Astronauts aboard Space Shuttle Atlantis are set for their second spacewalk Wednesday.  Astronauts will replace station batteries and fix a camera cable on today's spacewalk, the second of the mission.  

Astronauts will replace three batteries on the station port solar array. Each of the batteries weighs more than 360 pounds and will require an intricate choreography between the spacewalkers to swap out safely. The spacewalk is expected to last six and a half hours.