  Among the lines of evidence for a buried ocean on Titan is the possible
detection, in 2005, by the Permittivity, Wave and Altimetry (PWA) analyzer on
board the ESA Huygens probe of Schumann-like Resonances (SR). SR are Extremely
Low Frequency electromagnetic waves resonating between two electrically
conductive layers. On Titan, it has been proposed that they propagate between
the moon's ionosphere and a salty subsurface water ocean. Their
characterization by electric field sensors can provide constraints on Titan's
cavity characteristics and in particular on the depth of Titan's ocean which is
key to better assess Titan's habitability. For this work we have developed a
numerical model of Titan's electromagnetic cavity as well as a surrogate model
to conduct simulations and sensitivity analyses at a low computational cost.
This surrogate model is used both to re-assess PWA/Huygens measurements and to
predict the future performance of the EFIELD experiment on board the NASA
Dragonfly mission. We demonstrate that the PWA/Huygens measurements, in
particular due to their low spectral resolution, do not bring any meaningful
constraint on Titan's ocean depth. On the other hand, the finer resolution of
the EFIELD experiment and its ability to capture several harmonics of SR should
provide more robust constraints on Titan's internal structure, especially if
the electrical properties of the ice crust and the atmosphere can be better
constrained.
