| Most surfaces in nature can be used as random rough surfaces meet certainprobability density distribution. The investigation of electromagnetic scattering fromrough surface of the layered structure, it has important academic value andapplication prospects on many fields, such as remote sensing, radar detection,recognition of underground targets. In our study, a numerical simulation method ofthe electromagnetic scattering field of a layered lunar surface is introduced. AndLunar Radar Sounder (LRS), a space-borne high frequency system, is utilized asexcitation source; the research background has been used lunar environment.Lunar Radar Sounder is an effective tool to obtain subsurface structural features,due to the radar wave can penetrate underground a few hundred meters to severalkilometers depth. The main contents are as following:(1) The Gaussian random surfaces are employed to represent the lunar maresurface. Based on statistical property of impact craters and randomly producingcrater in mare surface, the surface feature in highland region is numericallygenerated. Then, two numerical subdivision methods (the triangulated regularnetwork (TRN) and the triangulated irregular network (TIN)) are employed to dividethe surface into discrete triangular mesh as a digital elevation model. And a minimalnumber of meshes are used to characterize the undulating surface.(2) The numerical simulation of LRS observation of layered structure isdeveloped by utilizing the Kirchhoff approximation (KA) of rough surface scattering,the ray tracing and Stratton-Chu integral formula. Based on TRN simulation withsmall mesh dimension, the echoes curve is continuous but it has a huge number ofmeshes, and leads to complicated computations (about the order of O(N3), whereN is the number of meshes); while in the case of TIN, it can effectively reducecomputation task. The surface mesh refinement is developed to optimize everytriangular mesh in TIN, and make the simulation result reach the performance ofTRN simulation.(3) Finally, the influence of changeless on surface and subsurface roughness to the simulation of single pulse radar detect is discussed. Radar received scatteringfield and its range images are numerically simulated when it detect a layered surface. |
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