Jan 2024, Volume 10 Issue 6
    

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  • Mission Analysis and Spacecraft Design of Chang’E-7
    YU Houman, RAO Wei, ZHANG Yiyuan, XING Zhuoyi
    2023, 10(6): 567-576. https://doi.org/10.15982/j.issn.2096-9287.2023.20230119
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    In recent years, international lunar exploration has mainly focused on the south pole of the Moon. Chang’E-7 (CE-7) mission, through the development of orbiter, lander, rover and hopper, will achieve a comprehensive exploration of the lunar south pole including surrounding, landing, moving, and leaping. The harsh lighting conditions, terrain conditions, and temperature conditions at the lunar south pole have brought many challenges to the design of the spacecraft. CE-7 spacecraft has broken through a series of barriers with advanced technologies including high-precision fixed-point soft landing on complex terrain, lunar surface leaping, lunar landing and walking, global perception and mission planning, and fidelity sampling of water ice and volatiles. It has laid a solid technical foundation for the smooth implementation of the mission and the subsequent aerospace cause in our country.
  • Comprehensive Testing Technology for Multi Spacecraft Collaboration in Chang’E-7 Lunar Probe
    FU Xiaojing, CAI Xiaodong, LIU Yiming, TIAN Guoliang, WEN Xin
    2023, 10(6): 577-585. https://doi.org/10.15982/j.issn.2096-9287.2023.20230103
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    In response to the complex joint power supply testing mode, diverse inter spacecraft and ground communication scenarios, and high requirements for simulation flight test design and verification caused by the collaboration, high complexity, high coupling, and high intelligence of Chang’E-7 lunar probe, the difficulties in system level electrical testing were analyzed, and a digital testing and verification strategy for multi vehicle collaboration was proposed. It includes a model based intelligent safety auxiliary testing for multi device joint power supply, a multi scenario high autonomous measurement and control data transmission testing system based on multi-source data autonomous decision-making, and a flight program-simulation flight test design verification system, which changes the current situation where complex system level electrical testing mainly relies on manual or traditional single satellite automated testing technology. It was applied to the development of Chang’E-7 lunar probe, to provide strong support for fully verifying the correctness, consistency, and stability of the functions and electrical performance indicators of the lunar south pole probe, achieve comprehensive, reliable, and efficient testing and verification, and promote spacecraft testing to move further from traditional automated testing of single spacecraft to collaborative intelligent testing of multiple spacecraft.
  • Terrain Reconstruction for Lunar South Pole Region Based on Confidence-Guided Stereo Matching
    YOU Qionghua, YE Zhen, TONG Xiaohua, XU Yusheng, LIU Shijie, XIE Huan
    2023, 10(6): 586-597. https://doi.org/10.15982/j.issn.2096-9287.2023.20230120
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    The lunar South Pole region’s limited illumination, extensive shadowed regions, and homogenous surface features with weak textures pose significant challenges to stereoscopic image matching and 3D terrain reconstruction. To address these issues, an Efficient Confidence-guided Stereo Matching (ECSM) algorithm was proposed. This algorithm improved matching precision and efficiency by assessing the confidence of non-support points, updating the support point dataset, constructing a triangulated mesh, and recalculating disparities within triangle vertices based on their confidence levels. On this basis, a photogrammetric method for lunar 3D terrain reconstruction was established. High-resolution image data from the Lunar Reconnaissance Orbiter’s Narrow Angle Camera was utilized for validation experiments conducted in the vicinity of the Shackleton crater within the lunar South Pole region. Qualitative and quantitative analyses of disparity maps and Digital Elevation Model (DEM) generated from different stereo matching algorithms demonstrated the reliability of the proposed algorithm in regions with weak and repetitive textures. Comparative analyses with the German Aerospace Center’s DEM and NASA’s Lunar Orbiter Laser Altimeter DEM (LDEM) for the same region revealed significant consistency in elevation and slope information, affirming the practicality and effectiveness of the proposed method. This study provides a methodological foundation for landing site selection for lunar South Pole explorations.
