SAR Simulation of Lunar Surface Based on Rocks Abundance from NAC

At present, there is relatively little research on the fine structure of the lunar regolith surface. Parameters acquisition of surface rocks rely on rock abundance data estimated by radiant brightness temperature. The rock abundance data cover the entire lunar surface. However, the resolution is very low and cannot reflect the true details of the unique topographic structure of the lunar surface, such as craters, lunar streams, creases, and scattered surface rocks. These lead to the problem that the resolution is not informative enough for practical reference in both lunar surface detection and landing site selection of the lander. On the other hand, the digital terrain model (DTM) has meter-scale resolution, and the LRO Narrow-angle Camera (NAC) is able to show the fine structure of the lunar surface. The stones on lunar surface show obvious brightness difference between the sunny side and the back side under sunlight in high-precision optical images. It is possible to obtain the distribution, proportion and location information of the surface rocks from high-resolution optical images, because of the good identification between the protruding meter-scale rocks and small crater structures. Secondly, the approximate distribution of the surface stones is determined by the optical characteristics of the stones in the NAC image. Therefore, this paper first uses DTM data to obtain the geometric model of the study area. Then, VRT is presented to simulate the scattering process of radar echoes in lunar regolith. In this process, the regolith scattering and the secondary scattering of surface rocks are considered to be the main radar scattering. Finally, the mapping projection algorithm (MPA) is used to simulate radar imaging mechanism. The simulation results of backscattering are compared and analyzed with the actual echo observed by Mini RF radar. The distribution trend of echo intensity has good consistency, and the rationality of adding surface stones is also verified.