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Accueil du site → Doctorat → Australie → 2000 → Mapping surface mineralogy and scattering behaviour using the mid-infrared airborne CO2 laser spectrometer (MIRACO2LAS)

Curtin University of Technology (2000)

Mapping surface mineralogy and scattering behaviour using the mid-infrared airborne CO2 laser spectrometer (MIRACO2LAS)

Cudahy, Thomas John.

Titre : Mapping surface mineralogy and scattering behaviour using the mid-infrared airborne CO2 laser spectrometer (MIRACO2LAS)

Auteur : Cudahy, Thomas John

Grade : Doctor of Philosophy Ph.D 2000

Université de soutenance : Curtin University of Technology.

Résumé
Airborne, high spectral-resolution, thermal infrared (TIR) MIRACO2LAS reflectance data were evaluated for mapping surface mineralogy and scattering behavior for a variety of semi- arid, geological test sites in Australia. MIRACO2LAS is a rapidly-tuned, airborne C02 laser system that measures backscattered (bi-directional) reflectance at 100 wavelengths between 9.1 and 11.2 gm for 2 meter footprints in line profile mode. An operational methodology is described that permits reduction of the raw airborne signal to ground reflectance. This ground reflectance has two major properties, namely : mineralogical variations ; and surface scattering. Comparisons between the airborne MIRACO2LAS spectra and laboratory directional hemispherical reflectance (DHR) spectra show the same spectral shapes though differences in average reflectance (albedo) occur for some types of rocks. The minerals identified using MIRACO2LAS include silicates (for example, quartz, microcline, Na-plagioclase, almandine, spessartine, talc, actinolite, tremolite and kaolinite) and carbonates (dolomite and magnesite) as well as vegetation (dry and green). Many of the diagnostic spectral features that allow identification of these materials are narrow (<0.2 gm) making them difficult to detect with low spectralresolution TIR systems like the airborne TIMS and satellite-borne ASTER. Based on an empirical relationship between the minimum and maximum reflectance established using laboratory DHR spectra, a method is proposed that allows the use of MIRACO2LAS data to identify surfaces that are characterized by Lambertian or specular scattering, including any wavelength-dependency. The MIRACO2LAS results show that Lambertian-type scatterers include soils and many types of rocks. Specular-type scatterers include water and anisotropic rocks bearing minerals talc and chlorite. Mineral mixtures of isotropic and anisotropic scatterers can generate wavelength-dependent scattering phenomena that can be detected with MIRACO2LAS. This ability to map a given pixel’s scattering behaviour, means that MIRACO2LAS data can be used to test the accuracy of temperature-emissivity separation (TES) methods applied to passive multispectral TIR data, provided the surface is mapped as a Lambertian scatterer. This possibility was examined for the Alpha TES method that was applied to airborne TIMS data. These results have significant consequences for the next generation of operational TIR remote sensing systems

National Library of Australia

Page publiée le 29 février 2008, mise à jour le 15 décembre 2018