The case for future gravity science investigations at Saturn with a planetary orbiter

The next phase in the robotic exploration of the Saturnian system will target unresolved questions 6 about the gas giant’s atmosphere, interior, magnetosphere and rings that were left open by investiga7 tions onboard the Cassini mission. Among these, we find gravity science objectives, which relate mainly 8 to explaining the origin of the large wind-induced gravity signal and reconciling existing incongruities 9 regarding the internal density distribution. Here we attempt at identifying which future observations 10 may yield additional information about Saturn’s internal mechanisms. We report on the results of pre11 cise numerical simulations for gravity science experiments carried out with a planetary orbiter 12 and characterized by varying periapsis altitude over the 1-bar planetary surface. The goal 13 is to identify achievable measurement requirements that can advance the current understanding of 14 Saturn’s interior and atmospheric dynamics. We find that inclined, elliptical orbits with low-altitude 15 closest approaches over the northern hemispheres can improve over the present determination 16 of the gravity field coefficients by up to one order of magnitude, provided that at least a dozen 17 pericenters are devoted to gravity science. Furthermore, if these observations are combined 18 with the available Cassini Grand Finale data in the southern hemisphere, a significant 19 improvement in terms of maximum measurable gravity field degree is observed.