Just before dawn Friday, a spacecraft is scheduled to punch a 13-foot-deep hole in a crater at the moon's south pole that hasn't seen sunlight in billions of years. The purpose: to find out whether ice is hidden there.
NASA's Lunar Crater Observation and Sensing Satellite, which set out for the moon in June, made a correction Tuesday to position itself to steer a rocket into the 2-mile-deep crater Cabeus at 6:30 a.m. CDT on Friday.
Four minutes later, if all goes well, the spacecraft will fly through the cloud of debris rising above the lunar surface and analyze it for evidence of water.
Back on Earth, amateur astronomers are expected to turn their telescopes to the show, which will last less than a minute. And scientists preparing for the collision are excited over what might turn up.
"The spacecraft is looking great. I don't think we could miss the moon now if we tried," said Steve Hixson, vice president of Advanced Concepts at Northrop Grumman Aerospace Systems in Redondo Beach, Calif., which built the craft.
"It's our job to confirm there is water there," said Dan Andrews, the project manager at Ames Research Center in Mountain View, Calif., which designed the spacecraft instruments. "But even if it's very dry, that's a good answer to have."
The LCROSS satellite was originally a $79 million add-on to the larger, $500 million Lunar Reconnaissance Orbiter, whose mission is to map the moon. But the theatrical nature of the Friday's impact has caught the public's attention. Events are scheduled at numerous sites across the nation, including Chicago's Adler Planetarium. However, the planetarium's Web site says the Friday morning show is sold out.
According to NASA, the rocket will create a dust cloud as high as six miles above the lunar surface, providing a show for amateur astronomers with telescopes 10 inches or larger.
For years after the Apollo flights of the 1960s and early '70s, scientists considered the moon a dry wasteland.
But in 1999, NASA's Lunar Prospector mission found evidence of hydrogen, a possible indicator of water, in permanently shadowed craters at both poles.
The crater-observing satellite launched June 18 attached to the Lunar Reconnaissance Orbiter. Shortly after launch, the two spacecraft separated. The orbiter began a year-long mission to map the moon. The sensing satellite went into a looping orbit around the Earth to line itself up for Friday's impact.