  • Autonomous Navigation Path Planning Algorithm for Rovers in Lunar South Pole Surface
    WANG Huiting, YU Meng, LI Yuye, HU Tao, ZHENG Bo
    2023, 10(6): 598-607. https://doi.org/10.15982/j.issn.2096-9287.2023.20230084
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    When the lunar rover in the future performs complex tasks such as shadowed regions detection and autonomous sampling and return under weak communication conditions in the lunar south pole, the demand for high-precision autonomous navigation system will become more urgent. Taking into account the safety guarantee of the lunar rover and the lunar environmental factors with navigation benefits, a new fusion path planning algorithm for high-precision autonomous navigation was proposed in this paper, by integrating a global auxiliary path based on optimized A* algorithm with Dynamic Window Approach. With location error of simultaneous localization and mapping based on lidar serving as an evaluation index, a numerical simulation and a semi physical experiment were established to verify the feasibility of this algorithm and the effectiveness of improving navigation accuracy of the rover in different application scenarios. Experiment results show that compared with traditional path planning algorithms with single factor considerations, the average absolute location error of simultaneous localization and mapping algorithm in the two-dimensional plane was reduced by a maximum of 42% when the lunar rover moved along the path planned by the proposed algorithm, which can provide technical support for autonomous navigation and path planning tasks in the complex environment of the lunar south pole.
  • Shovel Design and Testing for Micro-Quantitative Sampling of Shallow Moon Soil
    DUAN Zhangqing, ZHANG Weiwei, WANG Chu, TIAN Ye, GONG Xuejian, JIANG Shengyuan, ZHANG Yunfeng
    2023, 10(6): 608-617. https://doi.org/10.15982/j.issn.2096-9287.2023.20230118
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    In situ high-precision analyses of volatile abundance in lunar soil in the lunar polar regions require micro-quantification of test samples. In this paper, a sampling shovel scheme based on the end of a robotic arm was proposed. A shallow lunar soil profile was constructed by progressive shovel digging, micro-quantitative collection of lunar soil samples at fixed depths was achieved through the configuration of a fixed-capacity sampling chamber, and the shovel teeth could be used to scrape the debris formed by the water ice of the lunar soil for sample collection in extreme cases. To verify the feasibility of the sampling scheme, a simulated lunar soil profile shovel-digging sampling efficiency test platform was built, and progressive shovel-digging, fixed-capacity micro-sampling, and vibratory sampling tests were carried out. These tests show that the sampling shovel has the capability of constructing a 130 mm deep profile and a 200 ± 30 mg micro-quantitative sampling function. The research results provide a feasible scheme for the exploration and analysis of China’s lunar soil sampling in the polar regions of the Moon.
  • Design for In-Situ Water Ice Analysis in the Lunar Polar Region
    LI Xiang, WANG Xingping, LU Wenzhen, GUO Meiru, HUANG Zhengxu, ZHANG Xiaoping, XU Zhenyu, YAO Lu, RUAN Jun, KAN Ruifeng, CAO Nailiang
    2023, 10(6): 618-630. https://doi.org/10.15982/j.issn.2096-9287.2023.20230106
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    It is crucial to directly confirm the presence of water by detecting water ice and its content in the lunar polar region in situ. Spectroscopy and mass spectrometry are both important tools for identifying and quantifying material composition. They can complement each other to achieve comprehensive detection of water ice, volatile content, and H isotope abundance in the lunar polar region. The paper introduces the spectroscopy and mass spectrometry technique with Luna 25, Luna 27 and Viper as examples of typical in-situ detection applications. It includes the detection mechanism, operating mode and instrument functions, performance and applications. In last, we provided a brief introduction to the upcoming application of the “Chang’e-7” lunar polar region water molecule analyzer. This instrument comprises a laser absorption spectrometer, which is responsible for the in-situ analysis of H2O and HDO, and a time-of-flight mass spectrometer that enables the analysis of gas molecules with mass numbers < 200 amu, such as H2O and CH4. The scheme can support in-situ analysis of water ice for lunar south pole landing missions.
