No advance warning of an impending collision

Iridium Satellite LLC said it had no advance warning of an impending collision between one of its communications satellites and a defunct Russian military satellite above Siberia. Amid questions of liability, negligence and possible lawsuits, the closely held company rejected suggestions that it might have come to disregard "conjunction reports" - potential accident alerts - routinely relayed by the US military.

"Iridium didn't have information prior to the collision to know that the collision would occur," said Liz DeCastro, a company spokesman. "If the organisations that monitor space had that information available, we are confident they would have shared it with us."

She was responding to questions about an 18-month-old presentation by retired US Air Force General John Campbell, Iridium's executive vice president for government programmes. Iridium had been receiving a weekly average of 400 conjunction reports from the US Strategic Command's Joint Space Operations Centre that tracks debris in space, General Campbell told a June 2007 forum hosted by the George C. Marshall Institute, a Washington research group.

"So the ability actually to do anything with all the information is pretty limited," he said, describing a kind of data overload. The conjunction reports were issued every time a potential threat object was to pass within five kilometres of a commercial satellite, he said.

"Even if we had a report of an impending direct collision, the error would be such that we might manoeuvre into a collision as well as move away from one," he told the panel.

Gen. Campbell then endorsed the so-called "Big Sky" theory - that space is so vast that the chances of a collision are infinitesimal, despite more than 18,000 pieces of orbiting junk big enough to track.

"We figure that the risk of a collision on any individual conjunction is about one in 50 million," he said at the time, adding: "Clearly that risk is something bigger than zero."

Marine Corps General James Cartwright, vice chairman of the Joint Chiefs of Staff and a former head of the command that runs US military space operations, said countries with satellites in space will have to play "dodgeball" for decades to avoid debris from the collision. It occurred about 485 miles above the Russian Arctic on Tuesday.