Cluster's Last Stand?

PARIS--The European Space Agency (ESA) appears to have found a way to salvage its Cluster mission, the four-probe mission to study Earth's magnetosphere that blew up shortly after launch last June. At a meeting here this week of ESA's Science Program Committee, the French firm Arianespace, which built the ill-fated rocket, proposed that Cluster-2 be launched on Russian Soyuz rockets. That would cut the cost of the mission enough so that it just might be affordable. Says ESA spokesperson Simon Vermeer, "Cluster isn't dead yet."

Hard hit by recent budget cuts, ESA has put off future space programs to liberate the $244 million needed to fly four new identical Cluster probes. But none of the major partners (France, Germany, and the U.K.) is willing to foot an additional $27 million to rebuild Cluster's scientific payload. And Arianespace says that it would cost more than ESA has budgeted to launch the new Cluster probes on two old Ariane 4 rockets.

Instead, Arianespace says the agency would save a considerable--but as yet unknown--amount of money by entrusting the payload to its new Starsem joint venture with the Russian Space Agency, which builds the Soyuz rockets. The move would allow ESA to use some of its science budget to underwrite the scientific instruments that individual countries won't shell out for. "The absolute condition is that we will not exceed the 'envelope' of [$244 million]," says Serge Volonté, ESA's astronomy missions coordinator.

A final decision on the scheme will be made at a 3 April meeting. Even if the full-scale mission bites the dust, one Cluster probe, Phoenix--the "spare" that didn't make the ill-fated first flight--will be piggybacked on another Ariane payload to orbit without its fellows.