Spacewalkers begin work on coolant loop

Endeavour spacewalkers are beginning preparations to refill an ammonia coolant loop on the International Space Station that has a slight leak.

The ammonia will be refilled during the mission's second spacewalk planned Sunday. Fluid will be pumped along the left side of the station's football field-length structural truss, from a segment near the center out to the far left side.

Before the ammonia can flow, the spacewalkers must install jumper cables between two segments in between, the Port 3 and Port 4 segments.

After Drew Feustel bolted a cover to a joint that rotates a pair of starboard solar array wings, he worked his way to the left side of the outpost.

Chamitoff installed a light on a rail cart, then had to recharge his oxygen supply, which NASA says is not uncommon for a first-time spacewalker.

The spacewalkers are running slightly behind schedule, but NASA says the time could be made up or the spacewalk could be extended beyond the planned duration of six-and-a-half hours. Both spacewalkers now have ample supplies of consumables to go the distance.

Later, they'll install an wireless communications system antenna on the Destiny lab.