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NASA delays Discovery landing until Tuesday
During the trip, a pair of spacewalking astronauts replaced a failed 660-pound gyroscope, which controls the orientation of the station, and restored power to another. Sunday was the first time in three years that all four of the station's gyroscopes ran simultaneously.
In a third unprecedented spacewalk, astronaut Stephen Robinson went beneath Discovery's belly to gently tug out two protruding thermal tile fillers. Engineers on the ground worried the material could cause dangerous overheating during re-entry and could lead to another Columbia-type catastrophe. Those on the ground learned about the material jutting out from Discovery's fragile thermal tile belly through intense inspections of the ship using cameras and lasers. As a result of Columbia, Discovery's crew inspected their ship for damage on five different days during the mission and also tested repair techniques developed since the tragedy. Columbia was doomed by a 1.67-pound piece of foam that broke free from an external fuel tank at launch. The foam pierced a hole in the ship's left wing and as the spacecraft re-entered the Earth's atmosphere, searing gases melted the wing from the inside, causing the ship to break apart. All seven astronauts aboard were killed. NASA officials' excitement over Discovery's return to space was dampened by video that showed a nearly 1-pound chunk of foam �� reminiscent of the one that doomed Columbia �� breaking free from Discovery's external tank shortly after liftoff. The foam did not strike Discovery. The agency quickly grounded future flights, saying that more work must be done, despite spending hundreds of millions of dollars to redesign the tank. Despite the setback, NASA says Discovery's flight has taught important lessons and overall been an "incredible" success. "We've shown that we've been able to return the vehicle back to safe operational flight," astronaut Andrew Thomas said Sunday aboard Discovery. "There's a lot of success that goes with this mission that I think is going to be important for the long-term future and well-being of this flight program."
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