NASA will take a giant step toward bringing humans back to the moon on Tuesday as a new orbiting satellite arrives there to search for water.
The Lunar Reconnaissance Orbiter (LRO) is expected to reach the moon's orbit at 0943 (GMT).
The LRO will send back data to help scientists find the best location for a manned landing. The question of whether there is water on the moon, in the form of ice deep inside lunar craters, is key to the mission.
The new lunar mission is to pave the way for the next stage of the US space programme - building a base on the moon as a launch pad for further space exploration. In 2010, NASA is to retire the 28-year-old shuttle programme which has helped to build the orbiting space station. The new moon-bound spacecraft Orion is to be ready by 2015.
The LRO is the first stage of a two-part mission launched on a single rocket on Thursday. When the LRO reaches the moon early Tuesday it will enter an elliptical orbit so its seven-instrument payload can be tested. After about 60 days, it will move into a low orbit over the moon's poles to conduct its observations.
The second part, the Lunar Crater Observation and Sensing Spacecraft (LCROSS), will circle the Earth for about four months before crashing into a permanently dark crater on the lunar surface, kicking up a cloud of dust that can be analyzed to see if it contains water.
{{/usCountry}}The second part, the Lunar Crater Observation and Sensing Spacecraft (LCROSS), will circle the Earth for about four months before crashing into a permanently dark crater on the lunar surface, kicking up a cloud of dust that can be analyzed to see if it contains water.
{{/usCountry}}The LCROSS separated from the LRO craft shortly after lift-off on Thursday to follow a different course. Along with a piece of the Atlas rocket that boosted it into space, it is to enter into an elongated, sweeping orbit that will take it around the Earth and moon for the next four months.
In October, LCROSS and its rocket piece are to slam into a dark crater near a lunar pole, kicking up a cloud of debris more than 10 km above the surface.
NASA hopes that if debris from the shadowed crater contains ice, hydrocarbons or other organic materials, it will vaporize when it hits sunlight.