Goals and/or objectives: our aim is to characterize and better understand the varieties of vertical structure and composition of cloud particles, as well as variations in gas mixing ratios, associated…

This is a $465,093 grant awarded by the National Aeronautics and Space Administration (NASA) to the University of Wisconsin System to support research on characterizing the vertical structure and composition of cloud particles associated with storm systems and features on Saturn. The research aims to enhance understanding of the dynamics of Saturn's polar vortices and the aftermath of the Great Storm of 2010-2011. The work will utilize data from the Cassini mission's Visible and Infrared Mapping Spectrometer (VIMS) and Imaging Science Subsystem (ISS) instruments to analyze cloud properties and gas mixing ratios. This grant is part of NASA's Cassini Data Analysis Program (CDAP), which seeks to maximize the scientific return from the Cassini mission. The contract does not have a set-aside designation.

Goals and/or objectives: our aim is to characterize and better understand the varieties of vertical structure and composition of cloud particles, as well as variations in gas mixing ratios, associated with storm systems and unusual discrete features on saturn, with special focus on the eyes and surroundings of north and south polar vortices and the aftermath of the great storm of 2010-2011. We hope to thus provide a foundation for better understanding of the dynamics of these regions. Approach and methodology: we propose to use vims visible and near-IR spectral imaging observations in combination with ISS imaging, combining reflected solar and 5-micron emission to constrain upper and lower components of cloud structure and composition, using accurate radiation transfer calculations in combination with a non-linear levenberg-marquardt fitting routine. We will use vims near-IR observations to probe the unique spectral features of potential cloud condensates in the 3-\MUM region to identify the mix of materials making up cloud particles in the polar regions, many of which provide spectral evidence of 3-micron absorbing materials, previously only identified in the great storm of 2010-2011 and in storm alley (32-40 DEG s). Extending our analysis from near-IR to visible wavelengths will better constrain the properties of saturn's top visible cloud layer, which is currently of unknown composition. We will use the strong phosphine absorption at 4.3 microns, in combination with weaker absorption features in the 4.8 to 5 micron regions and at 2.9 microns to better define the spatial variation in the vertical profile of phosphine, an indicator of vertical transport. We will use the ISS observations to characterize vertical structure of the eye regions at high spatial resolutions, including 20-KM/pixel coverage of the south polar region and 2 KM/pixel and 4 KM/pixel coverage in the north polar region. Vims spectral observations at spatial resolution of 90 KM/pixel to several hundred KM/pixel will be used to map composition of larger features, which already indicate large spectral differences in the 3-micron region in the north polar region between 2013 and 2016, which may be due to temporal changes. Reasons why proposal is within scope of program element and why program element is the most appropriate for proposed work: the proposed analysis would use cassini observations to enhance understanding of saturn s cloud structure and composition. The proposed effort relies exclusively on cassini observations of saturn and satisfies the cdap program objective to enhance the scientific return of the