Astronauts to examine heat shield

CAPE CANAVERAL, Fla., July 5: Astronauts aboard the space shuttle Discovery will examine their ship's heat shield today for signs of damage as they head toward a rendezvous with the International Space Station on a critical mission for the US shuttle program.

Discovery was launched successfully from Florida on Tuesday on just the second mission since the destruction of shuttle Columbia in 2003. Another accident or serious problem could ground the shuttle fleet permanently.

NASA officials said the shuttle's troublesome external fuel tank, which triggered the Columbia accident, shed some small pieces of insulating foam during Discovery's launch. But the losses were expected and were no immediate cause for concern.

''At the end of the day, I'm very pleased with the performance of the tank,'' shuttle program manager Wayne Hale said. ''This is a great improvement over where we were.'' NASA managers had warned for weeks that the shuttle's fuel tank would continue to shed debris, but had said no pieces would be large enough to damage the shuttle in case of impact.

Columbia was destroyed when a 1.67-pound (756-gram) chunk of foam broke off from its fuel tank and smashed into the ship's left wing. The damage was undetected until after Columbia broke apart 16 days later as it flew back into the atmosphere from space, killing all seven astronauts aboard.

NASA spent 1.3 billion dollars over the last three years to fix the fuel tank and make safety upgrades to the shuttle. The agency needs a successful mission to resume construction of the half-built, 0 billion space station, which has been on hold since the Columbia accident.

The astronauts will use a sensor-laden boom to scan Discovery's wings and nose-cap, areas particularly vulnerable to damage. The crew will photograph and videotape the heat-resistant tiles on the shuttle's belly as Discovery approaches the space station for docking on Thursday.

''We can detect very small damage indeed, down to about an eighth of an inch, I believe,'' Hale said.

Discovery's 12-day mission is meant to test the fuel tank repairs and deliver badly needed supplies and equipment to the space station. The astronauts will make two spacewalks.

One will test a new 50-foot (15-metre) extension to the shuttle's robot arm. Crews use the boom to inspect the ship for damage but NASA wants to know if it could be used to maneuver spacewalkers to inaccessible parts of the shuttle for repairs.

During the second spacewalk, astronauts Piers Sellers, a British-born climate scientist, and Michael Fossum, an American making his first spaceflight, will try to fix the space station's broken mobile transporter.

The transporter, a cart that travels on tracks on the outside of the space station, will be needed to install trusses and solar arrays on the space station. It has been broken since December.

Plans are in place for a third spacewalk if the shuttle has enough fuel to extend the mission for a day.

REUTERS