Vertical structure mapping of Saturn's 2011 giant vortex by means of Cassini VIMS-V data analysis.

A giant storm has erupted at Saturn's North hemisphere in December 2010. The storm has grown by enveloping a region extended over an entire parallel of the hemisphere, until the outburst exhausted in July 2011 [7,14]. Among the effects of the storm, that produced strong perturbations to stratospheric temperatures [7], a giant tropospheric vortex has formed in the storm wake in December, measuring in January 11000 by 12000 km, in the north-south and east-west directions respectively [14]. Starting from May 2011, the vortex has been imaged several times by the Visual and Infrared Mapping Spectrometer (VIMS) [4] on board of the Cassini spacecraft. In this work, the data registered on 24/08/2011 by the visual channel of the spectrometer (VIMS-V), operating between 350 nm and 1050 nm with a 7.3 nm spectral sampling, have been analyzed. An inversion method has been developed based on the Bayesian approach and taking advantage of the Gauss-Newton method to minimize the cost function [12]. This method has been used to study the clouds and hazes vertical structure above the vortex region, to retrieve the microphysical and geometrical properties of the decks. For each layer the top pressures have been retrieved, along with the related total number densities and effective radii. 2D spatial maps for each of those parameters have been produced.