HOUSTON -- Two spacewalking astronauts unhooked a 35,000-pound girder from the international space station Sunday, starting the delicate process of moving the giant solar power tower to another part of the orbiting outpost.
Spacewalkers Scott Parazynski and Daniel Tani started their 61/2-hour jaunt by disconnecting cables and unscrewing bolts that connected the girder to the space station's backbone.
They then guided astronauts Stephanie Wilson and Douglas Wheelock as they used the station's robotic arm to detach the huge truss.
"Don't drop it!" joked one of the spacewalkers.
The robotic arm operators inside the station will move the girder to a location where it can be temporarily parked. Installation is set for Tuesday during the mission's third spacewalk.
Parazynski and Tani later added equipment to the outside of Harmony, a school bus-sized chamber that was delivered by Discovery and installed during the mission's first spacewalk. The crew entered the room for the first time on Saturday.
Besides spacewalking handrails, the astronauts attached a fixture on Harmony that will allow the station's robotic arm to move the compartment from its current temporary location to its permanent home.
The space station's crew will relocate Harmony after Discovery leaves in another week.
The European Space Agency's science laboratory, named Columbus, will hook onto Harmony as early as December. The Japanese Space Agency's lab -- called Kibo or in English, Hope -- will latch onto Harmony early next year.
Harmony also will function as a nerve center, providing air, electricity and water for the space station.
While Parazynski worked on Harmony, Tani checked for sharp edges on railroad-like tracks for the space station's robot arm. He found dozens of micrometeorite dings on a handrail along the tracks, but nothing particularly sharp that might have cut spacewalkers' gloves on two recent flights.
Tani also inspected a rotary joint for the station's solar wings that has been exhibiting vibrations and electrical current spikes for the past 11/2 months. Metal shavings were everywhere, clinging to the joint as if to a magnet. Tani used tape to collect some for analysis back on Earth.
"Great discovery, Dan," Parazynski said, adding that he didn't think Tani would be able to see anything inside the joint.
"It's quite clear that it's metal-to-metal grating or something, and it's widespread," Tani replied. "Wow," Parazynski said.
While they worked, Tani caught a glimpse of Ireland through the clouds and had a chance to wave at his friends and family there. Tani met his Irish wife while golfing in Cork. And later, as he wrapped up the spacewalk, he got to see Chicago and even nearby Lombard, his hometown, 210 miles below.
"Can't wait to get back there and share all my stories with them," he said.
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