Scientists get spare parts for Cluster's next stand

A replacement for the space mission Cluster could be in the skies as early as next summer, in a slimmed-down form. Cluster II, whose predecessor exploded just after being launched earlier this month, would be a shadow of its former self - containing just one spacecraft rather than the original four.

A senior European Space Agency committee met last Friday to discuss salvaging the Cluster mission, which was to have probed the effect of the solar wind on the earth's magnetic field. As a fleet of four identical spacecraft it would have monitored phenomena from four different points.

At a further meeting next week, the space science committee will vote on whether to send up just one spacecraft instead. A rummage round European laboratories over the past few weeks has shown that there are sufficient spare parts to build one satellite and all its 11 instruments.

"There is quite a lot of pressure to do that," said Mike Cruise, professor at Birmingham University and a UK member of the space science committee. The cost would be about Ecu30 million (Pounds 24 million), equivalent to two years' raiding of the ESA director's contingency funds.

"I feel there is a good justification for this," said Professor Cruise. "Cluster was always going to be part of an international programme involving many other spacecraft and in a sense ESA is letting down its collaborators in the United States and Japan."

But many space scientists have said over the past few weeks that to send up one spacecraft would be almost useless. The virtue of Cluster was its four points of view. Yet a carbon copy of the the original Cluster would cost ten times more than putting the single replacement into space. It would mean that another ESA medium-term mission might have to be cancelled or postponed for several years.

A decision on whether a Cluster replacement should be more ambitious will be made in the early autumn. There are two principal possibilities. One is to create three more identical satellites and send them up into the same orbit as the single replacement.

The second possibility is to send up three smaller satellites, of which the UK would probably build one. To achieve this, space scientists would ask industry to fund Cluster II to test small satellite technology.