CAPE CANAVERAL, Florida - Nasa workers at the Kennedy Space Centre in Florida today began a risky repair job to replace faulty bolts on the US space shuttle Atlantis a week before its scheduled launch.
Technicians set up work platforms to reach into the forward portion of the shuttle's 18-metre-longpayload bay as Atlantis stood upright on its launchpad.
Atlantis is due to blast into orbit on August 27 on the first shuttle mission aimed at resuming construction of the US$100 billion ($158.62 billion) International Space Station since the 2003 Columbia disaster. Two shuttle missions carried out since the Columbia accident have tested safety upgrades.
Nasa decided to swap two of the four bolts holding Atlantis' main communications antenna in place because they were found to be dangerously short, and liable to pop out during liftoff with potentially catastrophic results.
The mistake was made 25 years ago when Atlantis was built and the spacecraft has safely flown 26 times.
The repair itself is tricky.
A sole technician, lying on his or her side on a narrow gangplank attached to a work platform, will replace the suspect bolts. Access is difficult because of the shuttle's vertical position.
Shuttles Endeavour and Discovery also were found to have faulty bolts, but since they were in horizontal positions in processing hangars, the repair work on them was relatively simple.
Nasa expects the work on Atlantis to finish on Sunday. The space agency says the repairs should not delay Atlantis' August 27 launch.
"The bolt change-out work itself is probably going to be very straightforward, assuming we don't get into any 'gotchas,"' said Nasa launch director Mike Leinbach.
Atlantis and its six crew are due to carry a 16 tonne truss segment that contains the space station's second set of solar arrays. The power upgrade is expected to double the amount of electricity available for the station.
Construction of the orbital outpost, a multinational effort, began in 1998.
The shuttles are the only spacecraft capable of carrying its larger components and assembly must be completed by the time the US shuttle fleet is retired in 2010.
