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A. Coustenis, E. Gendron (DESPA, Paris Observatory, France), O. Lai (C.F.H.T., Hawaii), J.-P. Veran (H.I.A., National Research Council, Victoria, Canada), M. Combes (DESPA, Paris Observatory)
We have obtained observations of Titan using the PUEO adaptive optics system of the CFHT (Hawaii), on October 27th, 1998, when Titan was at Greatest Eastern Elongation with respect to Saturn. The images were acquired using narrow-band filters in the J and H bands, in the centers of the methane atmospheric windows (at 1.29 and 1.60 \mum respectively, filters J1 and H1) and in the wings of the CH4 bands (at 1.18 and 1.64 \mum respectively, filters J2 and H2). To our knowledge, these are the first images of Titan at 1.3 \mum.
The seeing during this run was exceptionally good (on the order of 0.3 arcsec for the best part of the night). As a consequence, the retrieved PSFs afford a Strehl ratio of about 50% in H and 35% in J, for FWHMs of about 0.1 and 0.08 arcsec, respectively. From these, we have reconstructed the PSFs corresponding to each Titan observation and proceeded to deconvolve our images. The deconvolution process is very efficient in this case. The images taken in the J2 and H2 filters allow us to probe the atmosphere of Titan and clearly show a bright South Pole, with emphasis to the Eastern limb. We use them to eliminate the atmospheric contribution from the J1 and H1 images. The latter both show an additional bright feature near the equator, with a contrast of about 40% in H and 35% in J. Careful measurements of a standard star during our observations should allow us to apply photometric evaluations of these morphological structures on Titan.
We will present the results of the analysis of our observations and discuss the inferred implications on the nature of Titan's surface.
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The author(s) of this abstract have provided an email address for comments about the abstract: coustenis@obspm.fr