The Occultation of 28 Sgr by Saturn: Saturn Pole Position and Astrometry

William B. Hubbard, C. C. Porco, D. M. Hunten, George H. Rieke, Donald W Mccarthy, 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. BorosonS. West, D. J. Mink

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Abstract

We determine the geometry of the 3 July 1989 occultation of 28 Sgr by Saturn and use the results to derive Saturn's pole as defined by the ring plane. The analysis makes use of high-precision timings of 12 circular edges in the C-ring (radii = 84750 to 90615 km), three features in the Cassini division, the edges of the Encke gap, and the outer edge of the Keeler gap. Our group of observing sites includes one southern hemisphere station (CTIO) and five northern hemisphere stations (three Tucson-area stations, the UK Infrared Telescope in Hawaii, and San Pedro Mártir in Baja California), which provides a terrestrial chord separation ∼10,000 km. Assuming ring radii obtained from an analysis of Voyager radio- and stellar-occultation data (P. D. Nicholson, M. L. Cooke, and E. Pellon, 1990, Astron. J.100, 1339-1362), we use edge timings to solve for the position angle and opening angle of the apparent ring ellipses. The star 28 Sgr appears to be well represented as a uniformly illuminated disk with an apparent radius of 9.0 ± 0.3 km projected at Saturn at the wavelengths of observation (λ ∼ 3 μm). The internal consistency of the data set and redundancy of stations indicates that the relative positional error of a given sharp ring edge timing is at the level of 2 km or smaller; the absolute error is roughly 5 km. Our derived pole position, αP = 40.599° ± 0.020°, δP = 83.536° ± 0.005°, is consistent with the pole and ring radius scale deduced from Voyager stellar and radio occultation observations (P. D. Nicholson, M. L. Cooke, and E. Pelton, 1990, Astron. J.100, 1339-1362) and the solution found in the accompanying paper (French et al., 1993, this issue).

Original languageEnglish (US)
Pages (from-to)215-234
Number of pages20
JournalIcarus
Volume103
Issue number2
DOIs
StatePublished - Jun 1993

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astrometry
occultation
Saturn
poles
rings
stations
stellar occultation
radio occultation
radii
time measurement
radio
ellipse
Lower California (Mexico)
Southern Hemisphere
infrared telescopes
Northern Hemisphere
ellipses
redundancy
wavelength
geometry

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

The Occultation of 28 Sgr by Saturn : Saturn Pole Position and Astrometry. / Hubbard, William B.; Porco, C. C.; Hunten, D. M.; Rieke, George H.; Mccarthy, Donald W; McCarthy, D. W.; Haemmerle, V.; Clark, R.; Turtle, E. P.; Haller, J.; McLeod, B.; Lebofsky, L. A.; Marcialis, R.; Holberg, J. B.; Landau, R.; Carrasco, L.; Elias, J.; Buie, M. W.; Persson, S. E.; Boroson, T.; West, S.; Mink, D. J.

In: Icarus, Vol. 103, No. 2, 06.1993, p. 215-234.

Research output: Contribution to journalArticle

Hubbard, WB, Porco, CC, Hunten, DM, Rieke, GH, Mccarthy, DW, McCarthy, DW, Haemmerle, V, Clark, R, Turtle, EP, Haller, J, McLeod, B, Lebofsky, LA, Marcialis, R, Holberg, JB, Landau, R, Carrasco, L, Elias, J, Buie, MW, Persson, SE, Boroson, T, West, S & Mink, DJ 1993, 'The Occultation of 28 Sgr by Saturn: Saturn Pole Position and Astrometry', Icarus, vol. 103, no. 2, pp. 215-234. https://doi.org/10.1006/icar.1993.1067
Hubbard, William B. ; Porco, C. C. ; Hunten, D. M. ; Rieke, George H. ; Mccarthy, Donald W ; McCarthy, D. W. ; Haemmerle, V. ; Clark, R. ; Turtle, E. P. ; Haller, J. ; McLeod, B. ; Lebofsky, L. A. ; Marcialis, R. ; Holberg, J. B. ; Landau, R. ; Carrasco, L. ; Elias, J. ; Buie, M. W. ; Persson, S. E. ; Boroson, T. ; West, S. ; Mink, D. J. / The Occultation of 28 Sgr by Saturn : Saturn Pole Position and Astrometry. In: Icarus. 1993 ; Vol. 103, No. 2. pp. 215-234.
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AU - Porco, C. C.

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AU - Rieke, George H.

AU - Mccarthy, Donald W

AU - McCarthy, D. W.

AU - Haemmerle, V.

AU - Clark, R.

AU - Turtle, E. P.

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AU - McLeod, B.

AU - Lebofsky, L. A.

AU - Marcialis, R.

AU - Holberg, J. B.

AU - Landau, R.

AU - Carrasco, L.

AU - Elias, J.

AU - Buie, M. W.

AU - Persson, S. E.

AU - Boroson, T.

AU - West, S.

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