A Normalized View of Venus

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  • 1 Space Science and Engineering Center, University of Wisconsin, Madison 53705
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Abstract

It is now known that Venus has a fairly thick and massive atmosphere, the 10 mb level occurring at a height of about 80 km above the surface. Mariner 10 television observations agree with an isotropic scattering model with single scattering albedo of about 0.92 in the untralviolet region of the spectrum. Based on this knowledge, a few Mariner 10 images have been “normalized” to a standard scattering geometry using the exact solution by Chandrasekhar involving his H functions.

The most striking feature of the normalized images is the bright polar ring or cap beyond about 50° latitude circle and a narrower brightness frequency distribution. The brightness variation along a meridian shows substantial axial symmetry on a large scale, and small-scale brightness variations over the planet are no more than about 10%. Inferences regarding the polar cloud tops in light of available evidence are discussed.

The variation of mean brightness and of the ratio of mean square deviation of brightness to average brightness is comparable to the performance limits of the vidicon camera for the image sequence lasting about a day so that the variation in distribution of dark and bright features over the planet and the UV albedo of the planet over about a day is small.

Abstract

It is now known that Venus has a fairly thick and massive atmosphere, the 10 mb level occurring at a height of about 80 km above the surface. Mariner 10 television observations agree with an isotropic scattering model with single scattering albedo of about 0.92 in the untralviolet region of the spectrum. Based on this knowledge, a few Mariner 10 images have been “normalized” to a standard scattering geometry using the exact solution by Chandrasekhar involving his H functions.

The most striking feature of the normalized images is the bright polar ring or cap beyond about 50° latitude circle and a narrower brightness frequency distribution. The brightness variation along a meridian shows substantial axial symmetry on a large scale, and small-scale brightness variations over the planet are no more than about 10%. Inferences regarding the polar cloud tops in light of available evidence are discussed.

The variation of mean brightness and of the ratio of mean square deviation of brightness to average brightness is comparable to the performance limits of the vidicon camera for the image sequence lasting about a day so that the variation in distribution of dark and bright features over the planet and the UV albedo of the planet over about a day is small.

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