Dec 2021, Volume 8 Issue 6
    

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  • Topic：Lunar and planetary TT&C Technology
    Review on Development History of TT&C System of China's Lunar and Planetary Exploration Projects
    YU Zhijian, LI Haitao
    2021, 8(6): 543-554. https://doi.org/10.15982/j.issn.2096-9287.2021.20210125
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    In this paper，the author gives a comprehensive review of the achievements made by China in the construction of deep space TT&C system，combining with the development of the TT&C system from near earth to deep space during the 17 years since the successful implementation of the three-step strategy of “circling，landing and returning” of China’s lunar exploration project. From the breakthrough of long-distance TT&C technology in the first phase of the lunar exploration project，to the initial completion of the deep space TT&C network of two domestic deep space stations in the second phase of the lunar exploration project，to the completion of the Deep space station in Argentina in the third phase of the lunar exploration project，a complete deep space TT&C capability was formed. Today，China’s deep space TT&C system has become one of the three global deep space TT&C networks in the world，and is capable of independently supporting lunar and deep space exploration missions. In the future，China’s deep space TT&C system will continue to develop and grow in accordance with the principle of unified planning and step-by-step construction，which will further enhance China’s support capacity for deep space TT&C.
  • Topic：Lunar and planetary TT&C Technology
    A Control Method of Sleep-Reboot in the Complex Lunar Far-Side Environment of Yutu-2
    ZHANG Kuan, LU Hao, LI Lichun, YU Tianyi, ZHANG Hui, XIE Jianfeng
    2021, 8(6): 555-563. https://doi.org/10.15982/j.issn.2096-9287.2021.20210054
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    A control method of sleep-reboot in complex lunar far-side environment is proposed in this paper for solving Yutu-2 lunar rover sleep-reboot control problem under contraints conditions of complex terrain and relay communication. A skyline sensing method based on the sequence imaging of the monocular camera is proposed to realize the occlusion analysis，a lunar attitude prediction method is proposed to realize the calculation of sleepable attitude and control strategy for a given location，a sleepability analysis index and a visualization comprehensive analysis method are proposed to assist in finding alternative sleep locations. Finally，the implementation mode of sleep-reboot on-orbit is designed and presented. The Yutu-2 on-orbit implementation performance proves the validity of the control method and the effectiveness of the process.
  • Topic：Lunar and planetary TT&C Technology
    Path Planning of Lunar Surface Sampling Manipulator for Chang'E-5 Mission
    HU Xiaodong, ZHANG Kuan, XIE Yuan, ZHANG Hui, LU Hao, LIU Chuankai, CHEN Xiang, ZHAO Huanzhou, XIE Jianfeng
    2021, 8(6): 564-571. https://doi.org/10.15982/j.issn.2096-9287.2021.20210095
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    Aiming at the problem of precise control of the sampling manipulator in the lunar surface sampling mission of "Chang'E-5"，a path planning method based on deep reinforcement learning is proposed. By designing the multi-constraint reward function of the deep reinforcement learning algorithm，a motion path that satisfies the three constraints of safety，speed and reachability is planned. The precise control of the sampling robotic arm is realized. Under the advance of meeting the task safety，the interaction time between heaven and earth is greatly shortened，and the control effect of the manipulator is more stable. Experimental results show that this method has high accuracy and robustness，and can provide reference for subsequent on orbit sampling tasks.
  • Topic：Lunar and planetary TT&C Technology
    Perfermance Analysis of Deep-Space Interferometry in Chang'E-5 Mission
    REN Tianpeng, LU Weitao, KONG Jing, XIE Jianfeng, HAN Songtao, WANG Mei, MAN Haijun, NIU Dongwen, LIU Heshan, ZHOU Zhijin
    2021, 8(6): 572-581. https://doi.org/10.15982/j.issn.2096-9287.2021.20210055
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    China’s deep space interferometry system has participated in orbit measurement for the Chang’E-5 mission officially, which has provided high-precision angular position information. The tropospheric delay hybrid model was proposed to ensure the accuracy of real-time interferometry. Using the non-continuous tracking technology, fast intercontinental interferometry was carried out for the first time, which provided high-precision angular position with the advantage of baseline length. The performance was evaluated based on the orbit measurement results of Chang’E-5 probe. These results show that the deep-space interferometry system has played an important role in the fast orbit determination.
