The tidal response of Ganymede and Callisto with and without liquid water oceans

Calculations of the tidal responses of Ganymede and Callisto reveal that tidal amplitudes on these bodies may be as large as a few meters if a liquid ocean exists to decouple the surface ice from the interior. Tides on Ganymedeʹs surface can exceed 7 m peak-to-peak variation, while on Callisto the tidal amplitude can exceed 5 m in the presence of a liquid ocean. Without an ocean, tidal amplitudes are less than 0.5 m on Ganymede and less than 0.3 m on Callisto. An orbiting spacecraft using an altimeter for crossover analysis and Doppler tracking from Earth should be able to achieve sufficient accuracy to identify the tidal amplitude to within about a meter over the course of a few months (observing tens of tidal cycles).