  • Study on Zero Relative Radial Acceleration Region of Formation near Sun-Earth Libration Points under Solar Radiation Pressure
    LI Zhenyu, LI Xiangyu, QIAO Dong, HUO Zhuoxi
    2023, 10(6): 631-640. https://doi.org/10.15982/j.issn.2096-9287.2023.20220112
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    Formation interferometry near the Sun-Earth libration point is an essential direction for developing high-precision astronomical observation. Keeping the formation configuration stable for a long time is the premise of achieving high-precision measurement. However, the solar radiation pressure will disturb the satellite’s orbit, which challenges the formation configuration’s stability. This paper studies the stable region of formation motion near the libration point under the influence of solar radiation pressure. Based on the Sun-Earth three-body model considering solar radiation pressure, then linearizing the dynamic equation near the reference trajectory of the formation, the analytical expression of the zero relative radial acceleration region near the chief satellite is derived. It is found that the zero relative radial acceleration region is a quadric surface passing through the reference trajectory. The evolution characteristics of zero relative radial acceleration region are further analyzed, and the variation law of region distribution with reference trajectory type, amplitude, and phase is given. Finally, the formation configuration evaluation indexes such as shape, size, and coplanarity are defined. The formation configuration design and control method based on zero relative radial acceleration region is proposed and applied to the design of the five-satellite formation mission. The simulation results show that the formation configuration is bounded within 70 days, and the change rate of the relative distance between the chief satellite and deputy satellite is less than 2% in the first 60 days. In this paper, the study of zero relative radial acceleration region under the influence of solar radiation pressure can provide a basis for designing future Sun-Earth libration point interferometry formation orbits.
  • Space-Based Orbit Determination and Time Synchronization Method for Three Typical Cislunar Orbits
    PU Jinghui, LI Shuanglin, LIU Jiangkai, GUO Pengbin, WANG Wenbin
    2023, 10(6): 641-651. https://doi.org/10.15982/j.issn.2096-9287.2023.20230017
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    In this paper, a space-based orbit determination and time synchronization method for Earth-Moon spacecraft was presented. As a “space-based tracking station”, LEO satellite on the one hand receives GNSS navigation signals to achieve high-precision real-time orbit determination and timing；on the other hand, it establishes measurement links with Earth-moon space spacecraft to support the fast and high-precision orbit determination of Earth-moon spacecraft. Compared with ground stations, LEO satellites operate at a faster speed and orbit the Earth in a shorter period. The Earth-Moon spacecraft and its measurement link have the advantages of short invisible time interval, better measurement geometry, and no atmospheric delay in the measurement process. Therefore, using LEO satellite can improve the convergence speed and accuracy of orbit determination. This paper analyzed the space-based orbit determination and time synchronization performance of three typical orbits in Earth-Moon space, including the distant retrograde orbit (DRO), the highly elliptical orbit (HEO) and the Earth-moon transfer orbit. Space-based orbit determination simulation results show that when the LEO satellite position accuracy is high, the convergence time of the three orbits is less than 3 hours, the orbit position accuracy is about 50 m, and the time synchronization accuracy is tens of nanoseconds. Therefore, this method can hopefully solve the problems of limited deployment and heavy burden of ground stations.
  • Orbit Determination and Accuracy Evaluation of Queqiao Relay Satellite for Orbit Maintenance
    KONG Jing, XIE Jianfeng, HU Guolin, LIU Junqi, MA Chuanling, WU Shuran, LI Ke
    2023, 10(6): 652-658. https://doi.org/10.15982/j.issn.2096-9287.2023.20220088
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    The Queqiao relay satellite which is located in the Halo orbit at Earth-Moon L2 libration point，needs to maintain its configuration by wheel off loading and orbit maintenance every 3-4 days. According to the orbit characteristics of the libration point，the influence of the component of the orbit determination error for the orbit control parameters is analyzed in the rotating coordinate system，and it is concluded that the orbit determination error affecting the orbit maintenance effect mainly concentrate on the velocity error of X-Y plane. In this paper，an orbit determination accuracy evaluation method for orbit maintenance control is proposed，the strategy of orbit determination is designed，and the influence of different strategies on orbit determination is evaluated. The orbit accuracy of the relay satellite in mission orbit is evaluated，and the results show that it can provide 1-3 mm/s velocity accuracy for orbit maintenance under the existing TT&C conditions.
