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T. Kostiuk, K. E. Fast (NASA GSFC), T. A. Livengood (Challenger Ctr.), F. Schmülling (U. Cologne), T. Hewagama (U MD), D. Buhl, P. Romani (NASA GSFC), H. U. Kaufl (ESO)
We report on an ongoing study of ethane abundance and stratospheric thermal structure on Saturn using ultra-high resolution infrared heterodyne spectroscopy with resolving power of 1,000,000. Data consist of line emission spectra of ethane near 12 microns taken at the NASA IRTF from 1989 to 1999 and broadband spectral images taken in 1996 with TIMMI at the European Southern Observatory 3.6-m telescope. The high spectral resolution permits constraints on both ethane abundance and stratospheric temperature. Rough meridional distribution is obtained from globally distributed line measurements as well as from the spectral imaging data. Temporal changes are observed over the 11-year period corresponding to one-third of Saturn’s year. Significant difference in the spectral features is observed in mid-summer high North latitudes and mid-Spring high South latitudes. A warmer temperature and a lower ethane abundance were retrieved from the southern measurements. The retrieved abundances and thermal profiles will be presented and possible causes of the changes will be discussed. Results will be complementary to expected data that will be acquired by the Composite Infrared Spectrometer, CIRS, on the Cassini spacecraft starting in 2004.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.