The last of the planned tasks is possible the hardest: installing an upgraded powerunit to the International Space Station’s movable powered cart. Until now the MTRA cart could move objects along the Station’s truss but not keep them powered at the same time. The cart would stop at specific places where power was fed directly from the Station’s main power lines. With the upgrade Alexander and Reid will put it place, the cart can power the objects attached to it at all times. This is of special interest when it moves the Station’s robotic arm that Alexander used to move between the sites he worked on.
Their task is comparable to rewiring a car engine while wearing motorcycle gloves according to veteran ESA astronaut spacewalker Hans Schlegel. Reid will spend two hours on this task, while Alexander returns the robotic arm to its normal operational mode by removing the foot restraint adapter.
Alexander will no longer use Canadarm to get around. Once Alexander stows the Canadarm he will move to Reid and help him finish up work on the MTRA, working together for 75 minutes.
The task is mainly one of installing cables, connecting them and setting jumpers. Keep in mind that these cables must not be bent too sharply and they will float about in weightlessness like snakes.