SPACE CENTER, Houston -- Endeavour's astronauts overcame their first hurdle Saturday in building the international space station: hoisting the 25,000-pound Unity chamber from the shuttle cargo bay with only an inch of clearance on either side.

An even tougher job awaits them Sunday, when they attempt to pluck a much larger Russian station component from orbit and attach it to Unity without a direct line of sight.The six shuttle astronauts have been chasing the component named Zarya (Russian for Sunrise) since they rocketed into orbit Friday. They trailed the giant cylinder by 6,000 miles Saturday evening.

Astronaut Nancy Currie used Endeavour's 50-foot robot arm to lift Unity, the first American-made piece of the international space station. She moved the precious load slowly -- so slowly it almost appeared at first to be motionless.

"Beautiful and delicate work," radioed Mission Control.

Currie raised Unity about 13 feet before tilting it to an upright position above a docking ring in the cargo bay. She lowered the cylinder to within a few inches of the ring; then the pilots fired Endeavour's thrusters and the shuttle moved up just enough for the pieces to snap together. The entire process took two hours.

The last thing she wanted to do was bump Unity against the shuttle while lifting it from its horizontal position and setting it upright in preparation for Sunday's coupling with Zarya.

The jointed shuttle arm, which also will be used for handling the 41-foot, 44,000-pound Zarya, has never wielded such massive objects before. The two station components are so big that Currie won't be able to see where they meet by looking out the window.

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