37th DPS Meeting, 4-9 September 2005
Session 51 Titan II
Oral, Thursday, September 8, 2005, 2:00-3:50pm, Music Concert Hall

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[51.01] Analysis of Titan Cassini/CIRS limb spectra from the Tb and T3 flybys: temperature and abundance profiles at 15\circS and 80\circN

S. Vinatier, B. Bézard, T. Fouchet (Observatoire de Paris-Meudon, France), B. J. Conrath (Cornell University, USA), R. K. Achterberg (SSAI, USA), P. N. Romani, F. M. Flasar (NASA/GSFC, USA), CIRS Investigation Team

We present an analysis of Titan's limb spectra obtained by CIRS (Composite InfraRed Spectrometer) during the Tb (December 13, 2004) and T3 (February 14, 2005) flybys. Tb spectra were recorded at equatorial latitudes (15\circS) and T3 spectra near the north pole (80\circN). We mainly focused on limb spectra to retrieve vertically-resolved information on the thermal profile and abundance profiles of some molecules (acetylene, ethane, diacetylene ...). For Tb observations, the viewing altitudes span the range 250 to 470 km, and in T3 they cover the interval 80-475 km. In order to determine abundance profiles, the temperature profile must be known as a first step. It is retrieved from the emission of the \nu4 methane band centered at 1305 cm-1 (7.7 microns), using an inversion algorithm of the transfer equation. For Tb, a set of 8 limb spectra was used (giving information in the 250-480 km range) along with a nadir spectrum giving additional information at lower levels (in the range 200-250 km). In the case of T3, a set of 7 limb spectra was used giving information between 230 and 475 km. Both retrieved thermal profiles clearly show a stratopause, located around 310 km at 15\circS with a temperature of 186 K, and around 390 km with a temperature of 205 K at 80\circN.

The retrieved temperature profiles were then used to model the observed spectra in the range 600-1000 cm-1. We will present the vertical profiles of the gaseous absorbers present in this range as derived from the best fits of the whole set of observed spectra.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.