Astronauts end heat shield scan, deploy satellites

CAPE CANAVERAL, Fla., Dec 21 (Reuters) The shuttle Discovery astronauts completed an inspection of their ship's heat shield yesterday and remotely deployed two small satellites ahead of tomorrow's scheduled landing.

The inspection was intended to find any damage from tiny meteoroids or space debris that may have occurred since the shuttle reached orbit on December 9. The astronauts inspected their ship once already to see if it made it through the launch without problems.

Yesterday, the shuttle and ground crews wrapped up the nearly six-hour scan of Discovery's wings and nose, then powered down and stowed the robotic arm that ran a camera and boom equipped with laser sensors over the ship's heat shield.

''Hopefully there is nothing to see,'' Discovery Commander Mark Polansky said of images and data transmitted to a ground crew that will analyze it overnight before clearing the shuttle for landing.

The Discovery astronauts also deployed two small technology demonstration satellites from the shuttle's payload bay.

Both inspections stem from safety upgrades implemented after the 2003 Columbia disaster, which was triggered by a piece of foam insulation that fell off the shuttle's fuel tank during launch and hit the ship's wing.

The shuttle broke apart as it flew through the atmosphere for landing 16 days later, killing all seven crew members.

Though Discovery showed no signs of damage from launch, NASA decided the final inspection was more important than preserving the standard two-day supply of cryogenic chemicals, which are used to make electricity, for any weather-related or technical problems that might postpone landing.

HOMECOMING Discovery's mission had been slated to last 12 days but was extended a day to retract a jammed solar wing panel on the International Space Station.

Discovery departed the space station on Tuesday after rewiring the orbiting outpost and adding a truss segment to its backbone.

With just one day's supply of liquid oxygen and liquid hydrogen in the tanks, Discovery is poised to return to Earth on Friday. NASA mobilised all three shuttle landing sites, including its rarely used New Mexico landing strip, to improve the chances of a homecoming tomorrow.

Meteorologists were predicting possible rain and clouds at the prime landing site in Florida and potentially high winds at the backup landing site in California. The White Sands Space Harbor in New Mexico, however, was expected to be clear.

NASA has only landed a shuttle in New Mexico once, in March 1982 when Columbia returned from its third spaceflight. The shuttle was damaged by sand.

Mission controllers said on Wednesday that cargo planes carrying essential runway equipment, including a purge unit to keep the shuttle's systems at the proper temperatures, had been sent to New Mexico in case Discovery lands there.

The Discovery astronauts will have two opportunities to land at the Kennedy Space Centre in Florida tomorrow, at 3:56 pm (local time) and 5:32 pm. The first landing opportunity in either California or New Mexico would occur at 5:27 pm.

Discovery's flight is the fourth since the Columbia accident. NASA plans to fly at least 13 more missions to complete construction of the half-built, 100 billion dollars space station.

REUTERS PKS RN0753