Publication
Reference
Doute S. (1998). Modélisation numérique de la réflectance spectrale des surfaces glacées du système solaire. Application à l’analyse de spectres de Triton et Pluton et au traitement d’images hyperspectrales NIMS de Io. Thesis, Université Joseph Fourier, Grenoble, France. 280pp.
Names
  • S. Doute
Article and keywords
Title
Modélisation numérique de la réflectance spectrale des surfaces glacées du système solaire. Application à l’analyse de spectres de Triton et Pluton et au traitement d’images hyperspectrales NIMS de Io
Abstract
This thesis comes within the scope of development activities and data analysis created by the increasing use of high resolution spectrophotometry and hyperspecral imaging in the visible and near infrared, for remote sensing of planetary surfaces of the Solar System. These two techniques of observation rely on optical instruments such as ground telescopes equipped with spectrometers, or such as imaging-spectrometers onboard space probes. These instruments record sets of reflected and/or emitted spectra forming hyperspectral images with a variable spatial resolution. As a result of the measurements of solar or thermal radiative fluxes which have propagated by interaction through the surface materials, the spectra a priori contain some precious information about the physical, chemical and structural properties of the uppermost few millimeter or centimeter depth of the extraterrestrial grounds. In particular, the quantitative analysis of high spatial resolution hyperspectral images may give these characteristics over large geographic and temporal scales. In order to achieve such a task, the conception and the development of theoretical and numerical appropriate tools are needed. Within this context, an important part of the work presented here is dedicated to a practical, timely, and effective model calculating the spectral bidirectional reflectance of an icy or mineral stratified surface. The aim of the model is to determine, for any kind of illumination and viewing conditions, the link between the physical, chemical and, structural characteristics of the underlying medium and the corresponding observed spectral signature. The multiple scattering and absorption phenomena, which determine the transfer of the reflected light out of the surface are treated with the "H, X and Y function method" proposed by Chandrasekhar. The method is practically available only for moderately anisotropic media. We extend this domain of validity applying a separate and accurate treatment for the single and double scattering contributions. On the basis of the previous model, we have created and programmed a software which can globally model spectrophotometric curves of non spatially resolved planetary bodies or hyperspectral images according to a wide variety of observational and surface situations. In this document, we present its characteristics with full details. In its present state of development, the system allows the analysis of spectrophotometric and hyperspectral data by a sequence of controlled direct modeling of the observed spectra, or by their classification from a base of synthetic reference spectra. Spectrophotometry and hyperspectral imaging, thanks to the use of numerical analyzing tools, are very suitable for the study of the chemically varied ices (H2O, CO2, SO2, N2, etc...), which cover more or less extensively most of the evolved satellites and planets. These solids are involved in many phenomena which significantly determine the appearance and the evolution of the planetary systems. An important chapter of this thesis is dedicated to the study of three planetary bodies where, continuously, icy volatiles condense, change and sublimate on the surface: the SO2 ice for the Galilean satellite Io, a molecular mixture of nitrogen, methane, and carbon monoxide for the satellite of Neptune Triton and the planet Pluto. An hyperspectral image of Io acquired by the imaging spectrometer NIMS (Near Infrared Mapping Spectrometer; GALILEO Mission) and two spectrophotometric curves measured by the UKIRT Telescope (United Kingdom Infrared Telescope, Mauna Kea Hawaii), are analyzed thanks to our simulation tool. The obtained results contribute to the improvement of the knowledge dealing with the nature, the composition, and the spatial as well as the vertical distribution of the involved icy deposits.
Keywords
spectroscopy, numerical model, radiative transfer simulation, bidirectional reflectance spectra, BRDF, scattering coefficients, visible, near-IR, ice, N2, CH4, CO, CO2, SO2, surface, Triton, Pluto, Io, Galileo - NIMS, UKIRT - CGS4
Content
instrument-technique, spectral data, BRDF data, planetary sciences, earth sciences, spectral data use
Document type
phd thesis
Year
1998
Pages
1 - 280
Pages number
280
Editor
LGGE
Publisher
Université Joseph Fourier
Publisher city
Grenoble, France
Publication state
published
Identifiers
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Publications