CAPE CANAVERAL, Fla. (AP) _ For the second night in a row, NASA aimed for the moon Tuesday, hoping to launch an orbiting spacecraft to look for water that could one day be used by human settlers.

It's NASA's first moon mission in 25 years.

Tuesday night was the space agency's last chance this month to launch the unmanned Athena rocket carrying the Lunar Prospector. The next opportunity for the most fuel-efficient route to the moon is Feb. 3.

Monday's launch attempt was foiled by the failure of Air Force radar needed to track the rocket for safety reasons. The system was fixed Tuesday.

After a 4 1/2-day trip to the moon, Prospector will slip into a 60-mile-high orbit and search for evidence of frozen water as well as minerals and gases. The spacecraft has five science instruments, including a neutron spectrometer that will look for excess hydrogen, an indication of water.

Some scientists believe the moon's shadowy poles hold as much as 1 billion tons of water ice, a theory bolstered by the military's Clementine spacecraft, launched to the moon in 1994.

If that's so, astronauts living on lunar bases could mine the water and separate it into hydrogen and oxygen for rocket fuel.

The 4-foot, 650-pound Prospector will survey the entire moon, orbiting from pole to pole. The $63 million mission is expected to last at least a year.

The spacecraft eventually will crash-land on the lunar surface, joining the trash and equipment left behind by the 12 astronauts who walked on the moon.

NASA last explored the moon in December 1972 with Apollo 17.