A model of variability in Titan's atmospheric structure

• We compile Cassini–Huygens atmospheric data into a single description.
• Generate an empirical model of mass densities and temperatures.
• This model characterizes the expected atmospheric mass density variations.
• Directly applicable to planning future missions to Titan.
• Will aid planning entry, descent, and landing technology development.

Titan's atmosphere has been extensively studied during the Cassini–Huygens Mission. The polar environment undergoes considerable seasonal variation and is distinct from the more quiescent equatorial environment experienced by the Huygens probe in 2005. The thermal structure of the upper atmosphere is affected by interaction of Titan's atmosphere with the plasma and energetic particles in Saturn's magnetosphere or in the solar wind. Titan's polar regions, and its hydrocarbon lakes in particular, are of interest for future exploration as is the complex organic chemistry that takes place in the upper atmosphere. Thus, specific environmental models are required for future exploration. Furthermore, the models developed to support the design of Huygens had to accommodate wide uncertainties, requiring large design margins. The extensive observations by the Cassini spacecraft (and indeed Huygens itself) provide a basis for narrowing these uncertainties, notably in composition. We provide a description of these new data sets, their scientific basis, and present limitations. The empirically constrained neutral temperatures and densities presented here also have important implications for fundamental chemical modeling. The empirical modeling presented here provides constraints on these models, which will lead to improved estimations of chemical products. Therefore, the paper describes a new model of Titan's atmospheric structure to guide both scientific studies and future engineering studies of exploration of the Saturn system. Of particular interest are aero-capture and aero-braking missions that may enable future exploration of the Saturnian satellite system.