Titan’s 2 Mm surface albedo and haze optical depth in 1996--2004

[1] We observed Titan in 1996–2004 with high-resolution 2 mm speckle and adaptive optics imaging at the W. M. Keck Observatory. By observing in a 2 mm broadband filter we obtain images that have contributions from both Titan’s surface and atmosphere. We have modeled Titan’s atmosphere using a plane-parallel radiative transfer code that has been corrected to agree with 3-D Monte Carlo predictions. We find that Titan’s surface albedo ranges from 0.02 in the darkest equatorial region of the trailing hemisphere to ’0.1 in the brightest areas of the leading hemisphere. Over the past quarter of a Saturnian year haze optical depth in Titan’s Southern hemisphere has decreased substantially from a value of 0.48 in 1996 down to 0.18 in 2004, while the northern haze has been increasing over the past few years. As a result of these changes, in 2004 the North/South haze asymmetry at K’ band has disappeared.