CAPE CANAVERAL, Florida - Nasa managers have cleared space shuttle Discovery for a launch attempt on Thursday (Fri NZT), though the weather outlook was not favourable.
Two technical issues, one with the shuttle's electrical system and the other concerning an adhesive used in the ship's solid rocket boosters,were resolved, Nasa said, leaving the shuttle in good health for liftoff at 9:36pm EST (3.36pm Fri NZT).
The primary goal of the flight, which is the 117th in shuttle programme history, is to rewire the International Space Station's electrical and cooling systems.
It is a daunting task that will require intricate and well-timed co-ordination between the shuttle and station crews, spacewalkers working outside the station and ground control teams in Houston.
The first trial, however, will be getting off the ground. A cold front expected to pass over central Florida on Thursday may force Nasa to postpone the launch.
Meteorologists downgraded the chance of launching on Thursday night to just 40 per cent due to expected low clouds.
Weather at Nasa's three overseas emergency landing sites also is unfavourable, said Air Force meteorologist Kathy Winters.
The outlook for Friday was even worse, with only a 30 per cent chance conditions will be suitable for liftoff.
"Unfortunately, the weather continues to deteriorate because of the winds," Winters said at a briefing.
Winds on Friday night are expected to peak at about 56km/h, exceeding Nasa's limit by more than 50 per cent.
Saturday's forecast perks up a bit, but remains dim with only a 40 per cent chance that the shuttle will be able to fly.
In addition to rewiring the space station, Discovery's crew will deliver an external truss segment, supplies and a new resident crew member. The flight will be Nasa's third and final shuttle mission this year.
