NASA says satellite collision, Chinese test behind flood of space debris

A February collision of Iridium and Russian communication satellites and the destruction in 2000 of a Chinese satellite are the likely sources of much of the space debris that have been hurtling precariously close to the International Space Station in recent weeks, according to NASA.

The crews of the space station and the space shuttle Discovery yesterday had to maneuver the two crafts out of the path of a four-inch piece of the Chinese satellite that was moving quickly toward them. NASA officials feared that the debris would have come too close for comfort to the locale of today's already dangerous spacewalk by two NASA astronauts.

The Discovery docked with the International Space Station last Tuesday.

This is the third time in little more than a week that space junk has come close enough to the space station to pose a potential risk to the crew and the orbiter. The space station crew was on alert early last week before a four-inch piece of a defunct Russian satellite ultimately flew harmlessly by on Tuesday morning. And late the week before, the two U.S. astronauts and one Russian cosmonaut aboard the station were forced to seek shelter in the attached Soyuz TMA-13 Capsule when a piece of an old rocket motor came dangerously close.

"There's definitely more debris up there," NASA spokesman Bill Jeffs said today. "That collision means more debris will make its way down to the lower orbit [where the space station is]. It's adding a lot of particles up there."

Last month, the Iridium communication satellite collided with a Cosmos 2251 Russian government communication satellite. Jeffs said the Russian satellite was believed to be nonoperational at the time of the crash, which knocked out the Iridium satellite.

The collision happened about 491 miles over Siberia. The orbit of the space station -- and for the duration of the current mission, the orbit of the space shuttle as well -- is about 220 miles above the Earth. That means as the debris slowly falls into lower orbits, it will increasingly litter the space around the space station.

Jeffs pointed out that debris can litter space for decades after the break up of a rocket or satellite.

For instance in January 2007, China shot down one of its own satellites as part of an antisatellite test, said Jeffs. Debris from that could easily be problematic for the space station one day, even though the satellite was destroyed two years ago.

The piece of debris that forced the maneuvering of the shuttle and station yesterday was from a Chinese satellite that was launched in 1999 and broke up in 2000, NASA said.

"There's just more debris up there," said Jeffs, adding that the U.S. Strategic Command is constantly tracking it.