Saturn's Internal Structure - What Can be Learned from Cassini's Proximal Orbits

The Cassini spacecraft has been orbiting Saturn since July, 2004. After unprecedented success exploring the Saturnian system, the Cassini Mission is planned to end in September, 2017. The ultimate fate of the spacecraft must prevent contamination of sensitive environments, such as Titan or the Saturnian moons. One potential end-of-mission scenario being considered is to place the spacecraft on a trajectory to impact Saturn's atmosphere. Leading up to Saturn impact, between November, 2016 and September, 2017, the spacecraft would execute forty-two short-period orbits, 20 orbits with a 7.2 day period and periapses at 2.5 Saturn radii, just outside Saturn's F-ring, followed by twenty-two highly inclined (63.4 degree), orbits with a period of 6.2 days and periapses just above Saturn's atmosphere in the gap between the planet and the inner edge of the D-ring. One of the highest priority goals on these final unique proximal orbits is to probe Saturn's interior structure, based on measurements of its gravity and magnetic fields. We present characteristics of these orbits of relevance for analysis and understanding Saturn's internal structure.