Illumination Conditions in the Lunar Polar regions from Lunar Orbiter Laser Altimeter (LOLA) Data

We investigate the illumination conditions in the polar regions of the Moon using topographic data from the Lunar Orbiter Laser Altimeter (LOLA). From end of June to mid-September 2009, the Lunar Reconnaissance Orbiter (LRO) was in commissioning phase, in an elliptical (~30x200km) polar orbit, with its periapsis near the south pole. As a result, initial data collection and analysis has emphasized the southern hemisphere, particularly the south polar region. We construct Digital Elevation Models (DEMs) of various resolutions to survey areas with extreme lighting conditions: permanently shadowed regions (PSRs) and potential peaks of eternal light (PELs). We use the horizon shadow method (e.g., Dozier et al., 1981) over the ray-tracing approach, as it enables fast computations once the initial expensive computations are done. This allows us to explore the full range of possible Sun positions. After performing the calculations on relatively-coarse DEMs, higher-resolution models are used around specific areas of interest, in particular the LCROSS impact site. In addition to direct insolation, we assess, in a simplified way, the extent to which PSRs can be affected by scattered light. We compare our results to previous work performed with Kaguya LALT data (e.g., Noda et al., 2008). References: Dozier, J., J. Bruno, P. Downey (1981), "A Faster Solution to the Horizon Problem", Computers and Geosciences, vol.7, pp. 145-151. Noda, H., H. Araki, S. Goossens, Y. Ishihara, K. Matsumoto, S. Tazawa, N. Kawano, S. Sasaki (2008), Illumination conditions at the lunar polar regions by KAGUYA(SELENE) laser altimeter, Geophys. Res. Lett., 35, L24203, doi:10.1029/2008GL035692.