  • Automatic Recognition and Detection of Lunar Concave Obstacles Based on Shadow Feature
    LIU Xiaohui, LIU Shiying, LIU Shaoran, WANG Jia, QIAN Xueru
    2023, 10(6): 659-666. https://doi.org/10.15982/j.issn.2096-9287.2023.20220111
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    The widespread impact craters and other concave obstacles on the lunar surface are the key factors threatening the safe landing and roving of the lunar rover. Once trapped, it will bring risks of tilt, landslide, and even rollover to the lunar rover. Therefore, the effective recognition and detection of lunar concave obstacles are conductive to obstacle avoidance, and provide necessary information reference for the safe landing and roving of the lunar rover. Based on the concave obstacles’ feature that there is a one-to-one matching between the shadows and the highlights in the sun, an automatic recognition and detection method for the lunar concave obstacles is proposed. The adaptive dual threshold method is used to automatically separate the shadows and the highlights of the concave obstacles from the background. Each shadow and highlight are clustered the specific position and one-to-one matched using the sunlight direction with the prior forecast information involved. Then the rough extraction of every single concave obstacle are obtained. Finally the original sub-images sequence containing every single concave obstacle is traversed for edge detection and ellipse fitting, which can avoid mutual interference of multiple obstacles and effectively detect the locations and ranges of all concave obstacles.
  • Spectroscopic Study of Aqueous Alteration of Asteroids Based on Carbonaceous Chondrites
    YU Jinfei, ZHAO Haibin, WU Yunzhao
    2023, 10(6): 667-676. https://doi.org/10.15982/j.issn.2096-9287.2023.20220077
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    The aqueous alteration spectral features of carbonaceous chondrites for were studied for future volatile-rich asteroids exploration and remote sensing. The 1-20 μm infrared spectral features and petrographic characteristics of 15 carbonaceous chondrites with different alteration degrees were analyzed, and the spectral variation laws of the aqueous alteration were summarized. The findings demonstrate that as the degree of alteration of carbonaceous chondrites increases, the 3 μm absorption band, which indicates phyllosilicates and water molecules, and the 6 μm absorption band, which indicates only water molecules, both features increasing in strength and absorption centers shift to the short-wave. With more alteration, the 3 μm absorption band sharpens and resembles serpentine’s 3 μm absorption feature. However, as the degree of alteration increases, the 6 μm absorption band shape does not significantly change. The degree of alteration also affects the spectral shape of the 10-13 μm region. This region indicates silicate features. The 12.4 μm /11.4 μm reflectance ratio reduces as a result of the conversion of anhydrous silicates to phyllosilicates. Also discuss possible effects that the spectra and parameters discovered during this study may have on the outcomes from asteroids.
  • Study of Terrain Shading Judgment on Ceres Surface and Its Solar Radiation Simulation
    LIU Wei, CHEN Nan
    2023, 10(6): 677-688. https://doi.org/10.15982/j.issn.2096-9287.2023.20220102
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    As solar radiation is an important source of energy received by the surface of the planets in the solar system, accurate modeling of solar radiation on the surface of Ceres is crucial for studying the thermal environment. However, the highly undulating terrain on Ceres makes determining terrain shading coefficients challenging. While the ray tracing method can accurately determine terrain shading coefficients, it is limited by the search radius. In the paper, it examines the effects of seasonal differences, landform types, and study area size on solar radiation simulation, and concludes that a minimum threshold search radius of 74 km is required to determine actual terrain shading. Using this radius, the paper simulates solar radiation over a solar day and finds that the search radius required for accurate shading information varies with time of year and landscape type. Surface faults are most consistently influenced by the search radius, while volcanic landscapes are most significantly influenced. The global solar radiation distribution of Ceres shows a gradual decrease from low to high latitudes. Results improve the theory and method of solar radiation modeling and provide data and theoretical support for future exploration of Ceres.