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[22.04] Cassini/CIRS Observations of Titan's Equatorial Region in the Submillimeter Spectral Range

B. Bézard, A. Coustenis, T. Fouchet, E. Lellouch (Obs. Paris-Meudon), B. Conrath (Cornell U.), R. Achterberg (SSAI), D. Jennings, M. Flasar (NASA/GSFC), CIRS Investigation Team

On July 2--3, 2004 UT, the Composite Infrared Spectrometer (CIRS) aboard Cassini recorded spectra of Titan's equatorial latitudes (13S--2N) with a spectral resolution of 0.26 cm^-1 (unapodized). We present here the analysis of the average spectrum recorded by the far infrared spectrometer (FP1), covering 10 to 600 cm^-1 and corresponding to a total integration time of 4.7 hours. This spectrum shows rotational lines from CO, HCN ,CH₄, and possibly H₂O. Mean stratospheric abundances of these species have been derived using temperature information from the collision--induced continuum in the FP1 and the 7.7--\mum \nu₄ band of methane recorded by the mid-infrared spectrometer in FP4. In particular, analyzing simultaneously the \nu₄ band and the rotational lines, prominent in the 70--140 cm^-1 range, allows us in principle to disentangle the methane mixing ratio and the temperature profile in the stratosphere, the two components affecting differently the emission observed in the two spectral regions.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.