  In this work, we investigate a minimalist model capable of accurately
replicating the forced librations of an icy moon with a subsurface ocean. The
model holds potential to predict the presence of a subsurface ocean through
analysis of longitudinal librations. We demonstrate that a two-layered model,
with a prestressed icy crust and a fixed mantle cavity, can effectively model
the librational behavior of icy moons. The proposed model is applied to model
the longitudinal libration of Enceladus and Mimas, two medium-sized icy moons
of Saturn.
