base is of great significance to the deep exploration and exploitation of lunar resources. It is one of the strategic targets of space science and technology for space powers，and the key technologies in the construction and operation are primary problems to be solved in the lunar base project. A basic sketch of robotics lunar scientific base is given，and main technical problems for construction and operation of the base are also pointed out. Key technologies should be broken through are then proposed，including active soft-landing design，soft-landing safety boundary identification，adaptive gait planning，comprehensive lunar environmental damage equivalent，service life prediction and control，etc. Finally，recommendations for the implementation of the base are proposed，providing reference for the research and construction of the future robotics lunar scientific base of China.
  • Review
    Key Technologies for Space Science Gravitational Wave Detection
    WU Shufan, WANG Nan, GONG Deren
    2020, 7(2): 118-127. https://doi.org/10.15982/j.issn.2095-7777.2020.20190402001
    The concept of gravitational waves is first introduced，describing the causes of gravitational waves. Typical science missions of ground and space gravitational wave detections are summarized，elaborating their major differences. Then the key technologies for space science gravitational wave detection are investigated，and its future development trends are analyzed. Finally，it is pointed out that the implementation of the gravitational wave detection task will also play an active role in the fields of inertial navigation，earth science，high-precision satellite platform construction and other applications，and it is of great significance to improve the technical level of space science and deep space exploration in China.
  • Topic: FAST Application Goal and Associated Technology
    Introduction to Main Application Goals of Five-hundred-meter Aperture Spherical radio Telescope
    YAN Jun, ZHANG Haiyan
    2020, 7(2): 128-135. https://doi.org/10.15982/j.issn.2095-7777.2020.20190618003
    The main structure of Five-hundred-meter Aperture Spherical radio Telescope（FAST）has been completed. Till now, more than 100 new pulsars have been detected by FAST during the commissioning and test observation stage, and the project passed the national review in January 2020. Being the largest and most sensitive single-dish radio telescope, FAST will enable scientists to jump-start many science cases. Meanwhile, FAST have several application goals described in this paper. For instance, in deep space exploration, FAST will improve the ability of space measurement and control to the edge of the Solar System. Moreover, FAST will increase the measurement accuracy of the time of arrival for the pulsar to 30 ns and develop the most accurate pulsar timing array, which will work for autonomous navigation. FAST could be the receiving system of the incoherent scattering radar, providing the ground-based observation with high resolution and efficiency. By carrying out microware survey to detect weak space signals, FAST might work for the Search for Extra Terrestrial Intelligence（SETI）and national security. After the formal operation, FAST will make significant contributions to these important application goals.
  • Topic: FAST Application Goal and Associated Technology
    VLBI System and Scientific Research of FAST
    CHEN Rurong, ZHANG Haiyan, JIN Chengjin, GAO Zhisheng, ZHU Yan, YUE Youling, ZHU Kai
    2020, 7(2): 136-143. https://doi.org/10.15982/j.issn.2095-7777.2020.20190618001
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    As the biggest single dish radio telescope in the world, FAST would significantly improve the capability of current VLBI networks below 3 GHz. There are several VLBI networks, such as CVN, EVN and LBA, are suitable for FAST to join, after considering the location of stations and frequency of receivers. FAST would mainly contribute sensitive long baselines to the current VLBI networks, which would benefit the research in need of high resolution and high sensitivity. The slewing speed of FAST is not high. In order to effectively join the phase-referencing observations, selection of nearby calibrator or a new small antenna could be the solution.Very Long Baseline Interference (VLBI) is one of the topic sciences of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), which would provide significant contribution to the current VLBI networks. In order to make use of the significant contribution of FAST to the VLBI observations, it is necessary to pick suitable VLBI research projects. We summarize their main VLBI projects of three mega radio telescopes with hundred-meter aperture and give some suitable VLBI projects for FAST. FAST VLBI system consists of time/frequency system, the data sampling terminal and the data reservation system, which are all state of the art. Two fringe experiments were conducted and the first VLBI fringe between FAST and Tianma telescope was introduced. Future plans, including suitable VLBI networks to join, are discussed. Six suitable VLBI research projects are selected for FAST. The first VLBI fringe was achieved between FAST and Tianma telescope. VLBI networks, such as CVN, EVN, and LBA are suitable for FAST to contribute its significant sensitivity. Nearby small antenna could help FAST to join the phase referencing observations.
