The spin axis of the Moon is tilted by only 1.5° (compared with the Earth's 23.5°), leaving some areas near the poles in permanent shadow, while other nearby regions remain sunlit for the majority of the year. Theory, radar data, neutron measurements, and Lunar CRater Observation and Sensing Satellite (LCROSS) observations suggest that volatiles may be present in cold traps in permanently shadowed regions. Thus, areas of near permanent illumination are prime locations for future lunar outposts due to their benign thermal conditions and near constant accessibility to solar power.
One of the primary scientific objectives of the Lunar Reconnaissance Orbiter Camera (LROC) is to unambiguously identify regions of permanent shadow and near permanent illumination using its two imaging systems that provide medium and high-resolution views of the poles. While in a 50-km polar orbit (September 2009 to December 2011), LRO acquired thousands of Wide Angle Camera (WAC) images of each pole every ~2 hours. Occasional spacecraft and instrument disturbances caused some imaging opportunities to be missed, however the average time between WAC observations remained at 2.3 hours.
When LRO passes over each pole, the WAC images from 80° to 90° on the dayside and back to 80° on the night side. The WAC 90° field of view (monochrome mode) allows for a 104-km region within 2° degrees of the pole to be acquired at a resolution of 100 m/pixel. Speyerer and Robinson (2013) compiled these images into a year-long illumination movie in order to identify regions near each pole that remained illuminated for a majority of the year.
As part of this Reduced Data Record (RDR) product, we have included 8170 WAC images of the south pole acquired between 2009-09-20 and 2011-12-11. In addition, we have compiled a Quicktime (.mov) movie file using 4668 WAC images acquired between 2010-04-02 and 2011-06-13. This time period is ideal, since there are not many long temporal gaps between WAC observations. The movie files are available in two sizes: cropped and reduced. The cropped version is sampled at 100 m/pixel and is centered at the south pole. The reduced resolution version is sampled at ~560 m/pixel to enable the entire WAC image out to 80°s to be displayed within a 1080x1080 pixel area.
Each WAC image was processed using the latest camera model available (Speyerer et al., 2014) with improved spacecraft ephemeris provided by the LOLA/GRAIL team (Mazarico et al., 2013). A partial lunar eclipse is visible on 2010-06-26 at 12:30:21 UTC.
The 8190 WAC polar movie frames are archived here.
|Product||File Size||Date Range||Number of WAC Images|
|Cropped version (Quicktime)||2.29 GB||2010-04-02 to 2011-06-13||4668|
|Reduced version (Quicktime)||459 MB||2010-04-02 to 2011-06-13||4668|
References:E. Mazarico et al. (2013) Improved Orbit Determination of Lunar Orbiters with Lunar Gravity Fields Obtained by the GRAIL Mission, 44th Lunar and Planetary Science Conference, Abstract #2414.
E.J. Speyerer and M.S. Robinson (2013) Persistently illuminated regions at the lunar poles: Ideal sites for future exploration, Icarus 222, pp. 122-136. doi:10.1016/j.icarus.2012.10.010
E.J. Speyerer et al. (2014) Pre-flight and On-orbit Geometric Calibration of the Lunar Reconnaissance Orbiter Camera, Space Science Reviews. doi:10.1007/s11214-014-0073-3