Radar Travel Time Tomography for Subsurface Ice Exploration at Saturn's Moon Enceladus

We present an iterative travel time inversion approach for mapping the subsurface permittivity distribution within the ice crust of Saturn's moon Enceladus utilizing bistatic transmission lines between an orbital radar and an active target (transponder) located in the ice. The approach builds on the dependence between the measured radar travel times and the underlying permittivity distribution. The estimated permittivity distribution can then be used to infer physical parameters of the Enceladus ice crust such as density, temperature, and grain size. Building on the same rationale, we furthermore suggest an effective localization strategy for targets located in the ice crust. Both permittivity distribution estimate and localization show promising results when tested on synthetic data.