The moon will drift into NASA's cross hairs again Wednesday as the space agency prepares to launch two new spacecraft to search for the best places for humans to land when they return as early as 2020.
One of the two will crash its rocket booster into a polar crater, then fly through the debris plume to scan for water ice. The second, conceived and built in Maryland, will orbit the moon for at least a year. Its goal is to find safe landing sites with the water and sunshine needed to help sustain a permanent manned base.
The missions are NASA's first to orbit the moon since Lunar Prospector in 1999, and the first to reach the surface since the final Apollo landing in 1972. Two foreign satellites - one Chinese and one Indian - are currently orbiting the moon. A Japanese probe crash-landed on June 10.
"We're really ready and eager to go. ... We don't expect to have any problems," said Richard R. Vondrak, project scientist for the Lunar Reconnaissance Orbiter, which was built at the NASA Goddard Space Flight Center in Greenbelt.
"NASA hopes that, from the LRO and the other missions ... that we will have enough information to design the systems to return to the moon and pick the best places" to land, Vondrak said.
Both spacecraft are poised at the Cape Canaveral Air Force Station for a 3:51 p.m. launch on Wednesday atop an Atlas V rocket.
Five years in development, the two missions will cost a total of $580 million.
The launches could be delayed if NASA officials decide to instead launch the Endeavour space shuttle, which is being repaired after a leak scuttled its launch Saturday.
Once in space, the satellites will separate and take very different paths. The Lunar Reconnaissance Orbiter will make the four-day crossing to the moon, settle into a circular orbit and begin a long period of study with six onboard instruments.
LRO will measure the solar and cosmic radiation that long-term lunar explorers will encounter on the surface, and test its potential impact on human health.
Apollo astronauts spent only a few days on the lunar surface, Vondrak said. The next explorers will want to learn to live and work there for longer periods.
"In Apollo, we were willing to accept more risk than we are today. There's not the same sense of national emergency," he said. "We want to do it in a better way."
Other LRO instruments will measure changes in surface and subsurface temperatures and search for evidence of water ice and frost.
