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[15.26] Using Directional Emissivity as a Probe of Particle Microphysical Properties

K. M. Pitman (Louisiana State University), M. J. Wolff (Space Science Institute), J. L. Bandfield (NASA/GSFC), G. C. Clayton (LSU)

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values are a function of viewing geometry. This fact has strong implications for analyses of the MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset. As reviewed previously [1], in the absence of strong thermal gradients, directional emissivity may be obtained via a combination of reciprocity and Kirchhoff's Law.

Here we focus on the potential utility of directional emissivity as a direct probe of surface particle microphysical properties. We explore the effects of particle size and composition on observed radiances in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to TES EPF observations of typical surface units (e.g., high and low albedo regions) will also be made.

This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP).

[1] Pitman, K.M., et al. (2001), AAS-DPS meeting # 33, # 36.01.

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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.