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R. K. Achterberg (SSAI), B. J. Conrath (Cornell U.), F. M. Flasar (NASA/GSFC), C. A. Nixon (Univ. of Maryland), CIRS Team
On July 2, 2004, the Cassini spacecraft performed its first Titan flyby, at a range of 340000 kilometers. During this flyby, the Composite Infrared Spectrometer mapped the south polar region, and the Saturn facing sections of the equator and low to mid-southern latitudes, over the spectral range from 600 to 1400 cm-1 (16.7 to 7.1 microns) with an apodised spectral resolution of 2.8 cm-1 and a spatial resolution of 2.5 degrees of great circle arc. We have used data from the methane \nu4 band to retrieve temperatures in the upper stratosphere between .5 and 5 mbar. Except near the equator, the temperatures are nearly axisymmetric, with temperatures near the south pole approximately 4K colder than at the equator. Assuming gradient wind balance, the observed meridional temperature gradients indicate wind speeds of approximately 140 m s-1 near the equator in the upper stratosphere. We also see an extended warm feature, with amplitude of about 2K, centered on the equator about 15 degrees east of the sub-Saturn point. With the limited longitude coverage near the equator in the current dataset, it is unclear if this is an isolated feature, or one maximum from a wave of zonal wavenumber 1 or 2.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.