In an unprecedented collision in space, two huge satellites slammed into each other nearly 500 miles above Siberia, creating a debris field that likely will pose a danger to other man-made objects.
Experts at NASA said the collision on Tuesday between a 1,200-pound American-made Iridium commercial satellite and a 2,000-pound Russian satellite poses a small but elevated risk to the international space station, which is in an orbit about 270 miles below the collision.
Other experts said the 20-year-old Hubble Space Telescope may be in more danger.
There should be no risk to the space shuttle set to launch with seven astronauts on Feb. 22, officials said, but the danger will be re-evaluated close to the launch date.
Experts did not have any idea Wednesday night of the size of the debris field or the number of pieces in it.
"As of about 12 hours ago, I think the head count was up to 600 pieces," he told CBS News.
The American communications satellite was launched in 1997. The Russian satellite was fired into space in 1993 and was not believed to be functioning.
The threat of a destructive impact between the space station and pieces of the shattered satellites is comparable to the threat of a debris strike caused by China's surprise anti-satellite weapons test in January 2007, NASA spokesman Kelly Humphries said.
"So far, the risk appears to be elevated but still very small," he said.
The unannounced Chinese test, which involved a missile aimed at a defunct low altitude satellite owned by the Beijing government, created an outcry of protest worldwide but caused no harm to the space station in the two years that followed.
NASA's Mission Control, which has its own team of debris analysts, is prepared to order an avoidance maneuver if military trackers judge the orbital facility to be at risk from debris.
NASA's flight controllers could call for a maneuver if a large piece of the debris were to cross through a protective zone about 30 miles ahead, behind and to either side of the fast-moving space station.
Station commander Mike Fincke, astronaut Sandy Magnus and Yuri Lonchakov of Russia were notified of the collision, officials said.
According to the Union of Concerned Scientists, 115 nations currently operate 905 satellites in Earth orbit.
The largest hazard of collision, however, is posed by a growing population of debris from satellite launches and derelict satellites.
The military routinely tracks about 18,000 objects in space, including satellites and large pieces of debris.
Iridium Holdings LLC has a system of 65 active satellites that relay calls from portable phones that are about twice the size of a regular mobile phone.
It has more than 300,000 subscribers. The U.S. Department of Defense is one of its largest customers.
The company said the loss of the satellite was causing brief, occasional outages in its service and that it expected to have the problem fixed by Friday, according to the Associated Press.
There was no comment from the Russian space agency Wednesday night.