NASA weighs repair to Damaged shuttle, extends mission by three days*

WASHINGTON (AFP) - - NASA specialists on Sunday began analyzing a gash
in the shuttle Endeavour's heat shield to decide if it needs repair, and
said it was adding three days to the mission to continue work on the
International Space Station.

The prolongation of the mission means that the Endeavour, launched
Wednesday from Cape Canaveral, Florida, will now return to Earth on
August 22, a National Aeronautics and Space Administration spokesman said.

The extra time will allow a fourth, additional spacewalk to the mission
to continue construction work on the orbiting laboratory. On Saturday
the station was expanded with a new truss segment attached by two
astronauts.

Endeavour's tour was initially planned for 11 days, with three space
walks. NASA however said from the start said it would extend the mission
after testing a new system that transfers electricity from the ISS to
the shuttle.

The system, which prolongs the life of the shuttle's batteries and
allows it to remain aloft longer, was tested successfully on Sunday,
NASA said.

Meanwhile NASA engineers at mission control in Houston, Texas, were
poring over three-dimensional images of a gouge in the shuttle's heat
shield. The images were taken Sunday by a camera, and measurements by a
laser, both of which trained on the shuttle's underbelly.

The examination took about three hours as the imaging devices atop a
30-meter-long (100 foot) robotic arm coupled with the Orbiter Boom
Sensory System (OBSS) scanned five areas on the shuttle underside that
may have been damaged during Wednesday's launch from Cape Canaveral,
Florida, NASA said.

The gouge, 30.5 x 25.5 millimeters (1.2 x 1.0 inches) -- smaller than
initially reported -- and 28.5 millimeters (1.12 inches) deep, was made
near a landing gear hatch by a piece of foam, possibly covered with ice,
that broke off the shuttle's external fuel tank shortly after blastoff.

Mission Management Team chairman John Shannon said an exact mold of the
gash will be reproduced in thermal tiles and tested in a laboratory that
simulates the extreme heat and friction the shuttle encounters on
reentry to Earth.

NASA engineers will be able to "do a thermo analysis model ... to
understand what the actual heating impact of reentry will be for a
damage of this type," he told a press conference.

The tests, to be carried out "in the next 24 to 48 hours," should
provide engineers enough data to determine whether repairs are needed to
the damaged heat shield before the shuttle undocks from the ISS on
August 20, he said.

"If it comes back that a repair is desirable to do," he added, "we have
three different methods of doing that."

Without explaining what the repairs entail, Shannon said he had "a lot
of confidence if a repair is required that they will be executed."

The foam came off the shuttle's fuel tank, which holds super-cold liquid
hydrogen fuel for the takeoff and is jettisoned before orbit is reached.
An insulation layer on the tanks is supposed to prevent icing.

The US space agency keeps a watchful eye on the thermal tiles that cover
the shuttle since the Columbia disaster of February 2003.

Columbia's protective heat shield was pierced by a piece of insulating
foam that peeled off its external fuel tank during liftoff. The breach
resulted in the shuttle disintegrating as it re-entered Earth's
atmosphere, killing all seven astronauts on board.

After the examination of the shuttle's underside was completed at 1900
GMT, preparations began for the mission's second spacewalk, due to start
at 1531 GMT Monday, during which astronauts Dave Williams and Rick
Mastracchio will replace a faulty ISS control gyroscope.

On Saturday, Mastracchio, of the United States and Canadian Dave
Williams spent six hours and 17 minutes installing and activating a new,
1.58-ton segment for the ISS that the Endeavour had delivered.

Endeavour docked on Friday with the ISS bringing seven astronauts,
including 55-year-old Morgan, the first school teacher in space.