BEIJING, Sept. 4 -- Europe's first spacecraft to the moon ended its three-year mission yesterday with a planned crash on the lunar surface, hitting its target at 2 kilometres per second, or 7,200 kilometres per hour.

The impact, in a volcanic plain called the Lake of Excellence, was captured by observers on Earth, and scientists hope the resulting cloud of dust and debris would provide clues to the geologic composition of the site.

"That's it we are in the Lake of Excellence," said spacecraft operations chief Octavio Camino as applause broke out in the European Space Agency's mission control centre in Darmstadt, Germany. "We have landed."

Minutes later, a video screen on the control room wall showed an image of the bright flash from the impact. The infrared image was captured by the Canada France Hawaii Telescope on Mount Kea, in Hawaii.

"It was a great mission and a great success and now it's over," said mission manager Gerhard Schwehm.

During its months in orbit around the moon, the spacecraft scanned the lunar surface from orbit and took high-resolution pictures. But its primary mission was testing a new, efficient, ion propulsion system officials hope to use on future interplanetary missions including the BepiColombo mission to Mercury slated for 2013.

SMART-1 Small Mission for Advanced Research and Technology was launched into Earth orbit by an Ariane-5 booster rocket from Kourou, French Guiana, in September 2003. It used its ion engine to slowly raise its orbit over 14 months until the moon's gravity grabbed it.

The engine, which uses electricity from the craft's solar panels to produce a stream of charged particles called ions, generates only small amounts of thrust but only needed 80 kilograms of xenon fuel.

Ground controllers learned to adjust to the slow but continuous acceleration from the ion engine, requiring them to check the craft's course more often than with the one-time push from a rocket. US astronauts on Apollo missions flew to the moon in just three days, launched by giant Saturn-V rockets.

SMART-1's X-ray and infrared spectrometers have also gathered information about the moon's geology that scientists hope will advance their knowledge about how the moon's surface evolved and test theories about how the moon came into being. Although the moon has been explored by astronauts in several places, the new data covers the moon's surface as a whole.

On Saturday, mission controllers had to raise the craft's orbit by 600 metres using its positioning thrusters to avoid hitting a crater rim on final approach. Had the orbit not been raised the craft would have crashed one orbit too soon, making the impact difficult or impossible to observe.

The manoeuvre had to be carried out quickly in the early hours of Saturday and operations chief Camino admitted that "we were under some stress."

SMART-1, a cube measuring roughly a metre on each side, took the long way to the moon more than 100 million kilometres instead of the direct route of 350,000 to 400,000 kilometres. But ESA did it for a relatively cheap 110 million euros (US$140 million).

The spacecraft has also been taking high-resolution pictures of the surface with a miniaturized camera, sending back its last close-up images just minutes before the impact.

(Source: China Daily)