Europe's first spacecraft to the moon ended its three-year mission Sunday with a planned crash, hitting its target after ground controllers had to maneuver it around a looming crater rim.
The SMART-1 spacecraft slammed into volcanic plain called the Lake of Excellence at 1.2 miles (2 kilometers) per second right on time. The impact was captured by observers on Earth, and scientists hoped 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," spacecraft operations chief Octavio Camino said as applause broke out in the European Space Agency's mission control center in Darmstadt. "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.
Testing ion propulsion
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 that officials hope to use on future interplanetary missions, including the BepiColombo mission to Mercury slated for 2013.
SMART-1 was launched into Earth's 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 176 pounds (80 kilograms) of xenon fuel. Such an engine was tested on NASA's Deep Space 1 spacecraft.
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 in contrast to the one-time push from a rocket. U.S. astronauts on Apollo missions flew to the moon in just three days, launched by giant Saturn 5 rockets.
The craft's X-ray and infrared spectrometers have 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.
Stressful maneuver
On Saturday, mission controllers had to raise the craft's orbit by 2,000 feet (600 meters) 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 maneuver had to be carried out quickly in the early hours of Saturday, and operations chief Camino acknowledged that "we were under some stress."
Slideshow 12 photos
Month in Space: January 2014
SMART-1, a cube measuring roughly a yard (meter) on each side, took the long way to the moon — more than 62 million miles (100 million kilometers) instead of the direct route of 217,000 to 250,000 miles (347,000 to 400,000 kilometers). But ESA did it for a relatively cheap $140 million.
The spacecraft 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.
Amateur astronomers as well as professionals watched for the impact using ground-based telescopes from South Africa to the Americas to Hawaii. However, it took specialized equipment to catch the flash, and observers with garden-variety telescopes generally missed the show.
Bruce Betts, director of projects for the nonprofit Planetary Society, said the impact was just "the icing on the cake" for a successful lunar mission. "It went out with a bang," he said from the society's California headquarters.
This report was supplemented by information from MSNBC.com's Alan Boyle.