Heavens saved from bad waves

三月 31, 2000

The imminent destruction of the 66 Iridium satellites - possibly the most expensive firework display in history - will be watched with particular glee by radio astronomers.

The global telephone network had long been threatening to flood the skies with radio waves from callers all over the world, which would have swamped signals from distant stars and galaxies.

It put at risk exploration of the heavens by experts from several university groups in the United Kingdom, which began shortly after the end of the second world war with the pioneering work of people such as Sir Bernard Lovell.

It seems the nightmare is over, however, with the announcement by part-owners Motorola that following Iridium's bankruptcy it would start to "de-orbit" the 66-strong fleet of satellites into the Pacific Ocean in less than a fortnight.

Ian Morison, a radio astronomer at the University of Manchester's Jodrell Bank observatory in Cheshire, said: "We were very worried before - shall we say that we're not unhappy now."

In fact, the unpopularity of the Iridium telephones - overshadowed in Europe in particular by the explosion of cell phones - meant that the disruption so far has been minimal.

Radio astronomers had feared the worst, particularly when they found that Iridium would be using wavelengths catastrophically close to a key part of the electromagnetic spectrum in which signals from common hydroxyl ions can be detected. This is important when studying phenomena such as star death.

Paul Scott, a scientist at the Mullard Radio Astronomy Observatory, University of Cambridge, said that although his work had been unaffected by Iridium, it had caused much bad feeling within the scientific community for the way in which the companies involved had tried to ignore the concerns of astronomers.

"We're very pleased with what has happened, but it was disgraceful that it was allowed to get to this stage," he said.

The clamour raised by radio astronomers forced Iridium to sign a deal with the European Science Foundation in June last year to limit its pollution of the hydroxyl wave band within six years.

However, even with its demise, the radio astronomers are still wary that there may be further intrusions into their heavens - other large-scale communications satellite constellations are being planned.


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