Passive Sensing Mechanism Of The Lunar Surface Medium And The Thickness Of The Inversion

The aim of this paper is to find a method to estimate the thickness of lunar soil from the values measured by lunar microwave radiometer. Lunar surface can be regarded approximately as two-layered medium composed of lunar soil and lunar rock. Therefore, in this paper, two-layered medium is mainly discussed.Firstly, the paper introduces briefly the detecting principle of microwave radiometer and the scheme of lunar microwave radiometer. Based on propagation matrix, an algorithm to get reflectivity of layered medium is brought in. By means of the method, the reflectivity expression of two-layer medium is obtained.Secondly, the paper emphasizes particularly on introducing two different approaches to brightness temperature (for short, TB) of layered medium. One is based on RT theory (called RT method), and the other is on the basis of DGF (called DGF method). According to the methods, the relational expressions between TB of two-layer medium and the thickness of its first layer (for short, thickness) are achieved respectively. By comparing the two methods, we find that they have an obvious difference. The relationship between TB and thickness from RT method is one-to-one, but the relation from DGF method isn't.Then an algorithm on detecting depth of microwave radiometer is proposed according to its characteristics. Under special conditions, we analyze the tendencies of detecting depth vs. observation angle, frequency and thickness.Finally, two inverse methods are brought forward for the difference of RT method and DGF method. To RT method, its depth inverse expression can be derived directly from the TB expression. But to DGF method, it is difficult. Therefore according to least square method, approximate values of thickness are obtained by comparing simulated measured values and theoretic values.After comparing the inverse results from different method, RT method is chose to estimate the thickness of lunar soil.