The cameras will also look for polar locations that enjoy near-constant sunlight - a boon to lunar bases hungry for solar electric power.
After a year of low-altitude study, LRO will shift to a higher, more stable orbit for several more years of lunar studies.
The second spacecraft, called Lunar CRater Observation and Sensing Satellite, will rocket off on a long, looping orbit around the Earth and moon. In October it will swing back for a violent encounter with the moon's south pole.
On its final approach, LCROSS will separate from its Centaur rocket booster. The booster, flying four minutes ahead of the satellite, will plunge to the lunar surface, sending up a plume of rock and dust on impact.
The satellite will then fly through the debris cloud, scan it for signs of water and other matter, and relay the data back to Earth. Then it, too, will crash and send up a second cloud of debris to be scanned by telescopes on Earth.
The impact target will be the floor of a polar crater that seldom if ever sees the sun. Previous missions have detected hydrogen in such frigid craters, and some scientists believe that's evidence of subsurface water ice - a potential source of drinking water, hydrogen and oxygen for lunar bases.
