Study On Bidirectional Reflectance Model Of Minerals On Lunar Surface

Bidirectional reflectance character is one of the most reliable evidences todetermine the specific category and exact amount of minerals on lunar surface.Throughout the world-wide lunar exploration events, different photometric modelwere used to imitate the photometric behavior of lunar surface and to process relevantspectra. Hapke models are the approximate analytical solutions to the equation ofradiative transfer. They were successfully used in the imitation of spectra of planetarysurface and inversion of photometric factors, while the most important contributionthey made is achievement of translation between bidirectional reflectance andsingle-scattering albedo as well as other types of bidirectional reflectance. B. Hapkeput forward and verified a conclusion that the singly albedo of mixture is the linearsum of albedo of end member particles weighed by their relative cross section area,which is the mathematical foundation of my research.When it comes to the correction for macroscopic roughness, B. Hapke only tookthe mean slope into consideration, ignoring the other factors. Based on this fact, somemodification were made by adding the effect of aspect and visible pixels around,gaining a new Hapke model with fully consideration of topographic factors on ourown, which could be the most valuable part in this research.Before the inversion of distribution of rock-forming minerals(plagioclase, olivine,clinopyroxene, orthopyroxene) on lunar surface, we design a experiment about thebidirectional characters of these four minerals and the mixing spectra. Firstly, Theeffect of observation geometry conditions was studied: the range of incidence angleand emergence angle was set0~60°while the range of azimuth angle was0~360°,After measuring the corresponding reflectance, the focus of research was switched tothe effect of particle diameters when the mineral samples had been sieved into fourgroups:6~120μm、120~150μm、150~180μm、180~250μm and eventually, all thesamples were measured and some regulations were summaries. Secondly, the mixingmethodology of spectra of mixture was began to studied with four samples mixed byplagioclase and clinopyroxene. The result said that there is a approximate linearrelationship between mixture and end member minerals and the accuracy of simplifiedHapke model (isotropic model) was acceptable when it was applied to the current hyperspectra data of lunar surface.Due to the true topography of lunar surface, the isotropic Hapke model withcomplete macroscope topography correction was used to the unmixing of M3data.Before the final inversion, a test of this model was put opon the region around thelanding site of Apollo16, and the final result is acceptable.At last, model mentioned above was applied to the spectra unmixing of M3data,obtained by Indian satellite” Chandrayaan-1”. After testing the feasibility of the modelby comparing the inversion results with the actual mineral abundance of samplesgathered near Apollo17landing site, the prime landing area of “CE-3”-Sinus Iridiumwas chosen as the region of interest, and the final achievement is distribution ofdominant rock-forming minerals of this region.