Albedo and photometry of surveyor footprints |
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| Authors: | J D Halajian |
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| Institution: | Grumman Aircraft Engineering Corporation, Bethpage, New York, USA |
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| Abstract: | This article deals with the gray tone differences between the undisturbed lunar surface and the darker ejecta observed around Surveyor 1 footpads. Albedo (i.e. compositional) differences between the surface and subsurface layers or a mere difference of porosity between the undisturbed and disturbed materials are two reasonable hypotheses that nave been suggested to account for the observations. These hypotheses are examined in the light of Surveyors 3, 5 and 6 data and photometric and photographic studies of footprints in simulated lunar soils. While evidence favors the latter hypothesis, it is not conclusive. The author suggests that detailed data on the directional albedo (at or near ‘opposition’) of the Surveyor footprints could, in most cases, help discriminate between compositional and shadowing effects on the gray tones observed at large phase angles; also the area under the normalized photometric curve can be used as a convenient index of surface porosity and, by inference, of packing density. |
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