November 16, 2004. Copyright 2004. Graphic News. All rights reserved.

EuropeÕs first moon probe goes into lunar orbit

LONDON, November 16, Graphic News: EuropeÕs first probe to the moon has entered orbit around our closest neighbour, powered only by the eerie blue glow of an ion engine.

The 367kg (809lb) spacecraft, SMART-1 (Small Mission for Advanced Research in Technology), blasted off in September 2003 atop an Ariane V launcher. After a 16-month journey SMART-1 has now reached its destination and will become a science platform to carry out studies of the moon.

ÒSMART-1 will search for signs of water-ice in craters near the moonÕs poles, provide data to shed light on the still uncertain origin of the moon, and reconstruct its evolution by mapping its topography and the surface distribution of minerals and key chemical elements,Ó announced ESA.

In its role as technological demonstrator, SMART-1Õs primary goal is to test its futuristic ion drive, which Europe has used for the first time as its main spacecraft propulsion. 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. 

ÒThis is the first European mission to the moon, this is the first smaller, faster mission and this is the first solar-powered spacecraft,Ó said Professor Manuel Grande, of the Rutherford Appleton Laboratory in Oxfordshire.

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 chemical 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. 

On Monday, SMART-1 began firing its ion engine to bring it into lunar orbit after travelling some 400,000km (248,500 miles) from Earth.

Continuous engine firing over the next four days should push the probe over a ÒhumpÓ, beyond which it will be captured by the MoonÕs gravity. After this, it will spiral closer to the surface until it enters into a near-polar orbit in January 2005.
/ENDS

Sources: ESA, NASA