Abstract Permanently shadowed regions (PSRs) at the lunar poles are of unique interest for science and exploration due to their low surface temperatures and potential for volatile sequestration. While not directly illuminated by the Sun, PSRs are exposed to faint sources of radiation such as starlight, Lyman alpha photons from the interplanetary medium, and sunlight scattered from the surrounding topography. These illumination sources are significant as they contribute to the thermal energy budget of PSRs, and also provide a photon source with which to observe areas otherwise obscured by shadow. In this work, we survey the illumination conditions from the aforementioned sources within northern and southern hemisphere PSRs at far ultraviolet (FUV), visible (vis) and infrared (IR) wavelengths. With respect to magnitude, it is shown that scattered sunlight is the brightest radiation source to reach the PSRs in the visible and IR spectral regimes. As well, we show that scattered sunlight contributes a considerable supply of FUV photons, and may exceed the interplanetary medium/starlight brightness in many PSR craters due to the temporal and spatial variance of scattered sunlight. This finding suggests a higher rate of photodesorption and lower adsorption residence times for water molecules than previously suggested, and, furthermore, indicates that this rate fluctuates diurnally, seasonally and geographically owing to the variability of the incoming solar flux. Large differences in the received solar energy are found between craters, with crater latitude and size being among the modulating influences. Within individual craters, strong spatial heterogeneities in scattered solar flux are found, with equator-facing PSR slopes receiving 40%–60% of the total energy of slopes oriented toward the pole. Finally, we show that the radiation available is sufficient to detect water ice using vis/FUV or vis/IR filter pairings, and such observations can be made with signal to noise > 10 with an FUV-sensitive camera; however, with more scattered solar photons available for IR imaging, higher signal to noise ratios can be attained with a vis/IR filter pairing.

中文翻译：

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月球两极永久阴影区域内的照明条件：对原位被动遥感的影响

摘要 月球极地的永久阴影区 (PSR) 因其表面温度低和潜在的挥发性封存而对科学和探索具有独特的兴趣。虽然没有被太阳直接照射，但 PSR 会暴露于微弱的辐射源，例如星光、来自行星际介质的莱曼阿尔法光子以及从周围地形散射的阳光。这些照明源非常重要，因为它们有助于 PSR 的热能预算，并且还提供了一个光子源，用于观察否则会被阴影遮挡的区域。在这项工作中，我们在远紫外 (FUV)、可见光 (vis) 和红外 (IR) 波长下调查了北半球和南半球 PSR 内上述光源的照明条件。就量级而言，结果表明，在可见光和红外光谱范围内，散射的阳光是到达 PSR 的最亮的辐射源。同样，我们表明散射的阳光贡献了大量的 FUV 光子，并且由于散射阳光的时间和空间变化，可能会超过许多 PSR 陨石坑中的行星际介质/星光亮度。这一发现表明，水分子的光解吸速率比先前建议的更高，吸附停留时间更短，此外，还表明由于入射太阳通量的变化，该速率在昼夜、季节性和地理上波动。在陨石坑之间发现了接收到的太阳能的巨大差异，其中陨石坑的纬度和大小是调制影响之一。在个别陨石坑内，发现散射太阳通量存在强烈的空间异质性，面向赤道的 PSR 斜坡接收了 40%–60% 的斜坡总能量，朝向极点。最后，我们表明可用的辐射足以使用可见光/FUV 或可见光/红外滤光片配对检测水冰，并且可以使用 FUV 敏感相机在信噪比 > 10 的情况下进行此类观察；然而，随着更多散射的太阳光子可用于红外成像，使用可见光/红外滤光片配对可以获得更高的信噪比。10 配备 FUV 敏感相机；然而，随着更多散射的太阳光子可用于红外成像，使用可见光/红外滤光片配对可以获得更高的信噪比。10 配备 FUV 敏感相机；然而，随着更多散射的太阳光子可用于红外成像，使用可见光/红外滤光片配对可以获得更高的信噪比。