Deep cut found in Endeavour's heat-shield

Houston, Aug 14: Spacewalking astronauts manhandled a 600-pound (272-kg) gyroscope into place on the International Space Station while NASA managers assessed a small but deep pit in shuttle Endeavour's heat shield.

In the second of four spacewalks planned during the shuttle mission, astronauts Rick Mastracchio and Dave Williams replaced one of the space station's four gyroscopes yesterday, which spin like tops to keep the outpost properly positioned in orbit without the use of gas-burning rocket thrusters.

During the spacewalk, mission managers discussed what to do if anything about a deep cut in two of Endeavour's heat-resistant belly tiles discovered shortly before the shuttle parked at the station on Friday.

Endeavour's astronauts used a laser scanner and imager attached to an extension on the shuttle's robot arm on Sunday to make three-dimensional pictures of the gouge, which was caused by a piece of insulating foam that broke off the shuttle's fuel tank during launch last Wednesday and slammed into the underside of the orbiter.

NASA has made several tank modifications since the fatal 2003 Columbia accident, which was traced to a similar but far more serious impact with falling tank insulation. But changes to the part of the tank that shed foam during Endeavour's launch have not yet been implemented.

NASA has three more flights planned with its current tank design before the modification is ready.

In addition to deciding if Endeavour's tile damage is serious enough to warrant potentially risky repairs, NASA faces a larger question of whether additional modifications to the tank must be made before future shuttle missions are cleared for launch.

The agency is pressing to complete 11 more construction missions to the space station, two resupply flights and a final servicing call to the Hubble Space Telescope before the shuttles are retired in three years.

Gyroscopes, like the one replaced by the Endeavour crew yesterday, are among the items that so far have no rides to the station after the shuttle's retirement. As soon as the new device was bolted in, ground controllers tested electrical connections and pronounced the new equipment in good health.

''Alllllright! That's great news,'' shouted Endeavour astronaut Tracy Caldwell who was overseeing the spacewalk from aboard the station.

Mastracchio and Williams headed back inside the station's airlock at about 6 p.m. EDT (0330 IST), completing a 6 1/2-hour spacewalk. The next outing is scheduled for tomorrow.

Endeavour is due back at the Kennedy Space Centre in Florida on August 22.

Reuters>