Spacewalk to Go Ahead as Space Junk Threat Fades

This story was updated at 3:20 p.m. EDT.

Two astronauts will float outside the International Space Station for a spacewalk Thursday evening secure in the knowledge that their spacecraft won?t have to dodge a massive piece of space junk.

Mission Control initially told the astronauts last night to try to begin Thursday?s spacewalk early so they could get back inside in time to move the space station clear of the approaching debris.

But further analysis found that the maneuver will be unnecessary since the space junk will pose no risk to the space station and shuttle when it zooms by Friday morning.

?It?s a relatively large, easy to track object,? said station flight director Royce Renfrew in a mission update. ?The probability of the two objects coming together in space is zero, so we stood down on that.?

The space junk is a massive piece of a European Ariane 5 rocket that launched two satellites into space in 2006. It will make its closest approach to the linked shuttle and station early Friday at about 10:06 a.m. EDT (1406 GMT).

The derelict rocket trash is about 204 square feet (19 square meters) in area and is flying in an extremely elliptical orbit that reaches nearly 20,000 miles (32,000 km) at its high point.

Spacewalk on tap

While NASA tracked the space junk overnight, shuttle astronauts Danny Olivas and Christer Fuglesang prepared for their Thursday evening spacewalk. Mission Control radioed the astronauts around mid-day to let them know the space debris was of no concern.

?Well that?s great news and we can focus on the [spacewalk] today,? Discovery commander Rick Sturckow replied.

The astronauts are scheduled to climb into their NASA-issue spacesuits and float outside the space station at about 5:19 p.m. EDT (2119 GMT) to install a massive new ammonia coolant tank during the 6 1/2-hour spacewalk.

The tank weighs just over 1,700 pounds (772 kg), and while it floats in weightlessness the astronauts will still have to take great care because of its hefty mass. Astronauts removed an old ammonia tank and stored it at the tip of the station?s robotic arm on Tuesday.

?Not only the robotic arm will have its hands full, I will also have my hands full,? Fuglesang said in a NASA interview. ?So it will be, I think, pretty spectacular ?. I think there can be some good photos.?

Thursday?s spacewalk will be the fourth career excursion for both Olivas and Fuglesang, who is a Swedish astronaut representing the European Space Agency.

It will be the second of three spacewalks planned for Discovery?s 13-day mission to deliver new supplies, science equipment and a treadmill named after comedian Stephen Colbert.

• New Video - STS-128 Spacewalk Overview
• Video - The Expanding Danger of Space Debris
• Video - Stephen Colbert to NASA: 'No Chubby Astronauts'

SPACE.com is providing complete coverage of Discovery's STS-128 mission to the International Space Station with Managing Editor Tariq Malik and Staff Writer Clara Moskowitz in New York. Click here for shuttle mission updates and a link to NASA TV.