6596 20240122122233.0 CTALK-2024-0008 Coyette, A. Cassini States of Ganymede and Callisto 2023 2023-07-07 Like our Moon, the large icy satellites of Jupiter are thought to be in a Cassini State, an equilibrium rotation state characterized by a synchronous rotation rate and a precession rate of the rotation axis equal to that of the normal to the orbit. In these equilibrium states (up to four Cassini States are possible for a solid and rigid satellite), the spin axis of the satellite, the normal to its orbit and the normal to the inertial plane remain coplanar with an obliquity that remains theoretically constant. However, as the gravitational torque exerted on the satellite shows small periodic variations, the orientation of the rotation axis will also vary with time and nutations in obliquity will appear. Here we present the influence of the triaxiality and of the presence of a subsurface ocean on the Cassini States of Ganymede and Callisto and assess the possibility of determining whether a future observation of the obliquity of Ganymede or Callisto by the JUICE Mission could constrain the interior structure of these satellites. 3PRODPLANINT/ 3PRODPLANINT/ 3PRODPLANINT NO Ganymede Callisto Baland, R.-M. Van Hoolst, T. Complex Planetary Systems II Kavli-IAU Symposium 382, Namur, Belgium rose-marie.baland@ksb-orb.be https://cpsii.unamur.be/ Contributed CTALKCONT