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Science 2 February 1973:
Vol. 179. no. 4072, pp. 473 - 476
DOI: 10.1126/science.179.4072.473
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Articles

Venus: Radar Determination of Gravity Potential

Irwin I. Shapiro 1, Gordon H. Pettengill 1, Gary N. Sherman 1, Alan E. E. Rogers 2, and Richard P. Ingalls 2

1 Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge 02139
2 Haystack Observatory, Westford, Massachusetts 01886

We describe a method for the determination of the gravity potential of Venus from multiple-frequency radar measurements. The method is based on the strong frequency dependence of the absorption of radio waves in Venus' atmosphere. Comparison of the differing radar reflection intensities at several frequencies yields the height of the surface relative to a reference pressure contour; combination with measurements of round-trip echo delays allows the pressure, and hence the gravity potential contour, to be mapped relative to the mean planet radius. Since calibration data from other frequencies are unavailable, the absorption-sensitive Haystack Observatory data have been analyzed under the assumption of uniform surface reflectivity to yield a gravity equipotential contour for the equatorial region and a tentative upper bound of 6 x 10-4 on the fractional difference of Venus' principal equatorial moments of inertia. The minima in the equipotential contours appear to be associated with topographic minima.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Venus: Mass, Gravity Field, Atmosphere, and Ionosphere as Measured by the Mariner 10 Dual-Frequency Radio System.
H. T. Howard, H. T. Howard, G. L. Tyler, G. Fjeldbo, A. J. Kliore, G. S. Levy, D. L. Brunn, R. Dickinson, R. E. Edelson, W. L. Martin, et al. (1974)
Science 183, 1297-1301
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Science. ISSN 0036-8075 (print), 1095-9203 (online)