  • Topic：Lunar and planetary TT&C Technology
    Teleoperation Technology of Zhurong Mars Rover
    ZHANG Hui, LU Hao, YU Tianyi, XIE Yuan, WANG Cheng, BAO Shuo, HU Xiaodong
    2021, 8(6): 582-591. https://doi.org/10.15982/j.issn.2096-9287.2021.20210108
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    Restricted by the delay of TT&C communication link，communication bandwidth and relay communication arc，interplanetary space teleoperation technology is different from Earth Moon space teleoperation technology. The mission characteristics，technical difficulties and flight control design constraints of the Mars rover teleoperation are summarized. Aiming at solving the technical problems of the first interplanetary space teleoperation of China，this paper studied and established the Mars rover teleoperation control mode and key technology system，put forward the overall design method and system architecture of the Mars rover Teleoperation system，and designed the Mars rover teleoperation flight control mode and implementation process. The method proposed in this paper has been successfully applied to the teleoperation mission of Zhurong Mars rover. Zhurong Mars rover always maintains efficient movement and exploration，and the 100 d teleoperation mileage exceeds 1 kilometer，which verifies the correctness and effectiveness of this method，and lays a technical foundation for follow-up interplanetary space teleoperation missions.
  • Topic：Lunar and planetary TT&C Technology
    Analysis of Delay Error Correction of Solar Plasma Region on Tianwen-1
    DUAN Chenglin, ZHANG Yu, HAN Yi, DUAN Jianfeng
    2021, 8(6): 592-599. https://doi.org/10.15982/j.issn.2096-9287.2021.20210103
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    When electromagnetic wave flies through the interplanetary space region，the solar plasma will bring large reflection loss to the TT&C communication signal and reduce the power of the TT&C communication signal. The influence of time delay error of electromagnetic wave on ranging can reach tens of meters in one way. In this paper，the formation principle of the solar plasma region was analyzed，the relationship between the plasma delay error and the angle of Sun-Earth-Probe（ SEP ）and the distance r between the detector and the sun center was simulated，and the influence of the solar plasma time delay of Tianwen-1 on ranging was discussed. The results show that the plasma delay decreases with the increase of the SEP and r ，and the effect of solar plasma delay on ranging is less than 2 m due to the SEP more than 20° in the Earth-Mars transfer orbit and the initial orbit of the circum-Mars，while the two-way effect of solar plasma time delay on ranging increases gradually from about 2 ～ 100 m when the SEP is less than 20° and close to 0°. The delay effect of solar plasma must be considered in precise orbit determination. After plasma delay error correction of ranging data，the residual error can be eliminated by dynamic orbit improvement，and the final residual error of orbit determination can reach within 4 m.
  • Topic：Lunar and planetary TT&C Technology
    Design of Multi-Station Frequency Transfer System for VLBI Deep Space TT&C Based on Single Fiber
    CHANG Jie, WANG Jinqing, SHU Fengchun, JIANG Yongchen
    2021, 8(6): 600-607. https://doi.org/10.15982/j.issn.2096-9287.2021.20210057
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    Very Long Baseline Interferometry （VLBI） technology requires a stable frequency datum for high-precision angular measurement in lunar and planetary explorations. A multi-user frequency transfer system for VLBI stations using only single optical fiber is designed. It realizes full-automatic fast round-trip correction phase loop without PLLs， using mixer and circulator to deliver stable standard frequency signal to antennas. The system has both real-time compensation mode and post compensation mode，and supports multiple receivers to meet the needs of VLBI stations with multiple radio telescopes. The practical results show that the frequency stability reach 10?17/day level within the ability to the 10?19 in real-time compensation mode and 10?18/day in post compensation mode. VLBI observation for radio source and HX-1 shows that the clock rate difference is reduced to 10?14 level， which can effectively reduce errors. The requirements that multiple antennas share the same oscillator has been fulfilled. At present， the system has been applied in VLBI deep space TT&C and EOP observation, maintaining high reliability.
  • Topic：Lunar and planetary TT&C Technology
    A Backtracking Method Based on Frame Synchronization for Deep Space Super Low Bit Rate Data
    CHEN Shaowu, LIU Min, WANG Jinwen, QIANG Li, LU Ouxin
    2021, 8(6): 608-613. https://doi.org/10.15982/j.issn.2096-9287.2021.20210122
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    Due to the super low telemetry bit rate and limited transmitting time for deep space mission，the total received telemetry data is precious; it is necessary to obtain as much telemetry data as possible，and decrease overhead and increase the efficiency of data receiving. A backtracking method（BTM）for deep space super low bit rate frame synchronization data was proposed in this paper for the data loss in the process of three-state transfer in traditional frame synchronization. The data frames in the process of three-state transfer in frame synchronization were backtracked，and multiple valid telemetry data frames were obtained by using the valid frame synchronization information. The method was successfully applied to the super low telemetry data receiving for orbiter and rover in Tianwen-1 Mars exploration mission. The result shows that 2~4 more valid data frames were obtained with the method proposed compared with the traditional method，and transfer efficiency was improved by 13%~40%. More valid data frames and higher transfer efficiency could be obtained by using the method. The method proposed in this paper can be particularly useful for deep space super low bit rate telemetry data receiving，and could be used in the further exploration of asteroids，Jupiter and the boundary of the solar system.
