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Space Shuttle Undocks from ISS

The U.S. space shuttle Discovery has departed from the International Space Station (ISS), but has not gone far away. It will remain in the vicinity of the outpost until flight controllers are certain there is no surface damage that would endanger Monday's planned landing.

After a week-and-a-half visit, the shuttle and station crews bid each other farewell and closed their hatches. Discovery pulled away slowly and almost immediately, its crew began scanning parts of its heat shielding that protects it from the fiery re-entry through the atmosphere. They scanned the nose cone and front edge of its right wing with the robot arm camera for any potential damage from tiny space rocks called micrometeoroids.

They had scanned the edge of the left wing on Friday and earlier in the mission, checked the condition of the shuttle's fragile ceramic tiles.

The U.S. space agency NASA has added this task to avoid another shuttle catastrophe like Columbia in 2003. Launch debris punctured a hole in its wing, leading to its disintegration upon re-entry into the atmosphere. If Discovery's wing is seriously damaged by space rocks, the crew can seek safe haven on the space station until another shuttle comes to rescue them.

As a result, the shuttle is remaining just 70 kilometers from the station until mission managers are sure that Discovery's surface is free of cracks or holes. If so, they will give their final permission for a landing.

Flight director Tony Ceccacci says the surface inspections have taken up a lot of time on this mission. He says space agency officials will analyze results to determine if the effort is worth doing again.

"For our flight, we were able to accommodate it, but we're looking at future to see, does it require taking some of the mandatory activities of that flight off the plate to accommodate it? So we're going to evaluate and see if the data we get from it and the crew time that's required to do it is justifies doing it in future flights," he said.

Mission controllers continue to monitor a slow leak of some substance from one of three units that supply power to landing gear hydraulic systems during shuttle re-entry and touchdown. Deputy shuttle manager John Shannon says flight controllers are being cautious and assuming the drip is fuel, but he says the drip is so slow that it poses no threat of fire inside the shuttle.

"We're okay where we are right now. We're okay if it stays the way it is right now. If it doesn't change, we'll probably use it as we normally would for entry," he said.

But if the leak rate increases, Shannon says flight controllers will activate the power unit before re-entry to use up the fuel to avoid any possible trouble. He says two hydraulic power units are enough for a safe landing.