Letter | Published:

Photometric confirmation of the Encke division in Saturn's ring A

Naturevolume 272pages601602 (1978) | Download Citation



APPROXIMATELY once every 15 yr, it is possible to observe Saturn's satellite lapetus passing through the shadow of the rings. Observations of such events are of great value to studies of the optical properties of the rings, as ground-based observations of reflected light are limited to a small range of phase angles near zero ( |ϕ|< 6°), and eclipses give transmission data at ϕ = 180°. During the current apparition, lapetus experiences two eclipses, the first having occurred on 19–20 October 1977, and the second 7–8 January 1978. The observed brightness of Tapetus during eclipse represents a spatial convolution of light from the limb-darkened disk of the Sun with the transmission of the rings and the non-uniform reflectivity over the disk of lapetus. We have examined this physical model through a computer simulation of the eclipse and use this to give here photometric confirmation of the Encke division in ring A.

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  1. Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, 85721

    • H. J. REITSEMA


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