Atmospheric studies with spectro-imaging : prospects for the vims experiment on Cassini

Abstract

Spectroscopic observations of Jupiter and Saturn are here reported to show the possible applications to the future data acquired by the instrument VIMS ( Visible and Infrared Mapping Spectrometer) on board of the Cassini Mission. The following images and spectra have been acquired by a similar instrument called VNIR ( Visible and Near Infrared Spectrometer) during several observational campaigns. We put our attention on the distribution of the methane in the visible and infrared wavelengths since it is the main absorber in the atmosphere of Jupiter and Saturn in this wavelength range We have studied the ratio between the CH 4 equivalent width and the integral of the absorption coefficient of methane at different wavelengths. This kind of study permits to obtain many indications about the vertical distribution of methane and about the vertical structure of the planetary atmosphere. Classical questions when studying planetary atmospheres are the vertical temperature-pressure profiles, composition, structure and dynamics. Usually these questions are addressed with a medium to high resolution spectrometer. Imaging spectroscopy permits to put together at the same time both spatial and spectral information and its use allows us to resolve some of the above-mentioned questions such as identification of main atmospheric components, vertical analysis of the atmosphere, spectral analysis of clouds and vortices and determination of global wind pattern.