Lighting Conditions for the Moon's Poles: Integrating Clementine, Kaguya, and Lunar Reconnaissance Orbiter Data Sets

Lunar poles experience extreme variations in illumination. Areas of permanent shadow and near-permanent illumination are located in close proximity and are attractive candidates for a sustained presence, exploration, and resource exploitation. Here we use Kaguya and Lunar Reconnaissance Orbiter (LRO) laser-altimeter (LALT and LOLA) digital topography models (DTMs) to simulate illumination conditions for both lunar poles using the software LunarShader. Previous comparisons between Clementine optical images and illumination maps derived from Kaguya LALT data suggest accurate and precise prediction of polar lighting conditions (Bussey et al. 2010). Here, maps predicting areas of illumination or shadow are generated at 12-hour intervals for the hypothetical year 2020. Average illumination maps computed from these data for time periods of one month to a year enable the identification and analysis of regions of both sustained illumination or permanent shadow and account for seasonal variations. Temporal illumination profiles are also generated for locations with more sustained illumination for more detailed analysis. Previous analyses focused on models derived from Kaguya DTM’s with high (64 pixels/degree) and low (128 pixels/degree) resolution data sets extending 5° and 10° from each pole (Bussey et al. 2010; Cahill et al. 2010). This work integrates LOLA data (~126 pixels/degree), which extends to 80° latitude. A comparison of average illumination for the three models prepared for the North pole predict similar durations of illumination during the year 2020. Kaguya low- and high-resolution models predict the region with the most sustained illumination will be lit 89% and 86% of the year, respectively. The illumination model computed from LRO’s LOLA data predicts this location will be lit 90% of year. At the South Pole, Kaguya high-resolution data simulations predict an illumination of 78%, 8-10% lower than the other data sets (86% for the Kaguya low-resolution and 90% for the LOLA). Although high-resolution Kaguya and LOLA data have similar spatial resolutions, noise in the Kaguya DTM require some smoothing to be performed as noted by Bussey et al. 2010. This smoothing, along with significant topographic relief changes at the South Pole, may be a contributing cause for the incongruous result from Kaguya high-res data product. Despite these discrepancies, all models suggest a similar set of locations with the highest sustained illuminations to previous studies (Bussey et al. 1999; Bussey et al. 2005). At the South Pole, these locations include four points (A, B, C, and D) on the rims of and near Shackleton and De Gerlache craters and a fifth location near summit of Malapert Mountain. For the North Pole, locations on the crater rims of Whipple and Aepinus have the most sustained illumination. These regions are studied in greater detail with LRO’s narrow-angle and wide-angle camera (NAC and WAC, respectively) images focusing on their geology and suitability for future exploration by robotic or manned missions.