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Lunar Brightness Variations with Phase at 4.3-MM Wave LengthThe lunar radio observations and interpretations of Piddington and Minnett (1949) and Gibson (1958) show that the lunar brightness variation with phase at millimeter wave lengths can be used to determine the physical properties of the lunar surface. They found that the millimeter-wave brightness lagged the optical phase, and their interpretation was that the millimeter radiation originates below a surface layer that is a very good thermal insulator. The thickness of this layer could not be determined from observations at one frequency. Observations at different frequencies give different results because of the wave-length dependence of the radio absorption by the surface material. The attenuation in the material increases with decreasing wave length, and therefore it is possible, in principle, to determine surface layer thickness from radio observations at several wave lengths. For this reason, observations of lunar radiation were started at the Naval Research Laboratory at a wave length of 4.3 mm. This is half the wave length used by Gibson (1958) in his earlier studies. The radio telescope used for these observations has been described in detail in a previous publication (Coates 1958). The antenna is a parabolic reflector 10 feet in diameter, and it has a beam width of 6.7 minutes of arc at the wave length of 4.3 mm. This is about one-fifth the diameter of the moon. The receiver was a Dicke-type radiometer.
Document ID
20150022974
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Coates, Robert J.
(NASA Headquarters Washington, DC United States)
Date Acquired
December 14, 2015
Publication Date
March 1, 1961
Publication Information
Publication: The Astrophysical Journal
Volume: 133
Issue: 2
Subject Category
Lunar And Planetary Science And Exploration
Distribution Limits
Public
Copyright
Other

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