Ground-based radio observations below 30 MHz are susceptible to the ionosphere of the Earth and the radio frequency interference.Compared with other space mission concepts,making low frequency observations using an in...Ground-based radio observations below 30 MHz are susceptible to the ionosphere of the Earth and the radio frequency interference.Compared with other space mission concepts,making low frequency observations using an interferometer array on lunar orbit is one of the most feasible ones due to a number of technical and economic advantages.Different from traditional interferometer arrays,the interferometer array on lunar orbit faces some complications such as the three-dimensional distribution of baselines and the changing sky blockage by the Moon.Although the brute-force method based on the linear mapping relationship between the visibilities and the sky temperature can produce satisfactory results in general,there are still large residual errors on account of the loss of the edge information.To obtain the full-sky maps with higher accuracy,in this paper we propose a novel imaging method based on reweighted total variation(RTV)for a lunar orbit interferometer array.Meanwhile,a split Bregman iteration method is introduced to optimize the proposed RTV model so as to decrease the computation time.The simulation results show that,compared with the traditional brute-force method,the RTV regularization method can effectively reduce the reconstruction errors and obtain more accurate sky maps,which proves the effectiveness of the proposed method.展开更多
With the increasing scarcity of Earth’s resources and the development of space science and technology,the exploration, development, and utilization of deep space-specific material resources(minerals, water ice, volat...With the increasing scarcity of Earth’s resources and the development of space science and technology,the exploration, development, and utilization of deep space-specific material resources(minerals, water ice, volatile compounds, etc.) are not only important to supplement the resources and reserves on Earth but also provide a material foundation for establishing extraterrestrial research bases. To achieve large depth in-situ condition-preserved coring(ICP-Coring) in the extreme lunar environment, first, lunar rock simulant was selected(SZU-1), which has a material composition, element distribution, and physical and mechanical properties that are approximately equivalent to those of lunar mare basalt. Second, the influence of the lunar-based in-situ environment on the phase, microstructure, and thermal physical properties(specific heat capacity, thermal conductivity, thermal diffusivity, and thermal expansion coefficient)of SZU-1 was explored and compared with the measured lunar rock data. It was found that in an air atmosphere, low temperature has a more pronounced effect on the relative content of olivine than other temperatures, while in a vacuum atmosphere, the relative contents of olivine and anorthite are significantly affected only at temperatures of approximately-20 and 200 ℃. When the vacuum level is less than100 Pa, the contribution of air conduction can be almost neglected, whereas it becomes dominant above this threshold. Additionally, as the testing temperature increases, the surface of SZU-1 exhibits increased microcracking, fracture opening, and unevenness, while the specific heat capacity, thermal conductivity,and thermal expansion coefficient show nonlinear increases. Conversely, the thermal diffusivity exhibits a nonlinear decreasing trend. The relationship between thermal conductivity, thermal diffusivity, and temperature can be effectively described by an exponential function(R^(2)>0.98). The research results are consistent with previous studies on real lunar rocks. These research findings are expected to be applied in the development of the test and analysis systems of ICP-Coring in a lunar environment and the exploration of the mechanism of machine-rock interaction in the in-situ drilling and coring process.展开更多
