Principles And Methods Of Reflectance Spectroscopy And Thermal Emission And Their Application To Lunar Exploration

It is important to know the surface distribution of rock-forming minerals and the types of rocks on the lunar surface. It can tell us the history and evolution of the moon. There are two methods which are suitable to investigate the mineralogy of the moon and can be used on remote-sensing platforms, which includes reflectance spectroscopy and thermal emission spectra. So the principle and method of reflectance spectroscopy and thermal emission spectra are chosen as the main topic of the thesis.The energy source of the reflectance spectroscopy comes from the Sun. Its energy is mainly distributed in the ultraviolet-visible spectral range. The photos in the spectral range have enough energy to excite electrons of some transition metals from lower energy level to higher energy level, which leads to the absorption features. The main transition metal on the lunar surface is Fe2+.There are three main rock-forming minerals on the lunar surface, which are olivine, plagioclase and pyroxene respectively. The Fe2+ ion is surrounded by different electron field in different minerals. So the Fe2+ ion has different energy levels. So the energy needed to excite the electrons of the outer shell is different, photos of different color are absorbed. Then the centre wavelength of absorption feature is different. The position and the strength of the absorption feature can be used to identify minerals.There are many factors influencing the characteristics of the reflectance, including the space weathering, the systematic changes of the chemistry of minerals, particle size and the temperature.The Moon is an airless body, the surface crystalline rocks and breccias (generated in large impacts) are directly exposed to space. The "space weathering" process occurs. The weathering (soil maturation) process also creates tiny (submicroscopic, aka nanophase) blebs of metallic iron (Fe? by the reduction of ferrous iron in minerals and glasses. The submicroscopic metallic iron has a strong effect on the spectral reflectance properties - decreasing the overall reflectance, decreasing the contrast in the "1 urn" band, and causing a reddening of the spectral slope.There are two types of reflectance spectroscopy. One is of high spectral resolution called continuous spectra. The other is multi-spectral remote-sensing data with poor spectral resolution. At present, the continuous spectrum is mainly gained using earth-based telescopes, so its spatial resolution is rather poor. But the multi-spectral data is usually gained by imaging spectroscopy; itis of high spatial resolution depending on the performance of the instrument. To interpret the continuous spectra, the continuum background is needed to be removed to reveal the absorption feature. Having removed the continuum, you can use various spectral parameters to interpret the continuum-removed spectra. To use the multi-spectral data, spectral ratio and spectral curvature are used to describe the strength and the shape of the 1-micrometer character respectively. But it is obvious that the calibration of radiance become critically important. Minor errors can lead to misleading conclusions. The application of hyper-spectral remote sensing will bring us more information about the moon.The moon not only reflects the incoming radiation from the sun. It also emits energy continuously in the form of heat. It is also called thermal emission. The peak of the thermal emission mainly lies in the region of mid-infrared spectrum. The energy of mid-infrared spectrum can meets the demands for the vibration of some small molecules and lattice vibration of some inorganic solid substance, such as silicates minerals. Different substances has different vibration absorption feature. So it can be used to identify minerals directly. The technique is also called T1R. In this paper, the T1R spectra of some important minerals are introduced. The fundamental vibrational modes of silicates are dominated by Si-0 stretching and bending modes (Al can sub for Si), the Si-O stretching mode corresponds to 8-12 um regions, and the bend m...