Washington  - In the 40 years since the first man set foot on the moon, NASA has turned its attention away from Earth's nearest celestial neighbour to look ever deeper into space and build an orbiting space station.

But much remains mysterious about the moon, and NASA hopes to clear up some of the remaining questions with dual missions designed to set the course for the resumption of human lunar exploration.

The Lunar Reconnaissance Orbiter (LRO) and Lunar Crater Observation and Sensing Satellite (LCROSS) are to launch aboard a single rocket on June 17. Together they will send data back to NASA to help scientists find the best location for a spacecraft landing to again bring humans to the moon.

The moon 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.

The LRO will orbit the moon, 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.

"We have much better maps of Mars than we have of our own moon's polar regions," said Craig Tooley, project manager for the 504- million-dollar LRO mission.

He told reporters that while the Apollo missions stayed near the moon's equator, the lunar poles are the likely landing targets for a potential manned spacecraft.

The LRO will orbit the moon for about a year to develop the maps, before turning its attention to other scientific endeavours being proposed by scientists.

"LRO will bring new eyes to the moon and with these eyes we'll see new views of the moon," said Rich Vondrack, a project scientist on the mission.

Its eyes consist of seven instruments pointed at narrow sections of the moon which will gradually capture the entire surface. It will pay special attention to 100 regions of high interest.

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.

NASA scientists said that it is possible for frozen water to have remained in the moon's craters for billions of years, because the bottoms of the craters are never reached by sunlight and protect any ice from evaporation into the moon's thin lunar atmosphere.

After launch, the rocket will deliver the LRO into orbit around the moon, then take a long loop around the moon and earth still carrying the LCROSS satellite.

The manoeuvre is designed to properly position LCROSS to crash into the moon around 110 days later, around October 7-11. LCROSS is to separate into two parts that will crash into a dark crater. The first part will send up a cloud of dust to be measured by a second, trailing device that will 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)