A lunar infrared spectrum from a balloon-borne system

Abstract

Infrared emission spectroscopy has been proposed by several workers as a remote sensing technique to determine the composition of the lunar surface layer. However, the amount of spectral information from a rock or mineral is reduced as its effective particle size is reduced, causing the feasibility of this technique to become problematic and dependent on the average particle size of the lunar surface material. Models, based on other optical evidence, indicate a layer of very fine material on the surface. This paper reports the first lunar infrared spectrum taken from above most of the Earth's atmosphere by means of a spectrometer aboard a 60-cm balloon-borne telescope. The spectrum does not exhibit spectral features which could be used for compositional identification of the lunar surface. In addition, the roles of residual atmospheric absorption, and thermal and compositional inhomogeneities in reducing the detectability of spectral features, as well as the thermal emissive behavior of possible lunar surface materials, are discussed.