The occultation of 28 Sgr by Saturn: Saturn pole position and astrometry.

W. B. Hubbard, C. C. Porco, D. M. Hunten, G. H. Rieke, M. J. Rieke, D. W. McCarthy, V. Haemmerle, R. Clark, E. P. Turtle, J. Haller, B. McLeod, L. A. Lebofsky, R. Marcialis, J. B. Holberg, R. Landau, L. Carrasco, J. Elias, M. W. Buie, S. E. Persson, T. Boroson, S. West, and D. J. Mink. Icarus 103, 215-234 (1993) .


Saturn's ring plane-defined pole position is presently derived from the geometry of Saturn's July 3, 1989 occultation of 28 Sgr, as indicated by the timings of 12 circular edges in the Saturn C-ring as well as the edges of the Encke gap and the outer edge of the Keeler gap. The edge timings are used to solve for the position angle and opening angle of the apparent ring ellipses; the internal consistency of the data set and the redundancy of stations indicates an absolute error of the order of 5 km. The pole position thus obtained is consistent with the pole and ring radius scale derived from Voyager occultation observations.

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