Two satellites collide 500 miles over Siberia

— -- Two communications satellites collided Tuesday in an unprecedented orbital accident that would have been visible from the Earth, a NASA scientist said Wednesday.

The collision roughly 500 miles from Earth created a huge field of debris, but the risk to the International Space Station and its crew of three — 215 miles from Earth — is very low, said Nicholas Johnson of NASA's Johnson Space Center. So is the risk to the next shuttle mission, he said. The launch is scheduled for as early as Feb. 22.

The debris, though, could make it more dangerous for astronauts to repair the Hubble Space Telescope on a space shuttle mission planned for May, Johnson said. The Hubble is about 375 miles from Earth, Johnson said, and debris generally falls toward Earth.

The collision was between a now-defunct Russian communications satellite launched in 1993 and one of 66 satellites privately owned by Iridium, a Maryland company that provides phone service to customers such as workers on offshore oil platforms. The company said in a statement that service interruptions should be minimal and fixed by Friday.

The collision, which occurred at about noon ET Tuesday, "was dramatic, and it has significant consequences for the (space) environment," Johnson said. "This was the worst such incident that's ever occurred."

The spacecraft collided over northern Siberia, where it was evening at the time. A "flash" would have been visible from the ground, Johnson said.

The hundreds, if not thousands, of pieces of debris created by the collision could damage other working satellites, he said. Especially at risk are other Iridium satellites, which are "right there in the heart of the cloud."

Although the U.S. military and others track orbital objects, there is no way to prevent them from running into each other. Such collisions are rare, however.

"Space is a big place. The odds are very small that something like this would happen," Johnson said.

"There are no rules of the road in space," he said. "Anyone can be anywhere they want to be."