Dielectric Constant Inversion And Component Analysis Of Lunar Subsurface Based On The Lunar Penetrating Radar Onboard Chang’E-3

In the field of remote sensing on the moon, it is particularly important to study th e electrical properties of different lithology units on lunar surface and their depth chan ge of gradient through scientific means for modeling the lunar subsurface radar wave propagation and solving the different understandings and the opposite conclusions of predecessors. Because there are some different understandings and opposite conclusio ns on the radar wave of lunar satellite radar data and reflective and depth detection un der lunar surface.The result data achieved from work which includes read, data mosaic, gain, digital filtering for LPR Channel-1 data from Chang’E-3 shows that there are two obvious reflection interfaces near 180 ns and 640 ns. Based on time-depth conversion formulas, two layer interfaces can be obtained separately at 10 meter and 40 meter under the moon’s surface, and within 10 meters is the lunar soil layer.Through the establishment of equivalent stochastic media models with different lengths a, b and fuzzy factor r, the writer analyze the factors which influence the model. Based on the effective medium theory and FDTD numerical simulation calculation method, the writer selected the appropriate parameters, built a l unar equivalent stochastic media model, optimized the model with cone function and got the higher accuracy moon three layers stochastic media forward models and lunar penetrating radar electromagnetic response profile. All the results provide a reliable forward data for verifying the lunar subsurface dielectric constant inversion model in later period.Thoroughly researching the band-limited impedance(BLIMP) inversion theory to verify the method of dielectric constant inversion, taking the stochastic media model of the lunar penetrating radar forward data as a basis, through multiple inversions, accomplishing selection of band-limited impedance inversion model parameters and the inversion of dielectric constant,we can found from the inversion results, that the dielectric constant inverse result is finely anastomose with that of the model set, indicating that band-limited inversion method can be used in the inversion of dielectric constant based on the lunar penetrating radar of Chang ’E-3.On the base of the LPR Channel-1 data from Chang’E-3, using the verified band-limited impedance method to inverse the dielectric constant distribution of two-dimensional stochastic media, the inversion results show that the interface of every layer is clear, the distribution characteristics of dielectric constant reflect the certain randomness, the dielectric constant values of 0~10 meters are in the range of 2.3310~3.9086, it is anastomose with that of lunar regolith real samples. the dielectric constant values of 10~40 meters are in the range of 6.5119~7.5858, most of the dielectric constant is about at 7, under 40 meters, the distribution of dielectric constant are in the range of 7.5010~8.4449, most of the dielectric constant is about at 8, they are consistent comparing with the measured value of lunar mare basalts real samples.Based on lunar regolith equivalent medium model theory, using the regolith dielectric constant inversion results, simulating invert the lunar regolith average mineral content of 0~10 meters under the surface, plagioclase content is in the range of 20.93%~29.04%; olivine content is in the range of 37.28%~45.02%; clinopyroxene content is in the range of 50.44%~60.96%; ilmenite content is in the range of 6.79%~8.08%. Comparing the lunar regolith mineral content inversion results with lunar regolith real samples collected from the Apollo and Luna landing site, Chang E-3 soils mineral composition inverted by Zongcheng Ling et al using APXS data and the lunar minerals composition inversion result based on M3 data, which indicates that the inversion result of lunar regolith layer plagioclase, clinopyroxene and ilmenite is viable, but there is a certain deviation in the inversion results of olivine.Eighteen pieces of basalt are selected as the samples to simulate lunar rock for measuring dielectric constant and duty ratio of rock section(total area of porosity in per unit area of rock section) collecting from Xilinhot, Mongolia, Arxan, Heilongjiang Province, Wudalianchi, Heilongjiang Province, Zhangjiakou, Hebei Province, Jingpo Lake, Heilongjiang Province and Huinan area of Jilin Province. By analyzing the relationship between the dielectric constant and duty ratio of rock section of the simulate samples, reach a rule that the dielectric constant of the simulate samples decreases with increasing porosity of rock section, indicating that the lunar depth increases, the rock material structure more compact. Compare and analysis the measurement results of real rock samples and results of band-limited impedance inversion, the inversion results show that the value of dielectric constant in range of 10~40 m are most at about 7, which is close to the measurement results of XL-01, XL-03, XL-12 from Xilinhot, Mongolia and sample L5-04 from Zhangjiakou, Hebei Province, the dielectric constant value of the simulate sample the lunar rock under 40 meters is about at 8, which is coincident with the measurement results of sample L5-01 and L4-09 from Zhangjiakou, Hebei Province, which not only shows band-limited impedance inversion results are reliable, also said the occurrence and lithofacies of rocks under 10 ~ 40 meters of lunar surface are similar to the basalt in Xilinhot, Mongolia and the basalts in Zhangjiakou, Hebei Province, a part of rocks exist a cer tain pore inside and another part of the rock structure is compact. The occurrence and lithofacies of rocks under more than 40 meters of lunar surface are similar to the basalt in Zhangjiakou, Hebei Province, the material structure of rock is compact, and there is almost no pore exits. Providing some practical value for lunar exploration research.