The Chang’E-6 mission will first land on the far side of the moon and bring lunar samples back.As a hyperspectral imager aboard the Chang’E-6 lander,the Lunar Mineralogical Spectrometer(LMS),will achieve the goal of...The Chang’E-6 mission will first land on the far side of the moon and bring lunar samples back.As a hyperspectral imager aboard the Chang’E-6 lander,the Lunar Mineralogical Spectrometer(LMS),will achieve the goal of spectral detection and mineral composition analysis in the sampling area,and the data of LMS will also be compared with the results of the returned sample laboratory measurements.Visible and near-infrared hyperspectral remote sensing is an effective tool for lunar minerals identification and quantification.The ground validation experiment can be used to evaluate the detection ability of the LMS.According to the modal abundances of lunar minerals and glasses of APOLLO samples,binary mixed samples,ternary mixed samples,and seven-membered mixed samples were prepared.The samples were ground and stirred homogeneous to about 200 mesh(median particle size about 75μm),to simulate the soil state of the lunar surface.Under the laboratory ambient condition,the 480–3200 nm spectral data of the samples were acquired using the Engineering Qualification Model(EQM)of Chang’E-5 LMS,the performance of which is consistent with the flight model of Chang’E-6 LMS.By fitting the mixed samples’spectral data of the EQM using the Modified Gaussian Methods,the following conclusions can be drawn:The subtle spectral changes of mixed samples can be detected.The modal abundance of low-Ca pyroxene,high-Ca pyroxene,and plagioclase can be derived based on the spectral parameters such as absorption position,depth or width of the mixed samples,and the correlation coefficients R2are better than 82%,indicating that the LMS has good quantitative detection capability.展开更多
针对月壤钻取采样过程中存在大颗粒岩块情况进行三维离散元动态仿真分析。建立考虑扭转、弯曲力矩及等效引力作用的新型三维离散元月壤模型,通过三轴仿真试验进行细观参数标定,得到黏聚力为0.90 k Pa,内摩擦角为42.25°的满足真实...针对月壤钻取采样过程中存在大颗粒岩块情况进行三维离散元动态仿真分析。建立考虑扭转、弯曲力矩及等效引力作用的新型三维离散元月壤模型,通过三轴仿真试验进行细观参数标定,得到黏聚力为0.90 k Pa,内摩擦角为42.25°的满足真实月壤宏观力学指标的仿真模型。针对月壤内层存在大颗粒情况设计4种采样工况分别进行仿真分析,监测大颗粒运动轨迹与采样效率,发现了"旋入效应"、"纵向运移效应"与"阻塞效应",仿真结果表明岩块粒径大小直接影响采样结果:当岩块粒径小于钻头"虚拟切削圆"时,其无论存在于任何位置对采样效率与后续样品缠绕收集均无明显影响;当岩块粒径大于"虚拟切削圆"时,阻塞现象严重,样品收集困难,极易导致采样失败。研究结论对月壤钻取采样控制设计与钻具结构设计具有重要的工程参考价值。展开更多
基金supported by the Specialized Research Fund for State Key Laboratories under Grant 202217the Key Laboratory of Solar Activity and Space Weather(NSSC)under Grant E26600021S。
文摘Ground-based radio observations below 30 MHz are susceptible to the ionosphere of the Earth and the radio frequency interference.Compared with other space mission concepts,making low frequency observations using an interferometer array on lunar orbit is one of the most feasible ones due to a number of technical and economic advantages.Different from traditional interferometer arrays,the interferometer array on lunar orbit faces some complications such as the three-dimensional distribution of baselines and the changing sky blockage by the Moon.Although the brute-force method based on the linear mapping relationship between the visibilities and the sky temperature can produce satisfactory results in general,there are still large residual errors on account of the loss of the edge information.To obtain the full-sky maps with higher accuracy,in this paper we propose a novel imaging method based on reweighted total variation(RTV)for a lunar orbit interferometer array.Meanwhile,a split Bregman iteration method is introduced to optimize the proposed RTV model so as to decrease the computation time.The simulation results show that,compared with the traditional brute-force method,the RTV regularization method can effectively reduce the reconstruction errors and obtain more accurate sky maps,which proves the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China(Nos.U2013603 and 52225403)the Program for Guangdong Introducing Innovative and Entrepreneurial Teams(No.2019ZT08G315)the Shenzhen National Science Fund for Distinguished Young Scholars(No.RCJC20210706091948015).
