a b s t r a c tWe describe a concept for an instrument to measure the thickness of the ice shell on a planetary body such as Jupiter's moon Europa. Unlike a high powered and massive device such as an ice-penetrating radar, the instrument would be a passive receiver of a naturally occurring signal generated by interactions of deep penetrating cosmic ray neutrinos. We discuss the basic concept and consider the instrument design requirements from the perspective of a NASA Outer Planet Orbiter Mission. We show results of simulations, compare signal-to-noise estimates, and examine possible components and configurations for the antenna, receiver, and electronics. We note some options that can be used to reduce mass and power. Finally, we present a list of issues that would need further study to produce a more concrete design.