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R. Moreno (IRAM), A. Marten (LESIA, Obs. Paris)
Narrow emission lines of HC3N (cyanoacetylene) and CH3CN (acetonitrile) were observed on Titan with the Plateau-de-Bure Interferometer of IRAM (France) in February-March 2003. Using the most extended configuration of the six-antenna array, an angular resolution of 0.6 arc sec was obtained at the working frequencies (227.4 and 220.7 GHz, respectively), permitting a disk-resolved investigation of the nitrile composition and the zonal wind flow in the upper atmosphere.
Observing details and composition results are reported in an accompanying presentation (Marten and Moreno, BAAS, 2003). Our second objective was reached by recording the spectra at a very high spectral resolution of 40 kHz. A sufficient signal-to-noise ratio (greater than 10 for the equatorial measurements) was achieved after 8 hours of integration time on Titan.
Examination of the contribution functions calculated for the strongest lines used in our analysis shows that the probed altitudes are in the low mesosphere around 400 km (0.01-mbar pressure level).
The Doppler shifts of the lines measured between the east and west limbs provide evidence for a prograde wind direction. The retrieved maps focusing on the zonal wind speeds determined across Titan's disk will be presented.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.