文摘With the increasing scarcity of Earth’s resources and the development of space science and technology,the exploration, development, and utilization of deep space-specific material resources(minerals, water ice, volatile compounds, etc.) are not only important to supplement the resources and reserves on Earth but also provide a material foundation for establishing extraterrestrial research bases. To achieve large depth in-situ condition-preserved coring(ICP-Coring) in the extreme lunar environment, first, lunar rock simulant was selected(SZU-1), which has a material composition, element distribution, and physical and mechanical properties that are approximately equivalent to those of lunar mare basalt. Second, the influence of the lunar-based in-situ environment on the phase, microstructure, and thermal physical properties(specific heat capacity, thermal conductivity, thermal diffusivity, and thermal expansion coefficient)of SZU-1 was explored and compared with the measured lunar rock data. It was found that in an air atmosphere, low temperature has a more pronounced effect on the relative content of olivine than other temperatures, while in a vacuum atmosphere, the relative contents of olivine and anorthite are significantly affected only at temperatures of approximately-20 and 200 ℃. When the vacuum level is less than100 Pa, the contribution of air conduction can be almost neglected, whereas it becomes dominant above this threshold. Additionally, as the testing temperature increases, the surface of SZU-1 exhibits increased microcracking, fracture opening, and unevenness, while the specific heat capacity, thermal conductivity,and thermal expansion coefficient show nonlinear increases. Conversely, the thermal diffusivity exhibits a nonlinear decreasing trend. The relationship between thermal conductivity, thermal diffusivity, and temperature can be effectively described by an exponential function(R^(2)>0.98). The research results are consistent with previous studies on real lunar rocks. These research findings are expected to be applied in the development of the test and analysis systems of ICP-Coring in a lunar environment and the exploration of the mechanism of machine-rock interaction in the in-situ drilling and coring process.
文摘The Chang’E-6 mission will first land on the far side of the moon and bring lunar samples back.As a hyperspectral imager aboard the Chang’E-6 lander,the Lunar Mineralogical Spectrometer(LMS),will achieve the goal of spectral detection and mineral composition analysis in the sampling area,and the data of LMS will also be compared with the results of the returned sample laboratory measurements.Visible and near-infrared hyperspectral remote sensing is an effective tool for lunar minerals identification and quantification.The ground validation experiment can be used to evaluate the detection ability of the LMS.According to the modal abundances of lunar minerals and glasses of APOLLO samples,binary mixed samples,ternary mixed samples,and seven-membered mixed samples were prepared.The samples were ground and stirred homogeneous to about 200 mesh(median particle size about 75μm),to simulate the soil state of the lunar surface.Under the laboratory ambient condition,the 480–3200 nm spectral data of the samples were acquired using the Engineering Qualification Model(EQM)of Chang’E-5 LMS,the performance of which is consistent with the flight model of Chang’E-6 LMS.By fitting the mixed samples’spectral data of the EQM using the Modified Gaussian Methods,the following conclusions can be drawn:The subtle spectral changes of mixed samples can be detected.The modal abundance of low-Ca pyroxene,high-Ca pyroxene,and plagioclase can be derived based on the spectral parameters such as absorption position,depth or width of the mixed samples,and the correlation coefficients R2are better than 82%,indicating that the LMS has good quantitative detection capability.
文摘针对月壤钻取采样过程中存在大颗粒岩块情况进行三维离散元动态仿真分析。建立考虑扭转、弯曲力矩及等效引力作用的新型三维离散元月壤模型,通过三轴仿真试验进行细观参数标定,得到黏聚力为0.90 k Pa,内摩擦角为42.25°的满足真实月壤宏观力学指标的仿真模型。针对月壤内层存在大颗粒情况设计4种采样工况分别进行仿真分析,监测大颗粒运动轨迹与采样效率,发现了"旋入效应"、"纵向运移效应"与"阻塞效应",仿真结果表明岩块粒径大小直接影响采样结果:当岩块粒径小于钻头"虚拟切削圆"时,其无论存在于任何位置对采样效率与后续样品缠绕收集均无明显影响;当岩块粒径大于"虚拟切削圆"时,阻塞现象严重,样品收集困难,极易导致采样失败。研究结论对月壤钻取采样控制设计与钻具结构设计具有重要的工程参考价值。
