Geometry of the Saturn system from the 3 July 1989 occultation of 28 Sgr and Voyager observations

The pole direction and radius scale for the ring system of Saturn are presently determined by combining the July 3, 1989 observations of 28 Sgr's occultation by Saturn with Voyager 1 and 2 photopolarimeter occultation measurements. The computation of ring-orbit models is separately conducted via a sky-plane method and a solar system barycentric vector approach; the results obtained by both methods are in excellent agreement. If Voyager trajectory uncertainties are assumed to be negligible, these observations can be used to determine the precession rate of the pole of Saturn about the solar system's invariable pole.