If all goes well, the European Space Agency's unmanned SMART-1 will be captured by the Moon's gravity at 1748 GMT on Monday, nearly 14 months after launch from Europe's space base in French Guiana.

Several weeks later, the probe will make final adjustments so that it is placed in an egg-shaped orbit, looping around the Moon's poles and enabling its package of scientific sensors to be fired up for a six-month remote exploration of the lunar surface.

"Europe is now reaching the final gateway to the Moon," Bernard Foing, ESA's chief scientist and lead scientist behind the SMART-1 project, said last week.

"(It is) a journey to the origins of Earth and Moon, and a step towards future exploration."

The spacecraft is a testbed of exciting miniaturisation technologies, including an ion engine -- a sort of solar-powered thruster that is many times more efficient than conventional chemical rocketry.

Solar panels convert sunlight into electricity and use it to electrically charge atoms of heavy gas.

These ions are then spewed out at high velocity from the spacecraft, enabling it to move forward.

SMART-1's wee engine is not fast but it is certainly miserly.

A year after its launch, the engine had operated for about 3,300 hours and covered some 78 million kilometers (49 million miles), but sipped just 52 kilos (114 pounds) of propellant, scientists said.

That sort of efficiency would make ion power the ideal thrust for sending unmanned probes into the deepest corners of the Solar System, to Saturn, Uranus, Neptune and beyond.

Time is not a big factor in these years-long missions, but payload is. The less fuel that has to be carried, the more mass can devoted to scientific instruments.

The 19-kg (42-pound) cargo of seven instruments carried by SMART-1 is similarly groundbreaking.

It is designed to test new communications technologies and answer nagging questions that remain about the Moon, more than 30 years after the last Apollo mission there.

Among the puzzles is what exactly the Moon is made of, how it originated and whether -- contrary to conventional views that have the lunar surface depressingly arid -- there could still be water ice lurking in craters near the poles.

If water is found in significant quantities, that would be vital for setting up a human colony on the Moon.

SMART-1 carries an X-ray spectrometer, designed to make the first-ever global X-ray map of the Moon's surface, and a laser communicator, to send data packages back to Earth at the speed of light.

Laser technology is commonly used for communications by satellites that orbit Earth in geostationary positions. SMART-1's use will mark the first time, though, that lasers have been successfully used this way by a rapidly moving, distant spacecraft.

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