NASA's mission: Can we live on the moon?

Nearly four decades after astronaut Neil Armstrong planted his boot on the surface of the moon, the U.S. is about to take the first small step toward colonizing Earth's tag-along satellite.

On Wednesday, NASA is scheduled to launch a robotic mission aimed at finding the best site for Earth's first off-world colony, the centuries-old dream of science fiction writers and utopians.

This time, we're not just going for a walkabout or to hit golf balls and cruise around in a $10-million moon-buggy, as the Apollo astronauts did. Ultimately, we hope to pack up the kids and the dog and move in.

"We're going to provide NASA with what is needed to get human beings back to the moon and to stay there for an extended duration," said Craig Tooley, project manager for the Lunar Reconnaissance Orbiter, one part of the two-pronged mission.

The orbiter itself is expected to produce the most detailed topographic maps of the moon ever made, as well as first-ever glimpses inside perpetually shadowed craters at the north and south poles. Inside those craters, scientists hope to find caches of frozen water that have been hidden away for billions of years.

The mission won't stop there. Using a second spacecraft -- the Lunar Crater Observation and Sensing Satellite -- NASA is planning to punch a hole in one to see what comes out.

Both of the spacecraft will be launched together with a two-stage rocket, and nearly four months from now, the agency will use the spent second stage of the rocket as a battering ram to create a crater 66 feet wide by 13 feet deep and send a 6-mile-high plume wafting into space that should provide a show for hobbyists on Earth with decent-sized telescopes.

"This should be spectacular," said Tony Colaprete, the satellite's project scientist. "It should be a very visible impact from Earth."

The biggest uncertainty hanging over the $579-million mission as it prepares for launch at Cape Canaveral in Florida is the question of whether the lunar outpost will ever be built.

The plan for a lunar colony was developed as a consequence of President George W. Bush’s 2004 Vision for Space Exploration, which proposed putting human beings back on the moon by 2020. That plan also called for using the moon as a jumping-off point for a still more ambitious plan to put astronauts on Mars.

But President Obama has not endorsed the Bush vision.

The administration's recent decision ordering a review of the future of human spaceflight stirred anxieties in the passionate space community. Some observers wonder whether Obama is setting the stage for a pullback from Bush's grand vision to a much more limited one -- similar to the one that led NASA to abandon the moon in the '70s in favor of the much-derided space shuttle program.

In his May 19 testimony to a Senate science subcommittee, Christopher Scolese, acting NASA administrator, indicated that he was well aware the long-term plan for humans to colonize other worlds could be in danger. He took note of the fact that "the administration will provide an updated request for exploration activities, as necessary."

"In the meantime," he said, "NASA is proceeding as planned with current exploration activities, including . . . lunar systems."

An hour after launch on Wednesday, the 4,000-pound reconnaissance orbiter will separate from the crater-sensing satellite and rocket portions of the spacecraft. After a nearly five-day cruise, it will use a dozen guidance thrusters to settle into orbit about 30 miles above the lunar surface, which is much more a mystery than many might think.

Other than the equatorial area explored by the Apollo missions, "images of the rest of the moon are pretty poor," Tooley said. "We have much better images of Mars than the moon."

The problem is particularly acute at the poles, where the current maps can be off as much as 10 miles, even though the current NASA plan calls for establishing the outpost at one of the poles.

Both poles have areas with both perpetual sunlight and perpetual shade. The sunlight would be useful as a source of solar power for colonists. The shaded areas may feature deposits of ice that have been locked up for billions of years.

Such ice could be used not just as a source of water. Through electrolysis, it could be broken down into hydrogen and oxygen. The oxygen could be used both for respiration and to make rocket fuel for trips back and forth to Earth. But there's no definitive proof ice is there. The possible presence of water on the moon "is a hotly and passionately debated topic," Tooley said.

Tantalizing clues point in both directions. One of the most persuasive came from the 1998 Lunar Prospector mission, which detected large stores of hydrogen in sunken craters, where the temperature never rises above minus 270 degrees. Yet, recent efforts to find water with other international satellites orbiting the moon have failed.

The current mission aims to answer that question and strip away the last shrouds of mystery from the moon.

The lunar orbiter carries seven instruments, among them a set of cameras that can resolve features as small as 18 inches across, the size of a small boulder.

A laser altimeter will bounce beams off the surface to create a detailed view of the landscape -- mountains, ridges and valleys. An instrument dubbed CRaTER will measure the radiation environment. NASA has long known that exposure to cosmic and solar radiation is a health hazard for anyone living on the lunar surface.

"If we're going to stay on the moon a long time, we're going to have to figure out how to protect ourselves," Tooley said.

The Lunar Reconnaissance Orbiter will have a good chance of finding water, if it's there. But sometimes, nothing beats getting your hands dirty, and that's where the Lunar Crater Observation and Sensing Satellite comes in.

After the orbiter parts company with the satellite and rocket shortly after launch, the crater-busting combo will go into a looping Earth orbit to line up a space-based knockout blow on the moon. The punch will be delivered by the second-stage of the Atlas V rocket (now devoid of fuel), called a Centaur. After sling-shotting around the Earth to gain momentum and achieve the highest possible angle for its plunge into the moon, the SUV-sized Centaur will barrel into the targeted crater on the morning of Oct. 8 at about 5,600 mph. It will shatter any surface ice and send up a huge plume of dust.

Four minutes after the collision, the accompanying satellite will fly through the debris to take measurements of the chemical composition. Any water blasted out of the crater will quickly decompose. But the satellite carries among its nine instruments a set of visible light and infrared cameras, as well as spectrometers, specifically designed to spot the decomposing chemicals.

After flying through the vapor cloud, the satellite will crash into the lunar surface some distance away. Miles above, watching the drama unfold, will be the reconnaissance orbiter. And a bit farther away, down on terra firma, hobbyists by the thousands will be training their telescopes on the moon's underbelly.

NASA still hasn't decided which crater to pummel. It must be shallow enough that the material blasted out can rise above the rim so the spacecraft can fly through it to take measurements, Colaprete said.

NASA won't settle on a target until 30 days before impact, when it will have the orbiter's measurements to help guide the choice.

It could take months to unravel what the spacecraft find. But if they turn up unequivocal proof of water on a purportedly dead world, no one is going to sit on that bombshell.

"If we hit a high concentration of water, we will report that as soon as we can," Colaprete said.