August 30, 2006. Copyright 2006. Graphic News. All rights reserved.


Death plunge on to Moon ends SMART mission


LONDON, August 30, Graphic News: EuropeÕs first probe to the moon will come to a dramatic end on Sunday when it smashes at 7,000km/h (4,365mph) into the nearside of the lunar surface.

The crash should happen at approximately 05:42GMT as the SMART-1 (Small Mission for Advanced Research in Technology) spacecraft impacts on a volcanic plain called the Lake of Excellence on the southwest of the Moon's disc. But the impact might occur one orbit (about 5 hours) earlier if the low-flying spacecraft happens to hit a mountainside.

ÒIt will be a very shallow trajectory,Ó mission scientist Professor Bernard Foing said. ÒItÕs possible that much of the probeÕs structure will be preserved from the impact, accidentally creating a sculpture or a monument for future generations which says Ôthere you are, that was EuropeÕs first attempt to explore the MoonÕ.Ó

Since SMART-1 was placed into orbit in September 2003 it has been powered only by the eerie blue glow of its futuristic ion drive. This is a form of continuous low-thrust engine that uses electricity derived from solar panels to produce a beam of charged particles that pushes the spacecraft forward. Such engines are commonly called ion engines, and are considered essential for future, long-range space missions. 

This is only the second time that ion propulsion has been used as a missionÕs primary propulsion system; the first was NASAÕs Deep Space 1 probe launched in October 1998. The ion drive is the dream of a high school physics lesson. It takes the theory of Isaac NewtonÕs third law of motion: ÒFor every action, there is an equal and opposite reactionÓ; adds the frictionless vacuum of deep space; and then uses the concept of a TV cathode ray tube with the screen cut off to spew out a beam of ionised gas, exerting no more force than a sheet of paper resting on the hand.

As solar panels of a normal size supply only a few kilowatts of power, a solar-powered ion engine cannot compete with the blast of a chemical rocket. But a typical rocket burns for only a few minutes. An ion engine can go on pushing gently for months or even years -- for as long as the sun shines and the small supply of propellant lasts. 

The spacecraft has now orbited the Moon more than 2,000 times, mapping minerals in the lunar surface. Its cameras have beamed back the best digital maps of the Moon ever made, revealing features as small as 40 metres (130ft) across.

Analysis of the observations will help scientists piece together the history of the Moon, and determine whether it first formed when a Mars-sized body slammed into Earth, spewing debris into space. ÒThatÕs the best theory in town by a long way,Ó says team member Manuel Grande from the University of Wales in Aberystwyth.
/ENDS

Sources: ESA, NASA