Live In Orbit: Spacewalk Under Way At ISS

Two American astronauts are exiting the U.S. Quest airlock at the International Space Station, heading out on a 6.5-hour excursion aimed at capping construction of the outpost's central truss.

Mission specialists Steve Swanson and Ricky Arnold switched their spacesuits to battery power at 1:16 p.m., marking the beginning of the 12st spacewalk performed since the first two building blocks of the outpost were linked in low Earth orbit in late 1998.

The astronauts floated outside the hatch of Quest as the joined shuttle-station complex soared 220 miles above the Pacific Ocean near New Guinea.

Swanson and Arnold plan to mount a 31,060-pound S6 girder on the starboard end of the station's central truss and then rig up electrical, data and coolant lines. The truss segment is equipped with a fourth and final set of power-producing solar wings -- arrays that will double the amount of electricity available to run science experiments.

"Fantastic job, guys. Give us more power," station skipper Mike Fincke said as the astronauts ventured outside the outpost. "Good luck."

Lead spacewalker Swanson is wearing a spacesuit with red stripes on its legs and he'll be answering to the radio call sign "EV-1." Arnold is wearing an all-white spacesuit and will answer to the call sign "EV-2." Mission specialist Joe Acaba, a former Melbourne High School science teacher, is directing the spacewalk from inside the station.

You can watch the action unfold right here in The Flame Trench. Simply click the NASA TV box on the righthand side of this page to launch our NASA TV viewer and live coverage. Be sure to refresh this page for periodic updates.