Spectroscopic observations of Jupiter and Saturn are here reported to show
the possible applications to the future data acquired by the instrument VIM
S (Visible and Infrared Mapping Spectrometer) on board of the Cassini Missi
on. The following images and spectra have been acquired by a similar instru
ment called VNIR (Visible and Near Infrared Spectrometer) during several ob
servational campaigns. We put our attention on the distribution of the meth
ane in the visible and infrared wavelengths since it is the main absorber i
n the atmosphere of Jupiter and Saturn in this wavelength range We have stu
died the ratio between the CH, equivalent width and the integral of the abs
orption coefficient of methane at different wavelengths.
This kind of study permits to obtain many indications about the vertical di
stribution of methane and about the vertical structure of the planetary atm
osphere. Classical questions when studying planetary atmospheres are the ve
rtical temperature-pressure profiles, composition, structure and dynamics.
Usually these questions are addressed with a medium to high resolution spec
trometer. Imaging spectroscopy permits to put together at the same time bot
h spatial and spectral information and its use allows us to resolve some of
the above-mentioned questions such as identification of main atmospheric c
omponents, vertical analysis of the atmosphere, spectral analysis of clouds
and vortices and determination of global wind pattern. (C) 1998 Elsevier S
cience Ltd. All rights reserved.