science

The International Space Station's new starboard truss segment is seen above ... HOUSTON — Astronauts used a pair of robotic cranes to unpack the International Space Station's last set of solar wing panels from shuttle Discovery's cargo bay on Wednesday, part of three-day effort to bring the orbital outpost up to full power. Installing the power system is the primary purpose of NASA's 125th shuttle mission, which began Sunday with Discovery's blastoff from the Kennedy Space Center in Florida. The shuttle arrived at the station, orbiting 220 miles above Earth, on Tuesday for an eight-day stay. The shuttle and station crews used robot arms on both spacecraft to delicately maneuver the 31,000-pound (13,950 kg) girder, which contains the solar power panels, out of the shuttle and over to the space station. It is scheduled to be installed on Thursday during the mission's first spacewalk. Once in position, the station's 11-part spine will be complete after more than a decade of construction. NASA has up to nine shuttle missions remaining to finishing installing science laboratories and equipment to support an expanded, six-member space station crew. The power system, built by Boeing, is designed to supply 124 kilowatts of electricity to the station -- enough to power 42 average-sized U.S. homes. During their first in-flight interview, rookie astronauts said the rocket ride into space was smoother than they had expected. "The time kind of sneaks up on you. You're sitting there waiting and waiting and waiting and all of sudden you're inside the nine-minute hold (in the launch countdown) and you know you're going to go," said Richard Arnold, one of Discovery's two teacher-astronauts. "I was surprised at how relatively quiet it was -- a bit of shaking, a very smooth ride. I was expecting a bit more noise," he added. After reaching orbit, the crew surveyed their ship's heat shield for damage. NASA on Wednesday told the crew the shuttle was in good shape and no additional inspections were needed. The shuttle is due back at the Kennedy Space Center on March 28.