loading page

Regional mapping of aerosol population and surface albedo of Titan by the massive inversion of the Cassini/VIMS dataset
  • +7
  • Sebastien Rodriguez,
  • Maël Es-Sayeh,
  • Thomas Cornet,
  • Luca Maltagliati,
  • Thomas Appéré,
  • Pascal Rannou,
  • Stephane Le Mouelic,
  • Christophe Sotin,
  • Jason Barnes,
  • Robert Brown
Sebastien Rodriguez
Institut de Physique du Globe de Paris

Corresponding Author:[email protected]

Author Profile
Maël Es-Sayeh
University of Oxford
Author Profile
Thomas Cornet
Author Profile
Luca Maltagliati
Nature Astronomy, Springer Nature
Author Profile
Thomas Appéré
IPAG Institut de Planétologie et d’Astrophysique de Grenoble
Author Profile
Pascal Rannou
GSMA - UUniversity of Reims Champagne-Ardennes
Author Profile
Stephane Le Mouelic
LPG Nantes, UMR 6112, CNRS, OSUNA, Université de Nantes
Author Profile
Christophe Sotin
Jet Propulsion Laboratory-California Institute of Technology
Author Profile
Jason Barnes
University of Idaho
Author Profile
Robert Brown
Univ Arizona
Author Profile


Mapping Titan’s surface albedo is a necessary step to give reliable constraints on its composition. However, even after the end of the Cassini mission, surface albedo maps of Titan, especially over large regions, are still very rare, the surface windows being strongly affected by atmospheric contributions (absorption, scattering). A full radiative transfer model is an essential tool to remove these effects, but too time-consuming to treat systematically the ~50000 hyperspectral images VIMS acquired since the beginning of the mission. We developed a massive inversion of VIMS data based on lookup tables computed from a state-of-the-art radiative transfer model in pseudo-spherical geometry, updated with new aerosol properties coming from our analysis of observations acquired recently by VIMS (solar occultations and emission phase curves). Once the physical properties of gases, aerosols and surface are fixed, the lookup tables are built for the remaining free parameters: the incidence, emergence and azimuth angles, given by navigation; and two products (the aerosol opacity and the surface albedo at all wavelengths). The lookup table grid was carefully selected after thorough testing. The data inversion on these pre-computed spectra (opportunely interpolated) is more than 1000 times faster than recalling the full radiative transfer at each minimization step. We present here the results from selected flybys. We invert mosaics composed by couples of flybys observing the same area at two different times. The composite albedo maps do not show significant discontinuities in any of the surface windows, suggesting a robust correction of the effects of the geometry (and thus the aerosols) on the observations. Maps of aerosol and albedo uncertainties are also provided, along with absolute errors. We are thus able to provide reliable surface albedo maps at pixel scale for entire regions of Titan and for the whole VIMS spectral range.