This “illumination map” was constructed using over 1700 photographs of the same area of the moon’s south pole taken by the Lunar Reconnaissance Orbiter Camera (LROC) over a six month period.Because the moon’s rotational axis is tilted by only 1.54 degrees (compared to Earth’s 23.5 degrees), some areas near its poles are left in permanent shadow, while nearby regions remain sunlit for most of the year.
Each image taken by the LROC was projected onto a map of the area and converted to a binary image: if the ground was illuminated that pixel of the map was set to one, and if shadowed zero. Researchers then stacked all the binary images and calculated the percentage of the time each pixel was illuminated over the six month period.
The resulting “illumination map” is shown above. Areas that were never illuminated appear black, areas that were always illuminated are white, and areas that were sometimes illuminated and sometimes in shadow appear as varying shades of grey.
The Shackleton crater, 19 kilometres in diameter and 4 kilometres deep, can be seen at the centre of the image. The south pole is at approximately 9 o’clock on its rim.
The LROC is making daily (which is about 28 Earth days) and yearly illumination maps for both poles in preparation for future lunar missions.
source : http://www.newscientist.com/blogs/shortsharpscience/2010/12/iluminating-the-moons-south-po.html