Crew boards space shuttle for launch from Florida

CAPE CANAVERAL, Fla, Sep 9 (Reuters) Six astronauts climbed aboard the space shuttle Atlantis today for a last-ditch attempt to launch a mission to resume construction of the International Space Station.

With weather conditions forecast to be favorable after a run of bad luck, liftoff is targeted for 2045 hrs from the Kennedy Space Center in Florida on the final day of the shuttle's two-week launch window.

NASA has been trying to get the shuttle and its six-member crew off the launch pad since Aug 27 Another delay would force NASA to wait until Russia completes a mission to the space station that is scheduled to begin next week.

Weather problems bedeviled the US space agency during its first week of launch attempts. A massive bolt of lightning struck the launch pad, prompting a two-day review to check the shuttle and ground equipment. Then the spacecraft was temporarily removed from the seaside pad because of threatening winds from a tropical storm.

This week's delays were caused by technical concerns: an unusual voltage spike in one of the shuttle's electricity generators and the unwelcome return yesterday of a mysterious fuel sensor problem that dogged NASA last year as it attempted to fly the first shuttle mission since the 2003 Columbia disaster.

The sensor is one of four that serve as a backup system to make sure the shuttle's engines shut down before the tank runs out of fuel.

Technicians filled the shuttle's 154-foot-tall fuel tank with a half-million gallons of cryogenic propellants early yesterday.

The crew, led by commander Brent Jett and including pilot Chris Ferguson, mission specialists Joe Tanner, Dan Burbank, Heidemarie Stefanyshyn-Piper and Canadian astronaut Steve MacLean, took their seats aboard the spacecraft for the second day in a row. yesterday's flight was called off less than an hour before launch.

With Atlantis' flight, NASA plans to restart construction of the International Space Station, which has been on hold since the Columbia accident. The crew is to deliver and install a 372 million dollars solar power module.

About half of the 100 billion dollars orbital outpost remains in pieces at the Kennedy Space Center awaiting rides on the shuttles.

NASA plans to stop flying the space shuttles by 2010 as the United States moves to a new spacecraft to fly crews to the space station and the moon.

The station components were all designed, however, to be launched only on the shuttle, putting pressure on NASA to operate its three-ship fleet consistently and safely so the station can be finished.

REUTERS PDM PM1903