Shuttle to check heat shield, deploy satellites

LOS ANGELES, Dec 20 (Reuters) Astronauts aboard Discovery plan a final, routine check of the space shuttle's heat shield and the launch of two small satellites today before before landing two days later.

The crew will use cameras on the shuttle's robotic arm to scan Discovery's leading edges, wings and nose cone for damage from micrometeroid strikes during the eight days it was docked with the International Space Station.

The shuttle slipped away from the space station at 5:10 pm EST 0340 hrs IST yesterday after its crew helped rewire the orbiting outpost, dropped off rookie astronaut Sunita Williams and picked up Thomas Reiter, a German astronaut who spent nearly six months on the station.

Discovery's crew also delivered equipment, food and supplies, installed a new segment to the station's metal backbone and delivered shields to better protect the station's living quarters against micrometeoroid strikes.

''We wish you smooth sailing and thanks for the hospitality and hard work,'' Discovery commander Mark Polansky told the space station crew as he fired the shuttle's steering thrusters to leave the station's orbit.

NASA has been meticulous about inspecting the shuttle fleet after launch and before landing after the shuttle Columbia broke apart as it re-entered Earth's atmosphere in 2003 because of damage to its heat shield.

Astronauts and ground controllers inspected the heat shield after Discovery's December 9 launch and found no damage from its journey into orbit.

Another inspection expected to last about five-and-a-half hours is today's priority, along with checking the flight control systems and stowing gear for landing.

After the inspection, the crew is scheduled to remotely launch two technology demonstration satellites from the shuttle's payload bay.

The coffee-cup sized MEPSI, or Microelectromechanical System-Based PICOSAT Inspector, will test how well small autonomous satellites can observe larger spacecraft.

The Radar Fence Transponder, or RAFT, built by US Naval Academy students, uses two small satellites to test the limits of the Space Surveillance Radar Fence, a radar system that detects orbital objects passing over the United States.

Tony Ceccacci, lead flight director for the shuttle, said the satellite deployments could be sacrificed if the heat shield inspection runs long.

The shuttle crew has a narrower-than-usual landing window because managers decided to extend their stay at the space station by a day to finish repairs on a stuck solar panel.

NASA must use one of two days' emergency supplies reserved for landing delays to perform the heat shield inspection. But the agency has mobilised backup landing sites in California and New Mexico to get the spacecraft down before its fuel supplies run out on Saturday.

A NASA spokesman said late yesterday that Discovery was still scheduled for a Friday afternoon landing at Kennedy Space Center in Florida, although mission controllers were watching forecasts for a 40 per cent chance of rain and thunderstorms.

NASA is under a firm deadline to finish the 100 billion dollars space station by the shuttle's 2010 retirement date. At least 13 more missions are needed to finish construction.

REUTERS PB DS1200