  • Topic: FAST Application Goal and Associated Technology
    Study on Electromagnetic Compatibility Between FAST and Mobile Base Stations
    HUANG Shijie, ZHANG Haiyan, HU Hao
    2020, 7(2): 144-151. https://doi.org/10.15982/j.issn.2095-7777.2020.20190618004
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    Radio telescopes are vulnerable to the Earth’s artificial electromagnetic signal interference. In order to protect the electromagnetic environment of Five-hundred-meter Aperture Spherical radio Telescope (FAST), the mobile base station interference detection experiment was carried out. By compatibility analyzing the electromagnetic of single and multiple base stations and FAST, and combining the propagation loss around the telescope, the measures to reduce the interference of base stations and ensure the communication demand of surrounding residents are studied, providing useful suggestions for reducing the interference of base stations.
  • Topic: FAST Application Goal and Associated Technology
    Protection Measures of FAST Radio Environment
    HU Hao, ZHANG Haiyan, HUANG Shijie
    2020, 7(2): 152-157. https://doi.org/10.15982/j.issn.2095-7777.2020.20190618002
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    The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is located in the remote area of Qiannan prefecture in Guizhou province. The largest single dish radio telescope in the world is build in the karst depression. Since FAST observes very weak electromagnetic signals from distant celestial sources in the Universe with extremely high sensitivity, it is easy for FAST to receive electromagnetic interference from the telescope’s own equipments and the surrounding site. The electromagnetic interference level around the site is required to be extremely low. In order to achieve the objective of scientific observation, an important basic condition for FAST is how to keep the quiet electromagnetic environment around the telescope. Several main measures have been studied. At first, in order to protect FAST quiet electromagnetic environment, the first step to reduce the radio interference is to set up a radio quiet zone within a radius of 30 km with FAST site as the center. Secondly, the strict Electromagnetic Compatibility requirements of telescope itself and its surrounding electronic and electrical equipments are required to prevent interferences from the telescope. Based on the effective electromagnetic compatibility design and protection measures, the radio environment of FAST station is quiet and stable. Due to the economic development in Guizhou province, especially in Qiannan prefecture, the number of construction projects around FAST site has increased rapidly. In the face of the coordination with many radio communication services and local economic projects, how to achieve a balance between the scientific needs and local development is the key subject for the maintenance of FAST radio quiet zone.
  • Topic: FAST Application Goal and Associated Technology
    Commensal Observation of SETI at FAST
    ZHANG Zhisong, ZHANG Haiyan, ZHU Yan, JIN Chengjin, ZHANG Tongjie, LI Di, ZHU Lichun
    2020, 7(2): 158-163. https://doi.org/10.15982/j.issn.2095-7777.2020.20190618005
    Search for Extra Terrestrial Intelligence (SETI) is an important subdomains in radio astronomy. In order to obtain as much observation time as possible, SETI adopts the Commensal Survey which does not occupy the telescope's time alone, searching for SETI signals while the telescope performs other observation tasks. In this paper, the concept of SETI commensal observation and the overall framework of SETI backend are introduce, and the main strategies of SETI commensal observation are analyzed. The real-time data receiving system SERENDIP ia analyzed and explained. At the same time, radio frequency interference (RFI) removal and candidate target extraction methods are analyzed. The validity of SETI backend is verified by processing FAST's 5-hour drift scan data. Finally, the future development trend of SETI is prospected. The high sensitivity of the 500 meter aperture spherical telescope (FAST) makes this project not only an effective verification of other telescope observation data, but also increases the possibility of detecting weak extraterrestrial signals.
