Astronauts take 2nd spacewalk for ammonia refill

By MARCIA DUNN | May 22, 2011 | 2:14 AM EDT

This image provided by NASA shows the intersecting thin line of Earth's atmosphere with the International Space Station's solar array wings photographed Thursday May 20, 2011 by an STS-134 crew member while space shuttle Endeavour remains docked with the station. (AP Photo/NASA)

CAPE CANAVERAL, Fla. (AP) — Space shuttle Endeavour's astronauts are spacewalking again

Crew members Andrew Feustel and Mike Fincke floated out of the International Space Station early Sunday morning. It is the second of four spacewalks planned for Endeavour's final voyage.

Feustel and Fincke will add five pounds of ammonia to the space station's coolant system. One line is leaking slightly, and the astronauts will top it off. Ammonia is extremely hazardous, and the two will try to avoid contaminating their spacesuits.

The spacewalkers also will lubricate a large joint that rotates the space station's solar wings on the left side.

This is NASA's next-to-last space shuttle mission. The 30-year program will end in July with the flight of Atlantis.