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Speckle imaging of Titan at 2 microns: surface albedo, haze optical depth, and tropospheric clouds 1996-1998 |
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| Authors: | SG Gibbard B Macintosh CE Max I de Pater AM Ghez CP McKay |
| Institution: | a Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA b Center for Adaptive Optics, University of California at Santa Cruz, Santa Cruz, CA 95064, USA c Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720, USA d Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA e Department of Physics, University of California at Los Angeles, Los Angeles, CA 90095, USA f Southwest Research Institute, Boulder, CO 80302, USA g NASA Ames Research Center, Moffett Field, Mountain View, CA 94035, USA |
| Abstract: | We present results from 14 nights of observations of Titan in 1996-1998 using near-infrared (centered at 2.1 microns) speckle imaging at the 10-meter W.M. Keck Telescope. The observations have a spatial resolution of 0.06 arcseconds. We detect bright clouds on three days in October 1998, with a brightness about 0.5% of the brightness of Titan. Using a 16-stream radiative transfer model (DISORT) to model the central equatorial longitude of each image, we construct a suite of surface albedo models parameterized by the optical depth of Titan's hydrocarbon haze layer. From this we conclude that Titan's equatorial surface albedo has plausible values in the range of 0-0.20. Titan's minimum haze optical depth cannot be constrained from this modeling, but an upper limit of 0.3 at this wavelength range is found. More accurate determination of Titan's surface albedo and haze optical depth, especially at higher latitudes, will require a model that fully considers the 3-dimensional nature of Titan's atmosphere. |
| Keywords: | Titan Infrared observations Surfaces satellite |
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