基于FDTD的月壤分层雷达探测正演模拟

Forward modelling of the lunar regolith layer using radar detection based on FDTD

"嫦娥三号"巡视器上搭载的测月雷达通过500MHz频率的天线,对巡视路线上的月壳浅层结构进行剖面式观测,能探测到月球地底下30m深土壤层的结构。为了更好地分析测月雷达的探测结果,文中对月壤分层进行正演模拟,月岩层的介电常数采用与"嫦娥三号"登月点位置最近的Apollo 15的电性参数近似代替,月壤的介电常数是一个和密度相关的值且随深度的变化而变化。根据以上参数建立模型,基于时域有限差分(FDTD)原理,利用GprMax对月壤分层结构进行模拟,建立的模型包括月表介电常数随深度变化二层模型和月岩层存在下界面三层模型,并对其波形特征进行分析,找到月壤层次划分的一般规律,对"嫦娥三号"测月雷达数据的分析提供理论依据。

Lunar Penetrating Radar equipped on the rover of CE-3can observe the shallow structure of lunar surface on across-sectional observational style and detect 30 meters soil layer structure under the lunar by the antenna of 500 MHz.In order to analyze the exploration results of lunar penetrating radar better,this paper builds forward modelling using ground penetrating radar technology in order to study the lunar regolith layer;we adopted the electrical parameter of Apollo 15 which is nearest to the landing position of CE-3as the dielectric constant of rock layer;the dielectric constant of the lunar regolith is a value related to density and varied with depth.To establish the model according to the above parameters,based on the finite difference time domain（FDTD）principle,the lunar regolith layer was simulated by the GprMax,and the established model included the model of the surface dielectric constant change with depth and water-ice distribution simulation inside the lunar soil,aiming for finding the general rules of the lunar regolith layer and the thickness of the water-ice.We have analyzed the wave features of radar reflectance wave,which can provide the theoretical basis for future moon probe program.