  • Article
    Design of Handheld Corer for Lunar Regolith Based on Particle Directional Flow Method
    CHEN Huazhi, LIU Rongkai, MA Chao, JIANG Shengyuan
    2020, 7(2): 164-170. https://doi.org/10.15982/j.issn.2095-7777.2020.20171124001
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    Obtaining lunar regolith with primary bedding information is one of the important targets in lunar-landing and manual sampling mission. A large resistance and low coring ratio will appear when using a conventional penetration-type corer to get lunar regolith. An efficient solution is to discharge the lunar regolith particles that contact the coring pipe. The particles can flow directionally on an asymmetric friction surface under vibration. Based on this method, a designing scheme of a handheld corer for astronaut is proposed. The pivotal component structures are designed and analyzed in detail. The coring performance is studied by using the numerical simulation software EDEM based on the discrete element method. The result indicates that the corer can increase the coring ratio and reduce the resistance observably, compared with the penetration-type corer.
  • Article
    Simulation Analysis of Dynamic Behavior of Lander Footpad Impact on Lunar Regolith
    LIN Yuncheng, LI Liben, ZHAO Zhenjia, ZHANG Rongrong, JIN Cong, ZOU Meng
    2020, 7(2): 171-177. https://doi.org/10.15982/j.issn.2095-7777.2020.20190313002
    It is important to study the interaction between lander footpad and lunar regolith for landing stability, safety and landing mechanism design. In this paper, a dynamic mechanical model of lunar regolith impacted by footpads with angle is built, and the dynamic changes of lunar soil under 0°、8°、15°、22° impact angle and 1 m/s, 2 m/s and 4 m/s impact velocity are analyzed by Discrete Element Method (DEM). It is concluded that the maximum impact force is 5080.6 N when the impact velocity is 4 m/s and the impact angle is 0°, and the impact angle was larger; the impact force is smaller when the vertical displacement is the same. In addition, the bigger the angle of footpad impact on lunar soil, the smaller the compaction effect on lunar soil. The change of porosity before and after 22° is only 26.5 %. When the impact angle is fixed, the higher the velocity, the more compact the lunar soil is, and the greater degree of compaction. When the impact velocity is 4 m/s, the change of porosity before and after the impact is 78.1%. The research has certain reference significance for the design of landing mechanism and landing control.
  • Article
    Research About Strategies of Mars Probe Capture
    WANG Liangyue, GUO Yanning, MA Guangfu
    2020, 7(2): 178-183. https://doi.org/10.15982/j.issn.2095-7777.2020.20171123001
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    Aiming at the Mars probe capture，the three direct capture strategies，including fixed、constant and tangential angular velocity starategies are compared and analyzed through dynamic modeling and numerical simulation of typical conditions. The merits and demerits of three strategies are summarized，and the results show that the tangential angular velocity strategy uses low fuel，but needs real-time velocity. Also，it discovers that the optimal ignition time point corresponds to the half of total capture time. In order to implement specific transition track，a closed-loop guidance strategy is proposed based on the Zero Effort Miss/Zero Effort Velocity. Comparing with the tangential angular velocity strategy，the proposed strategy achieves equivalent effort and can satisfy terminal position and velocity constrains. It can provide an alternative strategy for the practical mission.
  • Article
    Research on Optimal Deorbit Guidance Method for Mars Exploration
    TENG Rui, HAN Hongwei, QIAO Dong
    2020, 7(2): 184-190. https://doi.org/10.15982/j.issn.2095-7777.2020.20190315001
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    The EDL phases are of great importance in Mars exploration mission，while before which the deorbit braking is a key maneuver to ensure the smooth execution of the atmospheric entry process. Aiming at the problem of deorbit maneuver before Mars entry，a burn-coast optimal deorbit guidance method is presented. Based on the local linearization of the state equation，the analytical forms of state and costate variables are obtained. The solution equations of the optimal burn-coast deorbit guidance law are given through derivation of the necessary conditions for optimal deorbit maneuver. The simulation results show that the proposed guidance strategy has good robustness on the premise of guaranteeing optimality and guidance accuracy，providing theoretical reference for the future deorbit maneuver in Mars exploration.
