US space shuttle cleared for return

HOUSTON, July 17: With the last potential snags to landing cleared, the astronauts on space shuttle Discovery hoped for good weather to cap a comeback mission for NASA with a Florida touchdown.

The shuttle was scheduled to land today at 9:14 a.m. EDT (1844 IST) at Kennedy Space Center if the weather cooperates.

Mission Control communicator Steve Frick radioed that final inspection of the heat shield showed Discovery's wings and nose ''all looked good.'' He also said ''we're feeling ... more comfortable'' that a hydraulic power unit leak isn't a problem.

''You are cleared for entry,'' Frick radioed Discovery from Johnson Space Center in Houston.

''That sounds great,'' shuttle commander Steve Lindsey responded.

Florida's summer weather appeared to be the last hurdle. There is a chance of showers, and flight rules bar a landing attempt if there is rain within 35 miles of the Kennedy runway.

''It's always a challenge ... (but) I think we have a pretty good shot at getting into Kennedy tomorrow,'' said entry flight director Steve Stich.

There are two opportunities to land in Florida today, about 90 minutes apart. If the shuttle can't land as planned, NASA would wait until tomorrow, and add Edwards Air Force Base in California and White Sands, New Mexico, as backup sites.

Discovery has only enough oxygen to stay in space until Wednesday, NASA said.

The landing will be the first to test two improvements -- bigger, stronger tires and a new navigation system that will rely on global positioning satellites.

NO DAMAGE TO HEAT SHIELD To get ready, the crew powered up flight control systems, and all passed the test, NASA engineers said. Final heat shield scans were conducted with cameras and sensors, and analysts found no damage.

This 13-day mission was critical to a US space agency still recovering from the 2003 disaster in which shuttle Columbia broke apart -- killing seven astronauts -- as it returned to Earth after falling fuel tank foam cracked its wing heat shield during launch.

After spending 1.3 billion dollar and 3-1/2 years on repairs and safety upgrades, NASA needed to prove it could safely fly the shuttle again.

Flecks of fuel tank insulation foam flew off during Discovery's takeoff, but NASA said they were too small and too late in the launch to be dangerous.

''I personally believe that we are back on track,'' Lindsey said during a round of television interviews from space on Sunday.

Discovery, making only the second shuttle flight since the Columbia accident, docked with the International Space Station for nine days, during which astronauts Piers Sellers and Michael Fossum performed three space walks.

They repaired a broken transporter that will be needed to complete construction of the half-finished 100 billion dollar space station complex and tested shuttle repair techniques.

Discovery launched with seven astronauts on board, but left one -- Germany's Thomas Reiter -- at the space station, giving the station three crew for the first time since 2003.

NASA plans to fly 16 shuttle missions by the end of 2010 to finish the station, which is sponsored by 16 nations. The next flight is scheduled to take off around August 28.

As the crew neared the end of perhaps the busiest shuttle mission, a TV interviewer asked for perspective on the Earth and the current Middle East conflict from 220 miles up.

''This is humanity's home,'' Sellers said. ''Hopefully one day we'll all get along.''

REUTERS