Preparations start for fifth and Final Spacewalk

Astronauts of the shuttle Endeavour are preparing for the fifth and final spacewalk in this visit to the International Space Station. This spacewalk aims at mounting the shuttle's inspection boom on the space station's solar power truss for use by the next station assembly crew.

This was one of the busiest missions in the history of space shuttles with the maximum number of spacewalks ever performed during a joint shuttle-station flight.

During Saturday's spacewalk astronauts Robert Behnken and Mike Foreman will remove some thermal covers to check whether a micrometeorite hit showered debris throughout the joint. This joint has to continuously rotate 360 degrees to keep the solar wings always pointing toward the sun.

The spacewalk is scheduled to begin at 2123 GMT, after the station crew's sleep period.

The crew has already assembled a gigantic Canadian-built robotic maintenance man, whose assembly was completed in the third spacewalk.

The other purpose of Endeavour's crew was to drop off a storage compartment for the Japanese orbital lab named Kibo. The main part of the Kibo lab will be launched on the next shuttle mission in May.

The astronauts have set up Kibo's logistics module, transferring supplies and equipment into it from Endeavour's cargo bay.

"We had an absolutely fantastic day today," said lead shuttle Flight Director Mike Moses.

“The crew executed perfectly. They actually went faster than we thought,” he added.

The extension sensor-studded boom was also used to scan Endeavour's heat shield to ensure it is safe for next week's re-entry through the Earth's atmosphere.

Every shuttle crew that's flown since the Columbia disaster has used the boom to check for any problems with the shield. This shield protects the ship from the large amount of heat, which is produced when the shuttle enters the earth atmosphere and has the potential of damaging it.

NASA has made this scanning compulsory after the Columbia disaster in 2003.

The scanning is usually done after the spacecraft undocks from the station, but this time the boom had to be left at the station as the next shuttle mission, Discovery won’t have any space to carry the module and boom.

This is because the enormous Japanese Kibo lab will take up almost every square inch of the Discovery's cargo bay.

The shuttle Endeavour had left from the Kennedy Space Center in Florida on March 11 and is scheduled to land back on Earth on Wednesday evening at 2301 GMT.