Washington - NASA was in the final countdown Thursday before launching a dual moon mission intended to pave the way for humans to return to the moon.

Launch was set for 2112 from Florida's Cape Canaveral, where the Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS) are to blast off aboard a single rocket.

The launch is the first step to implementing NASA's new space drive back to the moon. Next year, NASA will retire the ageing, 27- year-old shuttle programme that has built the space station and maintained the orbiting deep space telescope, the Hubble.

The moon, untouched since the manned landings of the late '60s and early '70s, would eventually serve as a jumping-off platform for exploring Mars, according to NASA's long-term objectives as set by former president George W Bush.

Thursday's two moon-bound craft are to send data back to NASA to help scientists find the best location for a manned spacecraft landing. The question of whether there is water on the moon, in the form of ice deep inside its craters, is key to the mission.

The LRO will immediately start orbiting the moon for about a year, taking the most detailed images yet of the lunar surface, creating three-dimensional maps that are accurate to within one metre, showing details as small as boulder. It will measure radiation on the surface to scout for possible dangers to astronauts.

The LCROSS will focus on determining whether water could be hidden in the shadowy craters of the moon near its poles. An earlier lunar satellite found high levels of hydrogen in the atmosphere near the poles, a hint that water could be present.

LCROSS's mission is to loop back around Earth and position itself around the moon so it can crash into a deep moon crater in about 110 days. The cloud of dust will be measured by a second, trailing device that will transmit its information to Earth and also crash into the moon.

The total event will last just 120 seconds, but scientists say the impact will provide valuable information to be collected on nine instruments, including five cameras that capture images in colour, thermal and near infrared images.

Images of the impact will also be captured by the orbiting LRO, as well as the Hubble Space Telescope and other telescopes on Earth. The composition of the material kicked up by the impact will help scientists deduce whether water is present.

But more low-tech instruments will also be able to see the impact, which should be visible to amateur stargazers using standard telescopes. NASA also plans to stream the images live on its website.(dpa)