Global mapping of Titan's surface using an empirical processing method for the atmospheric and photometric correction of Cassini/VIMS images

摘要

We have processed all images of Titan's surface acquired by the Visual and Infrared Mapping Spectrometer between 2004 and 2010, with the objective of producing seamless global mosaics of the surface in the six infrared atmospheric windows at 1.08, 1.27, 1.59, 2.03, 2.6-2.7 and 5 μm. A systematic study of the photometry at 5 urn, where haze scattering can be neglected, shows that the surface behaves to first order like a Lambert surface. The results at 5 um are generalized to lower wavelengths, adding an empirical correction accounting for scattering from atmospheric aerosols, using methane band wings as a proxy for the calculation of the scattering additive term. Mosaics incorporating this empirical correction for the geometry and haze scattering show significantly less seams than any previous maps integrating data acquired over such a wide range of observing geometries, and may therefore be used for the study of surface properties. We provide several suggestions for further studies aimed at improving the global mapping of the surface of Titan. With the considered thresholds limits on the acquisition parameters, we found that 13% of Titan's surface has been mapped at an instrument resolution better than 10 km/pixel, 56% of the surface was seen at a resolution between 10 and 20 km/pixel, and 24% of the coverage falls in the range 20-50 km/pixel.