International Space Station during the second of five planned spacewalks.

This videograb released by NASA shows US space shuttle Endeavour Mission Specialists US Rich Linnehan (R) and US Mike Foreman (L) on March 15, 2008 at work outside the International Space Station (ISS) during the second of five planned spacewalks.

This videograb released by NASA shows US space shuttle Endeavour Mission Specialists US Rich Linnehan (C) on robot arm and US Mike Foreman (Up L) on March 15, 2008 at work outside the International Space Station (ISS) during the second of five planned spacewalks.

space shuttle Endeavour Mission Specialist US Rick Linnehan (L) rides a robot arm on March 17, 2008 out of the shuttle's cargo bay carrying a spare part during the third of five planned spacewalks.

space shuttle Endeavour Mission Specialist US Rick Linnehan (C) rides a robot arm on March 17, 2008 out of the shuttle's cargo bay carrying a spare part during the third of five planned spacewalks.

space shuttle Endeavour Mission Specialist US Rick Linnehan (C) rides a robot arm down into the shuttle's cargo bay to pick up a part on March 17, 2008 during the third of five planned spacewalks.

This videograb provided by NASA shows US space shuttle Endeavour Mission Specialists US Rich Linnehan (L behind robot) and US Mike Foreman (R) at work on March 16, 2008 preparing the Canadian Dextre robot (lower C) outside the International Space Station during the second of five planned spacewalks.

This videograb provided by NASA shows US space shuttle Endeavour Mission Specialists US Rich Linnehan (L) and US Mike Foreman (R) at work on March 16, 2008 preparing the Canadian Dextre robot (lower C) outside the International Space Station (ISS) during the second of five planned spacewalks.