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Science 25 January 1980:
Vol. 207. no. 4429, pp. 449 - 453
DOI: 10.1126/science.207.4429.449
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Articles

Pioneer Saturn Celestial Mechanics Experiment

JOHN D. ANDERSON 1, GEORGE W. NULL 1, ELINOR D. BILLER 1, SUN KUEN WONG 1, WILLIAM B. HUBBARD 2, and JOSEPH J. MACFARLANE 2

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena 91103
2 Lunar and Planetary Laboratory, University of Arizona, Tucson 85721

During the Pioneer Saturn encounter, a continuous round-trip radio link at S band (sim 2.2 gigahertz) was maintained between stations of the Deep Space Network and the spacecraft. From an analysis of the Doppler shift in the radio carrier frequency, it was possible to determine a number of gravitational effects on the trajectory. Gravitational moments ( J2 and J4) for Saturn have been determined from preliminary analysis, and preliminary mass values have been determined for the Saturn satellites Rhea, Iapetus, and Titan. For all three satellites the densities are low, consistent with the compositions of ices. The rings have not been detected in the Doppler data, and hence the best preliminary estimate of their total mass is zero with a standard error of 3 x 10–6 Saturn mass. New theoretical calculations for the Saturn interior are described which use the latest observational data, including Pioneer Saturn, and state-of-the-art physics for the internal composition. Probably liquid H2O and possibly NH3 and CH4 are primarily confined in Saturn to the vicinity of a core of approximately 15 to 20 Earth masses. There is a slight indication that helium may likewise be fractionated to the central regions.

Submitted on December 3, 1979


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Radio Science Investigations of the Saturn System with Voyager 1: Preliminary Results.
G. L. TYLER, V. R. ESHLEMAN, J. D. ANDERSON, G. S. LEVY, G. F. LINDAL, G. E. WOOD, and T. A. CROFT (1981)
Science 212, 201-206
   Abstract »    PDF »
Saturnian Trapped Radiation and Its Absorption by Satellites and Rings: The First Results from Pioneer 11.
J. A. SIMPSON, T. S. BASTIAN, D. L. CHENETTE, G. A. LENTZ, R. B. MCKIBBEN, K. R. PYLE, and A. J. TUZZOLINO (1980)
Science 207, 411-415
   Abstract »    PDF »
Imaging Photopolarimeter on Pioneer Saturn.
T. GEHRELS, L. R. BAKER, E. BESHORE, C. BLENMAN, J. J. BURKE, N. D. CASTILLO, B. DACOSTA, J. DEGEWIJ, L. R. DOOSE, J. W. FOUNTAIN, et al. (1980)
Science 207, 434-439
   Abstract »    PDF »
Vertical Structure of the Ionosphere and Upper Neutral Atmosphere of Saturn from the Pioneer Radio Occultation.
A. J. KLIORE, G. F. LINDAL, I. R. PATEL, D. N. SWEETNAM, H. B. HOTZ, and T. R. MCDONOUGH (1980)
Science 207, 446-449
   Abstract »    PDF »


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