The remains of a European rocket passed within 1.3 kilometers of the Space Shuttle Discovery and international space station Sept. 4 but did not come close enough to pose a risk to the spacecraft or their astronaut crews.

The space junk, part of an Ariane 5 rocket that launched two satellites into orbit in 2006, flew harmlessly past the linked station-shuttle complex at about 11:06 a.m. EDT as the 13 astronauts inside prepared for a day off.

NASA watched the approaching space junk for days to make sure it would not hit the space station or shuttle, or force the spacecraft to fire thrusters for an evasive maneuver. By early Sept. 3, the chances of the debris coming too close for comfort were nil, the space agency said. “We determined the chance of collision was zero,” NASA spokesman Bill Jeffs said.

The spent rocket hardware is relatively large by space debris standards –- about 19 square meters — and is flying in an extremely elliptical orbit that reaches nearly 32,000 kilometers at its high point.

Late Sept. 2, NASA considered several options to move the docked shuttle and space station to put more distance between them and the approaching space junk. At one point, the agency considered starting a scheduled Sept. 3 spacewalk early or delaying it a day in order to perform the move.

But it later became clear that the space debris posed no risk to the station and shuttle. The spacewalk went on as planned, with astronauts replacing a massive ammonia coolant tank for the space station’s cooling system.

It was the second of three spacewalks planned for Discovery’s 13-day mission, which is delivering nearly 8 tons of supplies, science equipment and a treadmill named after comedian Stephen Colbert to the space station.

Discovery is due to land back at Kennedy Space Center, Fla., on Sept. 10.