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Debris that worried scientists no longer threat to space station

By the CNN Wire Staff
  • NEW: Threat of space debris coming too near the International Space Station has passed
  • Three Americans and three Russians are on board the space station
  • A NASA expert says "non-trackable debris" is the greatest threat to space missions
  • A piece of space debris was projected to pass close by the space station

(CNN) -- The debris that scientists were concerned about earlier Thursday is now not expected to come too near the International Space Station, NASA said.

The debris will come no closer than 8 kilometers (5 miles) to the space station, NASA said. No crew action is required and operations will not be affected. Mission Control gave the Expedition 24 crew the all-clear at 12:45 p.m. ET.

Earlier Thursday, NASA said the piece of debris from a Chinese satellite might pass close enough to the space station to require astronauts to take shelter in their Soyuz aircraft. The closest pass was expected around 1:47 p.m. ET.

NASA said the object has proven difficult to track precisely.

Mission control centers in the U.S. and Russia were keeping a close eye on the debris, NASA said.

Six people -- three Americans and three Russians -- are on the International Space Station, NASA said. The Americans are Tracy Caldwell Dyson, Shannon Walker and Douglas H. Wheelock; the Russians are Skvortsov Alexander Alexandrovich, Kornienko Mikhail Borisovich and Fyodor Nikolayevich Yurchikhin.

Space debris, which can travel at speeds exceeding 17,000 mph, constantly threatens satellites and spacecraft, according to NASA's website.

"The greatest risk to space missions comes from non-trackable debris," said Nicholas Johnson, NASA chief scientist for orbital debris.

According to NASA's website, more than 500,000 pieces of "space junk" are tracked as they orbit the Earth. Although most of the orbital debris is relatively small, some 20,000 pieces are larger than a softball, which NASA keeps track of because scientists say it poses a serious threat, especially to the International Space Station.

NASA has created a long-standing set of guidelines -- known as flight rules -- on how to deal with each potential collision threat.

These flight rules are used to assess whether the threat of a close-approaching orbital piece of debris is sufficient to warrant evasive action or precautions to ensure the safety of space crews or space equipment, according to NASA's website.