**AAS 205th Meeting, 9-13 January 2005**

*Session 56 Planets and Solar System Objects*

Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall
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## [56.07] Nadir Emissivity Radiative Transfer Models For Planetary Regolith: Current State of the Art

*K. M. Pitman (Louisiana State University; Space Science Institute), M. J. Wolff (Space Science Institute), G. C. Clayton (Louisiana State University)*

A decade ago, a paradigm for theoretically calculating the
nadir emissivity values of planetary regolith laboratory
proxy samples was established in the literature: determining
single-scattering properties of the target light scattering
particles via Mie theory and incorporating
multiple-scattering via an analytical two-stream
approximation to the radiative transfer (RT) equation. While
a qualitative comparison between Mie/analytical RT hybrid
model and lab values performs reasonably, it is well known
that Mie theory is a gross simplification of scatterer
geometry; axially symmetric shapes used in interstellar dust
models may be substituted as an improvement. Astronomers,
accustomed to increasing the number of streams to 16 or
greater to accurately determine radiation field intensities
for diffuse media, generally seek out a 2-n stream
numerically exact RT solution, which may be inappropriate
for flux or mean intensity calculations. In this work, we
compare the performance of the most recent analytical
2-stream approximation method (Hapke 2002) and a popular
discrete ordinates numerically exact RT solution (Stamnes et
al. 1988) to determine strengths and weaknesses of each RT
solution method. We briefly discuss strategies to
incorporate better shape and particle packing assumptions
into planetary regolith emissivity models.

This work is supported through NASA MDAP (MJW, KMP).

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Bulletin of the American Astronomical Society, **36** 5

© 2004. The American Astronomical Society.