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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.