Surface of Titan : model and VIMS observations

The Huygens probe has allowed to describe the atmosphere and the surface of Titan in detail. To date, the surface reflectivity as observed by DISR is not fully understood.In this work, we first propose a model of the surface reflectivity made of a layer of ice covered by a layer of fluffy aerosols. This well explains the observed surface reflectivity by DISR, with a reflectivity having a maximum (peak) at 750 nm and a blue slope at longer wavelength and a red slope at shorter wavelength. Our model essentially relies on our ability to model the radiative transfer inside the continuous layer of aerosol sedimented at the surface. However, we also find a shift in the reflectivity peak between the surface reflectivity as observed by DISR and the results obtained when using the aerosol refractive index of airborne aerosols. We propose an explanation for this effect.The second part of the work consists in checking the data. We find that this shift in the reflectivity peak also exits in the data. Using a model of radiative transfer, with a description of the atmosphere properties derived from analysis made by Huygens instruments, we are able to reproduce the intensity observed by VIMS, and we can retrieve the surface albedo. We essentially focus on the aera around Huygens landing site, and we characterize the differences between the bright and dark zones.