Advanced calibration of fourier-transform spectrometers

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Remote sensing applications require as much information as possible in order to maximize the identification of scene characteristics. In order to do so, basic approaches include processing of images (giving spatial details in two dimensions) and spectra (giving spectral details, which are the repartition of the energy across many distinct "colours", corresponding to narrow optical bands). Nowadays instruments are developed to provide simultaneously spatial and spectral information. They are called hyperspectral imagers or imaging spectrometers. Such instruments provide spectra for each pixel, conversely images for each spectral band, resulting therefore in three-dimensional data cubes (representing eventually huge amount of data).      Ideal data cubes would contain only scene information, without any instrument artefacts. However, instrument contributions are always merged with scene characteristics in the measured data. One has thus to develop approaches to remove, as completely as possible, the instrument contributions for every point in the data cube. This process is called calibration. It is a tremendous task to properly calibrate large data cubes.      The aim of the proposed research is to study a particular imaging spectrometer, the Fourier-transform spectrometer. We plan to precisely predict its behaviour by using the instrument spectral response function, which is related to its gain and its line shape. We will next develop accurate methods to calibrate data produced by imaging Fourier-transform spectrometers based on gain and line shape knowledge. Laboratory imaging Fourier-transform spectrometers will be used to test theoretical predictions. Within our research program, we will also develop numerically efficient ways to implement the proposed calibration algorithms.      Our studies are thus oriented towards the realisation of more efficient and reliable instruments thanks to better understanding of their fundamental behaviour. Such optimised instruments become the key component in critical ground, flight and space projects, aiming for civil as well as defence applications. Our goal is therefore to develop novel instruments showing improved performances for lower cost / mass / volume.