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Lunar probe set to crash
31/08/2006 10:57 - (SA)
Berlin - Europe's first mission to the moon is due to crash-land in a cloud of dust and rock on Sunday, ending a three-year voyage that gathered data about the lunar surface and tested a new engine intended to propel future spacecraft to other planets.
The European Space Agency's Smart-1 should hit its target on a volcanic plain called the Lake of Excellence at 05:41 GMT, orbiting lower and lower as it makes its final approach at two kilometres per second.
Observatories on Earth will try to capture images of the impact and the resulting debris cloud, and European space officials hope their study of the debris will provide information about the minerals present at the impact site.
Even before the mission ends, however, ESA is already celebrating the main goal - a successful test of the ion engine they hope to use for future interplanetary missions, such as the BepiColombo joint mission to Mercury with Japan's space agency slated for launch in 2013.
"The prime object of this mission was to test the ion propulsion," mission manager Gerhard Schwehm said.
"This is a very efficient means to get a spacecraft over large distances with a very small mass of fuel. It worked really well."
Instead of burning rocket fuel, the PPS-1350 engine generates electrically charged atoms called ions. That creates minuscule amounts of thrust.
Riding that small, steady push, Smart-1 made it to the moon in 14 months, gradually accelerating and raising its orbit around the Earth until it was high enough to be grabbed by the moon's gravity.
Valuable information
It was launched into Earth orbit using an Ariane-5 rocket from the European spaceport in Kourou, French Guinea, on September 27, 2003.
By contrast, the first manned US moon mission, Apollo 11, took 76 hours to reach lunar orbit in 1969.
Smart-1, a cube measuring roughly a metre on each side, took the long way - over 100 million kilometres instead of the direct route of 350 000 to 400 000 kilometres.
But ESA did it for a relatively cheap $140m and on only 80kg of xenon fuel. Nasa's Deep Space 1, launched in 1998, also used an ion engine.
ESA flight controllers and scientists at mission control in Darmstadt, Germany, honed their skills in managing the different rhythm of spaceflight with ion propulsion, where the continuous thrust requires more careful monitoring than coasting after the one-time impulse from a rocket.
Although the moon has already been explored by US astronauts, ESA says Smart-1 gathered valuable information as it orbited.
Its miniaturised X-ray and infrared spectrometers probed the mineral content of the surface to better understand the distribution of elements over the entire moon, not just the small areas explored by astronauts.
The information could increase scientists' understanding of how the moon's surface evolved and help test a theory that the moon originated when another astronomical body slammed into Earth.
On the net:
sci.esa.int
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