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° 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. Each file is named with the following pattern:
WAC_MOVIE_[N|S]YYYYMMDDThhmm
where:
- [N|S] indicates the map pole (N=North or S=South)
- YYYY indicates the year of the observation
- MM indicates the month of the observation
- DD indicates the day of the observation
- T is a date and time separator
- hh indicates the hour of the observation (24-hour format)
- mm indicates the minute of the observation
The times used in the naming scheme are the start times of the WAC observations in UTC. All
south pole products are map projected in polar stereographic with the center latitude of -90°
and center longitude of 0° sampled at 100 m/pixel covering -80° to -90°. A LOLA shape
model (Smith et al. 2010) was used to remove mapping distortions due to topography. 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). The
image header includes the mapping information, start and stop times, along with the WAC image
name used to make the individual product.
In addition, we have compiled QuickTime (.mov) and MPEG-4 (.mp4) movie files 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.
Low-resolution 8-bit browse products in PNG format for this product, along with full-resolution
8-bit GeoTIFFs, are availablãe at the following location, with names matching those of the full-resolution IMG files:
http://lroc.sese.asu.edu/data/LRO-L-LROC-5-RDR-V1.0/LROLRC_2001/EXTRAS/BROWSE/WAC_POLE/WAC_POLE_MOVIE_SOUTH/
A partial lunar eclipse is visible on 2010-06-26 at 12:30:21 UTC.
When citing this product, use the following reference: Speyerer, E. J., & Robinson, M. S. (2013). Persistently
illuminated regions at the lunar poles: Ideal sites for future exploration. Icarus, 222(1), 122-136.
doi:10.1016/j.icarus.2012.10.010
The 8170 WAC polar movie frames are archived
here.
References:
D. E. Smith et al. (2010). Initial observations from the lunar orbiter laser altimeter (LOLA).
Geophysical Research Letters, 37(18). doi:10.1029/2010GL043751
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
For more information on LROC Reduced Data Records (RDRs), please refer to the
LROC RDR Software Interface Specification (SIS).