Published: May 21, 2010 9:55 AM EDT
Updated: May 21, 2010 11:53 AM EDT

CAPE CANAVERAL, Fla. (AP) - The Atlantis astronauts have one more big job before leaving the International Space Station.

On Friday morning, two of the crew will venture out on the third and final spacewalk of their mission. Astronauts Garrett Reisman and Michael Good will finish installing new space station batteries. They will replace two old batteries. Four new batteries went in during Wednesday's spacewalk. A

tlantis delivered the batteries along with a new Russian compartment. The chamber was opened Thursday, but had to be sealed again when metal filings were found floating inside. Flight controllers are devising a clean-up plan.

Atlantis will undock from the space station Sunday for the last time. NASA has just two shuttle missions left.