Saturns usually slowly evolutive seasonal cycle has been disrupted in December 2010 between 20N and 50N by the outbreak of an unexpected huge storm system. First Cassini/CIRS and ground-based observations have shown that temperatures, winds and chemistry have been rapidly affected by the storm in the stratosphere. For instance, a temperature increase of 50K over 60 in longitude has been measured by Cassini/CIRS in May 2011.We propose to take advantage of this rare opportunity to use Herschels mapping capability with HIFI and PACS to probe the vertical structure of this unique storm and derive constraints on its formation processes. We will map the emission of H2O at 66 and 67 microns and CH4 at 120 microns and 1882 GHz to measure the temperature between 0.1 and 100 mbar in the stratosphere and to check for any disturbance in the H2O vertical profile. Such disturbance would be due to the injection of massive amounts of tropospheric H2O into the stratosphere by the storm.Because this storm seem to undergo a slow evolution, we propose to monitor its temporal evolution by observing the proposed set of maps once in each of the three remaining observability windows of Saturn.
Herschel was launched on 14 May 2009! It is the fourth cornerstone mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
European Space Agency, cavalie et al., 2013, 'Probing the temperature and chemistry of Saturn's storm with Herschel', SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-9s3r44f
