A dishwasher-sized spacecraft on Europe's first mission to the moon was set to enter lunar orbit, a key milestone in its 13-month trip into space, the European Space Agency said.
The SMART-1 probe was to begin circling the moon sometime overnight Monday to Tuesday in a new phase after spiraling around the Earth for more than a year, ESA spokesman Franco Bonacina said.
The spacecraft is expected to explore the moon's surface for at least six months, looking for water and helping scientists study the idea of building a permanent base on the lunar surface. The probe is to begin examining the moonscape in January.
The body of the 809-pound probe measures 3.3 feet on each side. Its solar panels, which help provide ion — or solar-electric — propulsion, spread 46 feet.
The SMART-1, billed as a test bed for fuel efficient technologies, is carrying only about 176 pounds of xenon fuel. More traditional rockets can require tons of fuel.
"This is a sort of test for ion propulsion," Bonacina said. "It has the potential to be used for longer missions in the future — to travel to other planets, for example."
Though other methods of propulsion are faster for relatively short distances — such as from Earth to the moon — ion propulsion should prove to be faster for longer missions, he said.
The mission marks the second time that ion propulsion has been used as a primary propulsion system. The first was the Deep Space 1 probe launched by NASA in October 1998.
SMART-1, short for "Small Missions for Advanced Research and Technology," was developed for ESA by the Swedish Space Corporation with contributions from some 30 contractors in Europe and the United States. It took off aboard an Ariane-5 rocket in September 2003.
The total cost for the mission is $142.3 million, about a fifth of that required for a typical major space mission.