The Cassini VIMS archive of Titan: from browse products to global infrared color maps

TL;DR

This study compiles and processes the entire VIMS dataset of Titan to create global infrared color maps, overcoming atmospheric effects and providing new insights into surface spectral variability.

Contribution

It presents a comprehensive global mapping of Titan's surface using VIMS data, with novel atmospheric correction techniques and publicly available multispectral products.

Findings

Created a global infrared color map of Titan's surface.

Identified spectral variability and surface features such as dunes and craters.

Developed methods to mitigate atmospheric effects in spectral data.

Abstract

We have analyzed the complete Visual and Infrared Mapping Spectrometer (VIMS) data archive of Titan. Our objective is to build global surface cartographic products, by combining all the data gathered during the 127 targeted flybys of Titan into synthetic global maps interpolated on a grid at 32 pixels per degree (~1.4 km/pixel at the equator), in seven infrared spectral atmospheric windows. Multispectral summary images have been computed for each single VIMS cube in order to rapidly identify their scientific content and assess their quality. These summary images are made available to the community on a public website (vims.univ-nantes.fr). The global mapping work faced several challenges due to the strong absorbing and scattering effects of the atmosphere coupled to the changing observing conditions linked to the orbital tour of the Cassini mission. We determined a surface photometric function which accounts for variations in incidence, emergence and phase angles, and which is able to mitigate brightness variations linked to the viewing geometry of the flybys. The atmospheric contribution has been reduced using the subtraction of the methane absorption band wings, considered as proxies for atmospheric haze scattering. We present a new global three color composite map of band ratios (red: 1.59/1.27 {\mu}m; green: 2.03/1.27 {\mu}m; blue: 1.27/1.08 {\mu}m), which has also been empirically corrected from an airmass (the solar photon path length through the atmosphere) dependence. This map provides a detailed global color view of Titan's surface partially corrected from the atmosphere and gives a global insight of the spectral variability, with the equatorial dunes fields appearing in brownish tones, and several occurrences of bluish tones localized in areas such as Sinlap, Menvra and Selk craters. (...)