Washington - Astronauts Robert Behnken and Mike Foreman began the Endeavour's fifth and final spacewalk Saturday to stow a boom outside the space station that the shuttle will leave behind when it returns to Earth next week. The 17-metre-long boom was designed as a safety backstop to help the ageing shuttles perform post-launch self examinations for tile damage. Tears in the outer thermal skin that occurred on liftoff were blamed for the 2003 Colombia disaster that killed its seven astronauts as they tried to return to Earth.
Because of the size of the next piece of Japan's Kibo laboratory to be transported to the space station on Discovery shuttle in May, there won't be room enough in the cargo bay for the Orbiter Boom Sensor System (OBSS,) as it is called, NASA officials explained.
So OBSS will be stored outside the space station until Discovery arrives in May. During the seven-hour spacewalk, Behnken and Foreman are fastening a "keep alive" cable from the space station to the boom to provide it with heat and power to keep its sensitive instrumentation"safe" while it is stored "in the harsh space environment," NASA said.
Behnken and Foreman are being aided by two robot arms. The shuttle's own robot fetched the OBSS out of Endeavour's cargo bay and handed it over to the space station's Canadian-designed robot arm called Dextre.
The spacewalkers also intend to install covers on the first part of Japan's Kibo, which was joined to the space station on an earlier spacewalk, and inspect a solar panel joint.
The spacewalk began nearly an hour ahead of the scheduled time, at 2038 GMT, and had an original ending time of 0413 GMT Sunday.
Endeavor is to undock on Monday and return to Earth on Wednesday.