  • Article
    Autonomous Navigation Method for Mars Rover Using Distributed EKF-SLAM Assisted by Sun Sensor
    PEI Fujun, YAN Hong, ZHU Mingjun
    2020, 7(2): 191-196. https://doi.org/10.15982/j.issn.2095-7777.2020.20171117001
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    Since the existing SLAM algorithm can not meet the actual demand of the Mars rover autonomous navigation problem in real-time and accuracy, a distributed EKF-SLAM algorithm is proposed based on heading assistance to achieve the rover's autonomous navigation. The solar azimuth is got by using the dual axis analog sun sensor, and then the rover heading information is calculated and added it to each subsystem of SLAM. Consequently, a SLAM model of EKF-SLAM system is built and the federal EKF is adopted to realize the state estimation of the distributed SLAM system. Finally, a whole astronomical heading assistant distributed system is constructed. The experiment test is performed in outdoor experimental environment using a mobile robot, and the experimental results demonstrate the accuracy and effectiveness of the proposed algorithm.
  • Article
    Research on the Near-Earth Asteroid Observation Technology
    SUN Haibin, SUN Shengli
    2020, 7(2): 197-205. https://doi.org/10.15982/j.issn.2095-7777.2020.20180314001
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    A huge number of Near-Earth-Asteroids（NEA）pose potential threat to the security of earth. There are also large numbers of hazardous asteroids have not yet been found due to our observation technology. Aiming at the development of near Earth Asteroid space observation technology，this paper analyzes the status and level of NEAs observation technology domestic and overseas，and combining the comparison of the capabilities between the space / ground asteroid observation platform，we promote our scheme of space infrared asteroid observation based on our technology. The scheme plan to research asteroids and get its spectrum information through VIS-IR technology，through cooperative observations with space platform and ground equipment network，and then construction an integrated asteroid observation system of our country. At the same time，through the comprehensive analysis of defense strategies and utilization value of asteroids，some preliminary suggestions about the NEA’s observation，early warning，defense and other missions in china are proposed.
  • Article
    Networking Analysis of a Tetrahedral Deployable Unit Mechanism
    YANG Bin, GUO Jinwei, ZHANG Lei, HAN Bo, CHEN Liangliang, XU Yundou
    2020, 7(2): 206-212. https://doi.org/10.15982/j.issn.2095-7777.2020.20180309001
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    Facing the field of aerospace，taking the 3RR-3RRR tetrahedral deployable unit as the curved deployable antenna support mechanism，the networking method of tetrahedral unit mechanism is studied. Firstly，according to the networking principle of triangle approximating arbitrary curved surfaces，the continuous networking form and the spaced networking form are put forward and analyzed comparatively. Then，the design of curved deployable mechanism is carried out in the form of spaced networking form，and the movement process of the networking mechanism with the minimum combination unit is analyzed. Finally，the ADAMS simulation model of the minimum combination unit mechanism is established and verified. The simulation results show the correctness of the spaced networking method based on tetrahedral deployable unit. The networking method can be organized according to different sizes，forming arbitrary large curved deployable mechanisms.
  • Article
    Ultra Deep Space Exploration Mission and Power Project
    WANG Ying, ZHU Anwen, LIU Feibiao, TIAN Dai, WANG Zhu
    2020, 7(2): 213-220. https://doi.org/10.15982/j.issn.2095-7777.2020.20190327001
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    China has carried out a lot of research work in the field of deep space exploration （more than dozens of AU）but the ultra deep space exploration mission has not yet been launched. Interstellar exploration can greatly enhance the space exploration, improve the self-sufficiency of data required by space science research, and reach the international leading level in the world. Far away from Jupiter, satellites will get less solar mediation intensity, how to generate electricity and how to prevent the satellites too cold should be considered. So we need to design a reasonable energy system by considering the limit conditions about flight space environment, task life and weight. Based on the investigation of relevant tasks in foreign countries and the existing technical basis in China, the space nuclear energy system is selected as the main power solution. Meanwhile, the conceptual propulsion design is also considered, and the task assumption and key technologies to be developed are put forward.