Revised Near-Infrared Geometric and Surface Albedos of Titan
B. Han, T. Owen (Institute for Astronomy), C. McKay, E. Young (NASA Ames Research Center)
The opacity of Titan's atmosphere in the near-infrared is dominated
by methane absorption, with the exception of a few narrow wavelengths
where the absorption is small enough that we can probe the surface and
lower atmosphere of Titan. The values in the literature for
geometric and surface albedos of Titan
in these methane absorption windows vary greatly
(nearly an order of magnitude at 2 microns),
which makes comparison and integration of the various datasets difficult at best.
We present new geometric and surface albedos in the near-infrared
windows at 1.1, 1.3, 1.6, and 2.0 microns based upon datasets
obtained using the KSPEC medium resolution spectrograph at the
University of Hawaii 2.2 meter telescope at Mauna Kea. The geometric
albedos were calculated using a self-calibration technique
utilizing the simulanteous spectroscopic and K-band imaging capabilities
of KSPEC and did not rely upon matching albedos in the methane
absorption bands with existing published spectra
(such as Fink and Larson's Titan spectra).
This calibration method reduces the uncertainties
due to slit misalignment and tracking errors common to spectroscopic
observations. Surface albedo values derived using atmospheric models
of C. McKay are discussed and their possible implications for Titan's
This work has been supported by NASA grant JPL-959217.