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arXiv 1208.4518astro-ph.EP
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受轨道观测约束的火星表面相函数

Mars surface phase function constrained by orbital observations

Mathieu Vincendon

摘要:

火星表面的光度特性描述了如何将表面反射率的远程测量与用于能量平衡计算的半球形反射率联系起来。一个简单的朗伯模型经常被假设为全球数据处理,即使通过一些本地的研究已经揭示了火星表面相函数的复杂性。在本文中,我们推导出一个平均的双向反射分布函数(BRDF)的火星平均超过公里大小的遥感器像素。欧米茄和CRISM数据用于提供全球范围内各种观测条件下太阳波长的观测约束。大气贡献的量化和删除使用辐射转移模型。一个共同的相位行为组成的一个5至10%的背散射峰与散射反射率随发射角的增加进行了观察。因此,地面反射率的最低点测量通常会低估半球反射率或反射率10%。我们提供了一个参数化的平均火星表面相函数的基础上Hapke形式主义(ω = 0.85,θ = 17,c = 0.6,b = 0.12,B0 = 1和h = 0.05),并量化的漫反射照明条件对火星的影响。我们的平均相函数可以用来作为一个改进相比,兰伯特模型在全球数据处理和气候建模。

英文摘要:

The photometric properties of the surface of Mars describe how remote measurements of surface reflectance can be linked to hemispherical albedo used for energy balance calculations. A simple Lambert model is frequently assumed for global data processing, even through several local studies have revealed the complexity of Mars surface phase functions. In this paper, we derive a mean Bidirectional Reflectance Distribution Function (BRDF) of Mars as averaged over km-sized remote sensor pixels. OMEGA and CRISM data are used to provide observational constraints at solar wavelengths over a wide range of viewing conditions all over the planet. Atmospheric contribution is quantified and removed using a radiative transfer model. A common phase behavior composed of a 5 to 10% backscattering peak associated with an increase of scattered reflectance with emission angle is observed. Consequently, nadir measurements of surface reflectance typically underestimate hemispherical reflectance, or albedo, by 10%. We provide a parameterization of the mean Mars surface phase function based on Hapke formalism (ω = 0.85, θ = 17, c = 0.6, b = 0.12, B0 = 1 and h = 0.05), and quantify the impact of the diffuse illumination conditions reigning on Mars. Our average phase function can be used as a refinement compared to the Lambert model in global data processing and climate modeling.

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