Refraction and multiple scattering of solar radiation in a planetary atmosphere cause the propagation of appreciable amounts of radiative energy into the planet's geometric shadow cone. The implications of this atmospheric phenomenon for research in various fields are discussed. Examples are studies of lunar eclipses, the presence of the Venus ring near inferior conjunction, the astronomical problem of the appearance of the earth as a planet, and the flights of spacecraft in earth orbit and in cislunar space. The results of such studies provide data in disciplines involving geophysics, planetary atmospheres, solar physics, astronomy, and astronautics. Rigorous solutions of radiative transfer problems in a real atmosphere, however, still are beyond the capabilities of present theory. Some preliminary quantitative results in the visible range of the electromagnetic spectrum have been obtained through the use of a semiempirical method. This technique promises to become a useful tool in the fields of study discussed. 26 pp. Bibliog.
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