Cassini Radio Occultation Observations of Titan's ionosphere: The Complete Set of Electron Density Profiles

Titan's ionosphere is an important component of the moon's environment. Ionospheric densities above approximate to 900 km have been studied with in situ measurements, but few density profiles for lower altitudes has been reported. Here we report the generation of the complete set of twenty ionospheric electron density profiles from the Cassini Radio Science Subsystem instrument, including seven profiles not previously reported (inbound and outbound profiles for flybys T101, T102, and T117 and outbound profile for flyby T119). Uncertainties on average electron density profiles are generally 100-250 cm(-3). On the whole, the main features of the new profiles are generally consistent with previous studies. Specifically, a single layer of plasma with peak density of 1,000-3,000 cm(-3), peak altitude of 1,000-1,300 km, and full-width at half maximum of a few hundred kilometers. Two new profiles are disturbed similar to three identified by previous studies. Based on inspection of the underlying individual profiles, which generally come from two ground stations on opposite sides of Earth, disturbed terrestrial ionospheric conditions are not responsible for the disturbed nature of these Titan ionospheric profiles. A significant plasma layer is present at 500-700 km in several profiles. This low-altitude plasma layer can occur in profiles that are not disturbed.