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Mirror in the sky: will Ariane give it a safe lift-off? Credit: ESA

Concerns over the possible failure of the launch of an X-ray satellite on Europe's new Ariane 5 rocket, scheduled for December, have led the European Space Agency (ESA) to consider taking out insurance on a scientific payload for the first time.

Fears for the X-ray Multi-Mirror (XMM) mission surfaced at ESA's science programme committee last week (see opposite), when the question of whether payloads should be insured was discussed.

Originally XMM was to have been the ninth launch on Ariane 5. But postponements by other customers of Arianespace, the company that administers Ariane launches, have brought XMM forward to the fourth launch of a vehicle that does not yet have an established track record.

Ariane 5's maiden flight was a disaster, exploding after lift-off and destroying ESA's Cluster mission (see Nature 381, 541; 1996). Arianespace has since conducted two more validation launches. The first, dogged by problems, placed its payload in the wrong orbit. The second was a success.

Ken Pounds, professor of space physics at Leicester University, says he is not aware of unusual concerns among researchers about a launch failure. “Most people assume XMM will have the usual more than 90 per cent chance of getting into the right orbit,” he says. But Pounds acknowledges that it is “not usual” for a science mission to be insured.

The insurance premium might be found from XMM's budget of 671 million euros (US$700 million). Payload instruments supplied by national agencies are worth a further 171 million euros. Given the tensions that arise within ESA over the supply of such payloads, it may consider it worth insuring against their loss.

Meanwhile those responsible for the mission are looking closely at reports of problems with some of the detectors on the US space agency NASA's equivalent telescope, Chandra, launched in July. The front-side illuminated chip of the imaging spectrometer, ACIS, has been suffering from degradation, perhaps from the impact of soft protons that have penetrated the telescope's shield.

Martin Weisskopf, project scientist for Chandra, says NASA has been working closely with ESA and with researchers who may be affected by the problem. So far, the only effect appears to be a reduction in the efficiency of the telescope. “Our mission is not impaired,” he says. “It is not a crisis, [although] it is annoying and a nuisance.”

But Pounds says his group is studying Chandra's performance “keenly”. He adds: “We need to satisfy ourselves that there is no parallel danger for XMM, and ensure we are not vulnerable to similar problems.”

NASA is still working on the source of the problem. One theory is that the damage results partly from Chandra's deep-space orbit. This brings it into contact with the Earth's outer radiation belts, in particular the Van Allen belt, which consists of high-energy electrons, protons and other energetic particles.

ACIS may have been damaged by particles passing down the telescope while in this belt. NASA has removed the instruments from the focal plane of the telescope during this period. Weisskopf says the degradation has ceased.