The lunar opposition effect is the increase of brightness on the lunar surface when the phase angle approaches 0°, which is caused mainly by shadow‐hiding and coherent backscattering. However, the contribution of coherent backscattering is not yet well established. This study analyzes the contribution of coherent backscattering to the opposition effect using the correlation between the contribution of increased brightness of the theoretical coherent backscattering and the grain size of the reflecting surface. We analyze the correlation between the two using data from the Lunar Reconnaissance Orbiter Wide Angle Camera and median grain size d calculated by linear polarization observations. The size of effective scatterers of coherent backscattering is similar to the observation wavelength. In this case, the effective scatterer size for coherent backscattering is 0.6 μm. The results of our analyses show that there is no correlation between d and reflectance phase curve in the phase angle range from 0° to 6°. In addition, we analyze the distribution of grain size of lunar samples collected during the Apollo and Luna missions. We find an inversely proportional correlation between mean grain sizes and submicron grain content in the lunar samples. Therefore, d seems to indicate the content of effective scatterer. The strength of the coherent backscattering opposition effect seems to be affected by the content of the submicron grains. Thus, the lack of correlation between d and the opposition effect seems to imply minimal contribution of coherent backscattering to the lunar opposition effect.

中文翻译：

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月球表面亮度相曲线的粒度依赖性

月球对立效应是相角接近0°时月球表面亮度的增加，这主要是由于阴影隐藏和相干的反向散射引起的。但是，相干后向散射的作用尚未很好地确定。这项研究使用理论上相干背向散射的增加亮度的贡献与反射面的晶粒尺寸之间的相关性，分析了相干背向散射对相对效应的贡献。我们使用月球侦察轨道飞行器广角相机的数据和中值晶粒尺寸d分析了两者之间的相关性通过线性极化观测计算。相干反向散射的有效散射体的大小类似于观察波长。在这种情况下，用于相干反向散射的有效散射体尺寸为0.6μm。我们的分析结果表明，在0°至6°的相位角范围内，d与反射率相位曲线之间没有相关性。此外，我们分析了在阿波罗和月神任务期间收集的月球样品的晶粒尺寸分布。我们在月球样品中发现平均晶粒尺寸与亚微米晶粒含量之间成反比关系。因此，d似乎表明了有效散射体的含量。相干反向散射相反效应的​​强度似乎受亚微米晶粒含量的影响。因此，d与对立效应之间缺乏相关性似乎暗示着相干反向散射对月球对立效应的贡献最小。