The installation marked the resumption of the half-finished orbiting laboratory's construction, which was halted after the 2003 Columbia tragedy that left seven astronauts dead.

Astronauts used the station's robotic arm to place the 16-tonne truss segment with two solar arrays that had been brought aboard the shuttle's payload bay. Tanner and Stefanyshyn-Piper then stepped out of the station to connect the cables in the first of three planned spacewalks.

NASA officials deemed the duo's excursion a success, although a bolt was lost in space during the task. Officials at the Johnson Space Center in Houston, Texas expressed confidence that the piece would pose no danger to the station or shuttle.

"Joe and Heidi, you did a phenomenal job and set the bar very high for the rest of the assembly," Mission Control in Houston said after the spacewalk.

The astronauts moved through their tasks so quickly that flight controllers gave them the greenlight to take on work scheduled for future spacewalks.

"It was an outstanding day," lead shuttle flight director John McCullough told reporters. "All was accomplished successfully and flawlessly."

Canadian Space Agency astronaut Steve MacLean and American counterpart Dan Burbank quickly began preparations for the second spacewalk scheduled for 1015 GMT Wednesday.

The solar arrays will measure 73 meters (240 feet) long once they are unfurled Thursday and will eventually double the station's power capabilities.

The 11-day Atlantis mission has been billed as the most complex station assembly work to date.

The last ISS assembly work was in November 2002, as the Columbia disaster in February 2003 forced the National Aeronautics and Space Administration to focus on improving shuttle flight safety.

Following two Discovery shuttle missions aimed at making space flight safer, NASA said it was ready to resume space station construction.

On its way to the ISS, Atlantis' heat shield had a thorough examination in what has become a routine safety check since the Columbia accident.

Before docking, Commander Brent Jett steered the orbiter into a backflip 200 meters (yards) below the ISS to allow the station crew to photograph Atlantis' underbelly.

On Sunday, the Atlantis astronauts used the orbiter boom sensor system, attached to the end of the robotic arm, to closely inspect the wing leading edges and the nose cap for potential damage from debris during the launch.

A NASA spokeswoman said late Monday that the space agency decided that a "focused" inspection was unnecessary. Such an inspection would have added another day to the mission's already packed schedule. The decision indicates that officials found none of the damage from debris that could have hit its heat shield during liftoff from the Kennedy Space Center in Cape Canaveral, Florida. Columbia was doomed by foam insulation that peeled off its external fuel tank during liftoff and pierced its heat shield, causing it to disintegrate as it returned to Earth in February 2003.

NASA plans 15 more shuttle trips to complete the ISS by 2010, when the three-shuttle fleet is to be retired.

Completing the ISS is central to US ambitions to fly humans back to the Moon and eventually to Mars.

Related Links
NASA ISS
Space Station News at Space-Travel.Com

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