Theory And Application Of Inversions Of Lunar Surface Parameters From Chang’ E-1Microwave Radiometer’s Observations

During the long history of geological evoluation, it becomes to form a craterd-topography and a regolith layer covering most parts of the lunar surface because of the influence of volcanic activities and the impacts of other meteorolites and small objects. And as a result of lack of atmosphere, the regolith, exposed to the out space, is always subject to the radiation of solar-wind particles and cosmic rays. Thus, the regolith layer is rich in various kinds of valuable elements that can be utlilized, such as3He, a kind of clean energy resource. Thus it has significant meanings to evaluate the thickness of the regolith layer as an important index for lunar resources. Furthermore, the lunar geological structure does not only record the formation and evolution history of the Moon, but also is vital to the lunar exploration and utilization. This is also the reason that researches on subsurface structure and lunar temperatures were paid so much attention to in the past few years.China launched its Chang’E-1(CE-1) and Change’E-2(CE-2) satellite successively in2007and2010. It was the first time that a multi-channel microwave radiometer was onboard, aiming at measuring the microwave thermal emission of the whole lunar surface. The CE-3, planned to land at Sinus Iridum on the Moon, is proposed to the agenda as well.Based on the microwave radiation theory and interaction mechanism between the electromagnetic waves and the layered lunar regolith model, this thesis maily focused on analyzing the diurnal variation of physical temperatures of the lunar surface, and inversion of the lunar regolith based on the layered lunar regolith model with a temperature profile. Moreover, a method on inversing the dielectric constant from the CE-1microwave observations was also developed, and this supplies an effective way to investigate the geological information from the microwave thermal explorations.Firstly, on the basis of the microwave radiometer’s observations from CE-1, the specific lunar local time at Sinus Iridum was determined from the local Sun incidence and azimuth angle. Combined with the three-layer lunar regolith model, the diurnal variation of the physical temperatures at Sinus Iridum was investigated from the high frequency channels’microwave data. And then a contrast between the microwave and infrared band thermal radiation in situ was made and the factors in the lunar regolith that may have an influence on the temperature distributions were discussed.Secondly, inversions of the physical temperature profile of the lunar regolith medium and its layer thickness from multi-channel brightness temperature observations of CE-1are discussed. For example, two areas, along the lunar equator and the line of Longitude150°W, the correspondence of the brightness temperature distribution to the lunar topography Digital Elevation Mapping (DEM) is demonstrated, also brightness temperature distributions around the lunar polar regions under poor solar illumination were discussed. Using a three-layer model of thermal radiative transfer, the physical temperature profile of regolith layer and its thickness are inverted. The results are compared with an empirical formular of the physical temperature as a function of latitude which is based on some Apollo measurements.Thirdly, a theoretical analysis of radiative transfer is presented to explain an abnormal phenomenon of diurnal changes in the microwave and infrared thermal observations. Two craters, typically representing the abnormal fresh craters rich in rock abundance and an old one almost with rock free, located at similar latitudes are chosen for comparison of their diurnal temperature change. Using the measurements of CE-1multi-channel microwave radiometer, brightness temperature distributions of these two craters are presented and applied to inversions of the physical temperatures of lunar regolith media, based on a three-layer radiative transfer model. The correlation between the diurnal MW and IR thermal changes of the lunar surface and the rock abundance is discussed.Forthly, the CE-1microwave observations can be well matched from a relatively simple microwave radiative transfer model, and the dielectric constant can be derived from the best fit of parameters. From the inversion results, it is strongly indicated that the compostion of the lunar regolith is different at the lunar maria and highlands, which is consistent with the traditional method that calculating the dielectric constant from the FeO and TiO2content.At last, as a supplyment on active remote sensing research, this thesis also introduces some basic theory on lunar radar sounder and developed a software that can simulate the echoes of the planet surface and subsurface from the radar sounder. It provides some information on judging the subsurface structure and geological information of planets from the real radar sounder echoes in the future.