Scientists aware satellite paths would be close

By Tim Hepher

PARIS (Reuters) - European space scientists were aware of the potential for a close encounter between Russian and U.S. satellites before they crashed.

But the difficulty of predicting orbits and "noise" from thousands of pieces of debris made a definitive prediction of a collision impossible, European officials said on Thursday.

"The 'catalogue' of objects and debris showed a possible approach between the paths of the two satellites but an approach doesn't necessarily mean a collision, and you would need more information to be certain," said Philippe Goudy, deputy director of the French space operations control center at Toulouse.

"It is not a case of two satellites coming together out of nowhere; they had been followed. The U.S. catalogues can give an alert but these are not necessarily completely exact."

Washington reported the first collision of its kind, between a privately owned U.S. communications satellite and a defunct Russian military satellite, on Wednesday.

Each day, officials at the Toulouse center, operated by France's CNES space agency, examine catalogues of radar tracking data supplied to the world's space-faring nations by U.S. Space Command, the only steady source of orbital mapping information.

"What we do for the 15 satellites we control is to watch them every day in orbit and we verify whether there is an alert. If so, we look for more radar information," Goudy told Reuters.

The crash occurred on Tuesday 485 miles above the Arctic in a crowded polar orbit used by satellites that monitor weather, relay communications and perform scientific surveys.