Research On Calculating Method Of Microwave Radiation Brightness Temperature From The Moon With Rough Surface

Detecting the lunar regolith thickness (LRT) is a valuable research to the exploitation andutilization of lunar resources in the future. One of the crucial research domains in estimating LRTis establishing an accurate and comprehensive transmission model of microwave radiationthrough lunar surface. The study on surface roughness of the lunar regolith is one of thedifficulties, and the influence of surface roughness on brightness temperature (BT) is about to besolved, also is the object of studying in this paper. This paper is based on the national863high-tech project’s significant research subject lunar exploration project. The relationship betweensurface roughness and microwave radiation BT is modeled in this paper, and the detectedbrightness temperature data from the Microwave Radiometer carried by CE-2satellite is used asthe criterion.In this paper, the terrain roughness information within the scope of at the Apollo landingsites is analyzed based on the elevation data with resolution of7km from CE-1laser altimeter.Then the modification of the large scale roughness to the effective solar irradiation is applied tothe boundary condition in heat conduction equation, large-scale rough surface layered model isestablished to get the temperature profile. Additionally, the moon surface can be considered as flatsurface in large scale. However, the surface can also be treated as steep in smaller scale. Thefluctuation of such steep surface is measured in centimeter or even millimeter, which is close thewavelength of high frequency incident wave. This characteristic makes it possible to establish amicrowave radiation brightness temperature estimation model on rough surface based on radiatetransfer theory, rough surface random scattering theory and Second-order Small PerturbationMethod (SPM). Therefore, applying both large scale temperature section calculation model andmicro scale brightness temperature radiation transmission model to our new model will enable itto be more flexible and robust.The simulation results suggest that sun radiation from the moon decreases corresponding tothe increase of the moon surface roughness, and the moon surface radiation brightnesstemperature also decreases. Among the four channels in microwave radiometer, the microwavewith3GHz frequency has longest wavelength and has the best capability of penetrating in lunarsoil, therefore this type of microwave becomes the most valuable medium to inversion method oflunar regolith layer thickness. Furthermore, the approach of including micro scale roughness tothe estimation model amends the result obtained from large scale. The amended result is closer toactual measurement values than that without amendment at frequencies of3GHz,7.8GHz and19.35GHz.