Countdown restarts for space shuttle launch

CAPE CANAVERAL, Fla., Sept 3 (Reuters) - NASA restarted its countdown clocks today at the Kennedy Space Center for the launch this week of the US space shuttle Atlantis after a week's postponement due to a lightning strike and a storm.

Liftoff of the shuttle and its six-member crew is targeted for 12:29 p m EDT (1629 GMT) on Wednesday. The flight will be NASA's first mission to restart construction of the International Space Station since the 2003 Columbia disaster.

Liftoff was postponed from last week due to Tropical Storm Ernesto and a lightning strike on the shuttle's seaside launch pad in Florida.

The US space agency now has three days -- Wednesday, Thursday and Friday -- before its launch window closes and it would have to delay until late October.

Atlantis will kick off a final spate of space station assembly missions that must be finished by 2010, when the shuttle fleet is to be retired. The shuttles are the only vehicles designed to carry the station's major components to orbit.

The 0 billion international orbital outpost was about half finished when NASA lost the space shuttle Columbia and its seven astronauts on February 1, 2003. The spacecraft broke apart as it headed toward landing because its heat shield had been damaged by falling foam insulation during liftoff.

NASA spent three years redesigning the shuttles' external fuel tanks, from which the foam fell off, and implementing other safety upgrades before flying two test flights, one last year and the second this July.

REUTERS AB KP2245