NASA astronauts prepared today for their fourth and final spacewalk during the space shuttle Endeavour's last mission to the International Space Station.
Much of the astronauts' focus today and Friday is on increasing the robotics capability of the orbiting space station before they head for home.
The Endeavour and its six man crew is 10 days into its 16 day mission to bring supplies, equipment and experiments to the space station. With three spacewalks behind them, the shuttle astronauts are gearing up for what will not only be the mission's last spacewalk but also the last spacewalk for any shuttle astronauts.
While space shuttle Atlantis is scheduled to make the shuttle fleet's final launch next month, the crew will not make any spacewalks. Instead, space station crew members will make the rest of the spacewalks, according to NASA.
Earlier today, members of the space shuttle crew used the robotic arm onboard the shuttle to perform one last inspection of the vehicle's heat shield and wings. This inspection usually is done after the shuttle undocks from the space station. However, since this is Endeavour's final trip aloft, spacewalkers will take the shuttle's robotic arm off the spacecraft and attach it to the space station, giving it one more piece of robotics to use.
The procedure isn't the only robotic work being performed on this shuttle mission. Endeavour also delivered a spare robotic hand and arm for the humanoid robot that was recently moved onto the space station.
On Wednesday's spacewalk, astronauts worked on Canadarm II, the main robotic arm on the space station.
During a six hour, 54 minute spacewalk, astronauts Drew Feustel and Mike Fincke installed a power and data grapple fixture on the Russian Zarya module. The fixture will act as a base or foot for Canadarm II. The robotic arm will be able to move much like an inchworm across the backbone of the space station. The arm will be able to reach out and grasp onto the new base, and then that base will become the arm's anchor so the other end can release its old base and become the arm's hand.
Moving on to this new base on the Russian module, will greatly extend Canadarm II's reach.
The spacewalk brought the total time spent for station assembly construction and maintenance to 995 hours and 13 minutes during 158 spacewalks, according to NASA. Friday spacewalk is expected to break the 1,000 hour mark.