MOSCOW, Feb 12 (Reuters) - Space officials in Russia and the United States were on Thursday tracking hundreds of pieces of debris that were spewed into space when a U.S. satellite collided with a defunct Russian military satellite.
The crash, which Russian officials said took place on Tuesday at about 1700 GMT above northern Siberia, is the first publicly known satellite collision and has raised concerns about the safety of the manned International Space Station.
"We believe it's the first time that two satellites have collided in orbit," said Air Force Colonel Les Kodlick of the U.S. Strategic Command.
He said the debris from the collision between a spacecraft operated by the Iridium Satellite LLC and a Russian Cosmos-2251 military satellite was potentially a problem that could require more debris-avoidance manoeuvres among space-faring nations.
The crash occurred 485 miles (780 km) above the frozen wastes of the Russian Arctic, an altitude used by satellites that monitor weather, relay communications and perform scientific observations.
"It's a very important orbit for a lot of satellites," Kodlick said.
The U.S. Joint Space Operations Center was tracking 500 to 600 new bits of debris, some as small as 4 inches (10 cm) across, in addition to the 18,000 or so other man-made objects it previously catalogued in space, he said.
Russian Space Forces said it was monitoring debris that was spread over altitudes between 500 km and 1300 km above earth.
The priority is guarding the International Space Station, which orbits at 220 miles (350 km), substantially below the collision altitude.
The orbit of the ISS can be changed by controllers from Earth but even a tiny piece of debris can cause significant damage to the space station as it travels at 8 km per second.
"If there is any threat to the ISS then there will be an announcement," one Russian space official said. Another said there was little immediate threat to the station.
The crash has underlined concerns about how crowded the orbit paths around the planet have become in recent decades.
Nicholas Johnson, an orbital expert at NASA's Johnson Space Center in Houston, said it was uncertain how much new debris had been created by the crash.
"It takes a while for the debris to spread out and for us to get an accurate head count," he said. NASA receives orbital tracking services from the Defense Department and regularly manoeuvres its spacecraft to avoid debris.
Among the 18,000-plus objects being tracked in space by the U.S. Strategic Command are operational and defunct satellites, spent rocket boosters and debris.
Bethesda, Maryland-based Iridium said the U.S. satellite was shaped like a box with wings and weighed about 1,300 pounds (600 kg). The Russian craft, a barrel-shaped cylinder with a mass of 1,800 to 1,900 pounds (800 to 850 kg), was launched in June 1993 and stopped working in 1995, Russian Space Forces said.
Iridium operates the world's largest commercial satellite constellation made up of some 66 cross-linked satellites plus orbiting spares. It provides voice and data services for areas not served by ground-based communications networks.
The operation remained healthy, though some customers may experience brief outages pending a temporary fix expected to be in place by Friday, said Liz DeCastro, an Iridium spokeswoman.
She said Iridium planned to move one of its in-orbit spare satellites into the constellation to replace the lost craft within 30 days. (Additional reporting by Tatiana Ustinova in Moscow and Jim Wolf, Irene Klotz and Andrea Shalal-Esa in Washington; editing by Diana Abdallah)
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