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D. Luz, R. Courtin, D. Gautier (Paris-Meudon Observatory, LESIA, France), F. Ferri (CNES, France), T. Appourchaux, J.-P. Lebreton (ESA, ESTEC, The Netherlands), M. Cabane, P. Rannou (Service d'Aeronomie, Univ. Paris 6, France), F. Hourdin (Laboratoire de Meteorologie Dynamique, Paris, France), L. Lara (Instituto de Astrofisica de Andalucia, Granada , Spain), A. Kaufer (ESO, Paranal, Chile)
We will report on recent efforts to characterize the zonal wind flow in Titan's stratosphere. We used the UVES echelle spectrometer at the focus of the UT2 of the Very Large Telescope at Paranal, Chile, to measure the reflection spectrum of Titan between 4200 and 6200 angstrom with a resolution of ~80,000. The purpose of these observations, which were carried out in February 2002, is to detect the differential Doppler shift induced by the zonal wind flow between the East and West limbs of Titan. However, because the wind speed is not expected to exceed 200 m/s, an absolute detection of the Doppler shift on isolated solar lines is not feasible, even at the spectral resolution of UVES. Therefore, we have made use of a retrieval scheme developed for absolute stellar accelerometry (Connes 1985, ApSS 110, 211; Martic et al. 1999, A&A 351, 993) to extract the velocity signal by simultaneously taking into account all the lines present in the spectrum. We will describe the method and discuss preliminary results.
Research supported by the "Programme National de Planetologie" of the Institut National des Sciences de l'Univers (France). D. Luz acknowledges financial support by the Portuguese Foundation for Science and Technology, ref.SFRH-BPD-3630-2000.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.