  • Article
    Research on Spatial Distribution Characteristics of Lunar from Possible Sunshine Duration Spectrum and Solar Radiation Spectrum
    LIU Qiqi, CHEN Nan, LIN Siwei
    2021, 8(6): 614-624. https://doi.org/10.15982/j.issn.2096-9287.2021.20210100
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    The paper use the lunar DEM with 20m resolution as the data source，16 typical lunar areas in different latitudes were selected. Then，we build a parallel computing framework to conduct numerical simulations of PSD and SR on each experimental sample area in 2020. Then，utilizing the slope spectrum model on digital terrain analysis，we use the rectangular window expansion method to define the PSD spectrum and SR spectrum. On this basis， the slope-mean PSD spectrum in a year，slope-mean SR spectrum in a year and aspect-mean SR spectrum in a year were derived. Meanwhile，the stable area values of different spectrums were extracted. The results show that： It can be seen that the spatial distribution of PSD and SR is significantly affected by terrain ；On the whole，with the increase of latitude，the solar altitude angle decreases，the terrain shielding effect becomes more obvious，resulting in the decrease of PSD spectrum and SR spectrum；The stable area value of the slope-mean possible sunshine duration spectrum on sample areas is positively correlated with the variation coefficient of slope. The result can be employed as a import support for the construction of the lunar base in the future.
  • Article
    Initial Trajectory Design of the Electric Sail Escaping from Solar System Based on the Bezier Curve Method
    FAN Zichen, HUO Mingying, REN Hui, QI Naiming
    2021, 8(6): 625-631. https://doi.org/10.15982/j.issn.2096-9287.2021.20200088
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    The detection of the solar system boundary has gradually attracted people's attention. To explore the solar system boundary，we need to find an efficient propulsion system and design a reasonable trajectory to escape from the solar system. Therefore，this paper proposes to use the Bezier shape-based method to quickly generate the three-dimensional trajectory of the electric sail escaping from the solar system，which provides an appropriate initial solution for a more accurate trajectory optimization algorithm. By taking the results obtained by the Bezier shape-based method as the initial solution of Gauss pseudospectral method（GPM），the applicability of the results obtained by the Bezier shape-based method to the initial solution of the direct solver is evaluated. The simulation results show that the Bezier shape-based method can design a reasonable three-dimensional initial trajectory of the electric sail escaping from the solar system for the direct optimization solver in a short time. This is of great significance for the rapid evaluation of a large number of electric sail flight scenarios in the preliminary mission design stage.
  • Article
    X-Ray Pulsar Navigation Based on Hybrid Velocimetry Method
    WU Daliang, WU Jin, LIU Jin, NING Xiaolin, KANG Zhiwei
    2021, 8(6): 632-640. https://doi.org/10.15982/j.issn.2096-9287.2021.20210114
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    In order to suppress the Doppler effects in pulsar signals caused by spacecraft velocity，a novel method of X-ray pulsar navigation based on direct/indirect hybrid velocimetry was proposed. The direct velocimetry method provided velocity information directly according to the distorted pulsar profile. It had high accuracy，but was only suitable for high flux pulsar，namely Crab pulsar. A distorted profile matching estimation method for direct velocity and distance measurement was proposed. The indirect velocimetry method was to establish the relationship model between velocity and pulsar time-of-arrival，and provide velocity information by Kalman filter indirectly. The signal-to-noise ratio of low flux pulsar distortion profile was very low，which could not reflect the weak pulsar distortion. Therefore，the indirect velocimetry method was suitable for low flux pulsars. Based on this，the direct velocimetry method and the indirect one were used to update the Kalman filter in turn. And the Kalman filter was used to provide high-accuracy navigation information. Simulation results show that the accuracy of X-ray pulsar navigation method based on direct/indirect hybrid velocimetry is 15% higher than that of the indirect pulsar navigation.