CAPE CANAVERAL, Fla. (AP) – Astronauts guided into place and bolted down a 2-ton addition to the international space station Tuesday, making the first of three difficult spacewalks during space shuttle Discovery’s stay at the orbiting lab.

U.S. astronaut Robert Curbeam, a veteran spacewalker, and the European Space Agency’s Christer Fuglesang, who is making his first spacewalk, stepped outside at 3:31 p.m. EST as the space station flew 220 miles over central Europe.

Discovery commander Mark Polansky, who flew on a 2001 shuttle mission during which Curbeam took three spacewalks, told him, “OK, buddy. Welcome back. It has been a long time.”

Curbeam and Fuglesang guided mission specialists Joan Higginbotham and Sunita “Suni” Williams as they used a robotic arm from inside the station to install the $11 million addition along the space lab’s truss in a space where clearance at times was less than 3 inches.

The settings on the robotic arm had to be adjusted in order to place the segments’ corners properly into alignment with the corners of the truss.

“We don’t want to scream over the loop,” said Higginbotham, referring to the communications system that links the spacewalkers, Mission Control and the space station, after a difficult maneuver. “But we’re very happy.”

The spacewalkers, who are tethered at all times, later planned to replace a camera outside the station and move a handle that was used to grip the new segment.

The spacewalk started several hours after NASA engineers studying Discovery’s heat shield for damage recommended against any extra inspection of the spacecraft’s belly and wings.

The engineers’ recommendation doesn’t mean the shuttle was cleared of damage, since experts were still reviewing data, but it was an optimistic sign. Later in the day, mission managers approved the recommendation.

The additional inspection had been considered for today to get a better look at dings spotted on the heat-resistant tiles on Discovery’s belly and the shuttle’s wings, where sensors detected “very low” readings on Sunday and Monday, possibly from shock waves and a micrometeoroid. Engineers also are interested in an orange cellophane-like material, used to keep nitrogen in place during launch, that was sticking out of the shuttle’s left external fuel tank door.

The engineers’ recommendation was welcome news for the crew and flight controllers who have been especially alert to damage to the shuttle’s heat shield since the Columbia tragedy in 2003. A piece of foam broke off Columbia’s external fuel tank during liftoff and gashed a wing, allowing hot gases to penetrate the spacecraft during its return to Earth. All seven astronauts died.

In post-Columbia missions, NASA has images taken during liftoff as well as meticulous camera inspections using the shuttle’s robotic arm attached to a boom. Discovery’s astronauts on Monday also took some impromptu photos of the wing using the shuttle’s robotic arm.

Another inspection of Discovery’s heat shield is planned next week after the shuttle undocks from the space station, and engineers plan to take that opportunity to study the area of the wing where they think the micrometeoroid struck.

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Associated Press Writer Rasha Madkour in Houston contributed to this report.

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On the Net:

NASA: http://www.spaceflight.nasa.gov/

AP-ES-12-12-06 1825EST