U.S. astronauts Chris Cassidy and Tom Marshburn have embarked on a seven-and-a-half hour spacewalk to catch up on leftover tasks.
Cassidy and Marshburn are replacing four of six batteries that power the solar energy system on the International Space Station. Astronauts replaced two of the batteries during Wednesday's spacewalk, but the work was cut short, because carbon dioxide levels in Cassidy's spacesuit were rising. NASA said the spacesuit problem has been fixed.
Cassidy and Marshburn are also planning to install a camera on the "porch" of the Kibo module of the space station where experiments can be conducted while exposed to space. This had originally been scheduled for the mission's first spacewalk.
To cut down on preparation time this morning, Cassidy and Marshburn spent the night in the airlock entryway of the space station.
On Thursday, the space station and shuttle crew inaugurated the new robotic arm that operates the experiment station on the Kibo front porch.
There were some initial problems when the robotic arm moved faster than expected, but the astronauts made some adjustments to slow it down.
They were able to move equipment from the Japanese carrier to the exposed facility for all three planned initial experiments.