Very High Resolution IR Imaging of Titan's Surface and Atmosphere

S. Gibbard, B. Macintosh, D. Gavel, C. Max (LLNL), I. de Pater (UC Berkeley), E. Young, C. McKay (NASA Ames)

The ten-meter aperture of the Keck 1 Telescope affords unprecedented spatial resolution (0.04 arc sec at 2.2 microns) if blurring due to atmospheric turbulence can be removed. Here we report on observations of Titan which use speckle imaging to compensate for atmospheric blurring. In the summer of 1996 we observed Titan with the Near Infra-Red Camera (NIRC) in the K' and H bands, achieving very high spatial resolution of 300 km on Titan's surface. Clear surface structure is observed at these scales, at considerably higher contrast and resolution than has previously been reported. We separate atmospheric from surface features by using a radiative transfer model to simulate the absorption, reflection, and scattering of photons in the atmosphere of Titan. We compute the model with our data for overall brightness, north/south asymmetry, and limb brightening. The results from this process are 1) a surface albedo map at K and H band, and 2) values for atmospheric parameters such as haze distribution and vertical atmospheric structure. The surface albedo ranges from nearly zero in the regions near -150 degrees longitude to a peak at 0.15 in the bright feature on the leading hemisphere at 120 degrees longitude. With these extremely encouraging results we plan to re-observe Titan at Keck in June 1997 to obtain additional longitude coverage of the surface.