May 24, 1996. Copyright, 1996, Graphic News. All rights reserved

COUNTDOWN FOR CLUSTER
By Laura Spinney, Science Editor

LONDON, May 24, Graphic News- The countdown to the maiden flight of EuropeÕs newest satellite launcher has started. Barring delays due to last minute checks or bad weather conditions, Ariane 5 is scheduled to take off from Kourou in French Guiana around noon on Thursday May 30.

The launcherÕs first mission will be to carry the four identical Cluster satellites into geostationary orbit above the Earth. The satellites have been supplied by the European Space Agency as part of its contribution to the Solar-Terrestrial Science Programme (STSP), a joint project with NASA. Over the next two years, Cluster will collect data on the dynamic relationship between the magnetic field surrounding the Earth and solar winds. 

Electrically charged winds generated by the sun can travel towards Earth at speeds of up to three million kilometres per hour. The EarthÕs magnetosphere offers some protection, but occasionally those winds distort or even tear the magnetic shield giving rise to atmospheric phenomena such as the aurorae Š the spectacular light shows that occur naturally in the skies above the EarthÕs poles.

Until now, exploratory satellites have probed the magnetosphere alone or in pairs, sometimes producing ambiguous data. Once released into orbit, the Cluster satellites will fly in tetrahedral formation Š hence their name. With the same measuring instruments on board each, the idea is that their simultaneous observations will for the first time provide a three-dimensional picture of the aurorae and other phenomena of the EarthÕs plasma environment. Scientists at STSP hope that the Cluster data will enable them to make predictions about Ōspace weatherÕ that, among other things, could help prevent damage done to communications satellites by solar gusts.

All tests of the satellites are now complete, according to Ray Merchant of Matra Marconi Space UK, a predominantly French company that has been involved in developing ClusterÕs steering and propulsion systems. ŌThe satellites have been loaded on to the launcher in the last week, and Ariane 5 looks set to take off on time,Õ he says.

Sources: European Space Agency, Matra Marconi Space UK Ltd