The Global Shape, Gravity Field, and Libration of Enceladus

In order to improve our understanding of the interior structure of Saturn's small moon Enceladus, we reanalyze radiometric tracking and onboard imaging data acquired by the Cassini spacecraft during close encounters with the moon. We compute the global shape, gravity field, and rotational parameters of Enceladus in a reference frame consistent with the International Astronomical Union's definition, where the center of the Salih crater is located at -5 degrees East longitude. We recover a quadrupole gravity field with J3 and a forced libration amplitude of 0.091 degrees +/- 0.009 degrees (3-sigma). We also compute a global shape model using a stereo-photoclinometry technique with a global resolution of 500 m, although some local maps have higher resolutions ranging from 25 to 100 m. While our overall results are generally consistent with previous studies, we infer a thicker 27-33 km mean ice shell, a thinner 21-26 km mean ocean thickness, and a mean core density range of 2,270-2,330 kg/m3. Geodetic data, such as shape, gravity, and rotation, provide important constraints for probing a planetary body's interior structure. We analyze radiometric tracking and onboard imaging data acquired during close encounters of Enceladus by the Cassini spacecraft to compute geodetic products including topographic and gravitational fields in a common reference frame. The recovered Enceladus topography has a global resolution of 500 m, with some local regions having 25-100 m resolution. Our study suggests that Enceladus has a 27-33 km mean ice shell thickness, a 21-26 km mean ocean thickness, and a mean core density range of 2,270-2,330 kg/m3. A full quadrupole gravity field with J3 and the forced libration amplitude of 0.091 degrees +/- 0.009 degrees are recoveredA 500-m resolution global topography model was computed, with some local regions having 25-100 m resolutionThe results suggest that Enceladus has a 27-33 km mean ice shell thickness, a 21-26 km ocean thickness, and a mean core density range of 2,270-2,330 kg/m3