On December 2010 a giant storm erupted in Saturn's North springtime hemisphere. A giant vortex formed in the storm wake and persisted after the principal outburst exhausted on July 2011. The vortex had been imaged several times by the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini probe, starting from May 2011, and it was still present in the December 2012 observations In this work we have analyzed the data recorded by the visual channel of the spectrometer (VIMS-V). VIMS-V operates in the spectral range 350 - 1050 nm with a nominal spectral resolution of 7.3 nm and a nominal angular resolution of 500 murad. Spectral data have been first analyzed by a forward radiative transfer model based on the LibRadtran code, then an inverse model has used to retrieve microphysical and geometrical properties of the clouds overlying the vortex. The forward model relies on the assumptions of a plane parallel atmosphere, multiple scattering, the Mie theory to compute single scattering properties and the molecular scattering adapted to Saturn's atmosphere. The inverse code is based on the optimal estimation technique, it is robust and capable to handle several free parameters at a time. The best fits to the observed radiance spectra are obtained by means of a least square analysis, in which the cost function is minimized taking advantage of the Gauss-Newton method. Applying this procedure, we produced spatial maps for each of the free parameters, including: effective radii for the particles size distributions of each cloud or aerosol deck; total number densities of the particles; and top pressures of each deck. In this work we focused on the data retrieved by VIMS on August 2011. We plan to extend the analysis on data retrieved months later, to map the evolution the parameters undergo in time. The analysis extension to the range 1.0-5.0 micron, covered by the infrared channel of VIMS (VIMS-IR) is also planned.
Vertical structure mapping of Saturn’s 2011 - 2012 giant vortex by means of Cassini VIMS-V data analysis / Oliva, Fabrizio; A., Adriani; M., Moriconi; G., Liberti; E., D'Aversa. - ELETTRONICO. - (2014). (Intervento presentato al convegno Committee on Space Research tenutosi a Mosca nel 2-10/08/2014).
Vertical structure mapping of Saturn’s 2011 - 2012 giant vortex by means of Cassini VIMS-V data analysis.
OLIVA, FABRIZIO;
2014
Abstract
On December 2010 a giant storm erupted in Saturn's North springtime hemisphere. A giant vortex formed in the storm wake and persisted after the principal outburst exhausted on July 2011. The vortex had been imaged several times by the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini probe, starting from May 2011, and it was still present in the December 2012 observations In this work we have analyzed the data recorded by the visual channel of the spectrometer (VIMS-V). VIMS-V operates in the spectral range 350 - 1050 nm with a nominal spectral resolution of 7.3 nm and a nominal angular resolution of 500 murad. Spectral data have been first analyzed by a forward radiative transfer model based on the LibRadtran code, then an inverse model has used to retrieve microphysical and geometrical properties of the clouds overlying the vortex. The forward model relies on the assumptions of a plane parallel atmosphere, multiple scattering, the Mie theory to compute single scattering properties and the molecular scattering adapted to Saturn's atmosphere. The inverse code is based on the optimal estimation technique, it is robust and capable to handle several free parameters at a time. The best fits to the observed radiance spectra are obtained by means of a least square analysis, in which the cost function is minimized taking advantage of the Gauss-Newton method. Applying this procedure, we produced spatial maps for each of the free parameters, including: effective radii for the particles size distributions of each cloud or aerosol deck; total number densities of the particles; and top pressures of each deck. In this work we focused on the data retrieved by VIMS on August 2011. We plan to extend the analysis on data retrieved months later, to map the evolution the parameters undergo in time. The analysis extension to the range 1.0-5.0 micron, covered by the infrared channel of VIMS (VIMS-IR) is also planned.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
