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K. M. Pitman (Louisiana State University; Space Science Institute), M. J. Wolff (SSI), G. C. Clayton (LSU)
When particles are in near or close contact, they no longer scatter light like single particles. This is problematic for radiative transfer analyses of the photometric properties of surfaces such as the Martian regolith. Despite the community's best efforts, radiative transfer (RT) models are still inadequately predicting laboratory emissivity measurements at nadir, calling even the most fundamental of model assumptions into question [1]. To address these concerns from an empirical standpoint, we present a series of sensitivity studies performed to quantify the effects of single scattering albedo and asymmetry parameter (packed, unpacked cases) on emissivity in the thermal IR (TES, THEMIS, and mini-TES instrument wavenumber ranges) for micron-sized alpha quartz dust grains. By upgrading numerical algorithms from previous works [2, 3], we utilize hybrid solutions (Mie theory + discrete ordinates RT algorithm [4]) to calculate theoretical nadir emissivity values. We demonstrate that assumptions about the scatterer itself, rather than the machinery of the RT method used, constitute the most crucial aspect of modeling nadir emissivity values.
This work is supported through NASA MDAP (MJW, KMP).
[1] Piatek, J. L., et al. (2003) AAS-DPS #35, #05.04. [2] Moersch, J. E., & Christensen, P. R. (1995) JGR, 100, E4, 7465-7477. [3] Wald, A. E., & Salisbury, J. W. (1995) JGR, 100, B12, 24665-24675. [4] Stamnes, K., et al. (1988) Appl. Opt., 27, 2502-2509.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.