Live in Orbit: Mission's First Spacewalk Nears

Update, 5:49 p.m.: The spacewalk is officially under way, with the astronauts' spacesuits now switched to internal battery power.

Update, 5:47 p.m.: Spacewalker Danny Olivas has opened the Quest airlock's hatch.

Two astronauts are suited up and getting ready to step outside the International Space Station for the first of three spacewalks planned during shuttle Discovery's 8.5-day visit.

The station's Quest airlock is begin depressurized from roughly sea level pressure of 14.7 pounds per square inch to about 5 psi, at which point spacesuit systems will be checked before proceeding to vacuum.

Conducting the spacewalk are Danny Olivas, a veteran of two prior spacewalks in June 2007, and rookie Nicole Stott, a former Kennedy Space Center engineer and shuttle flow manager.

Olivas, whose call sign is "EV-1," will be wearing a suit with solid red stripes on the legs. His helmet camera view will show No. 18 in the bottom right corner.

Stott, answering to "EV-2," will wear a suit with broken red stripes. Her helmet camera view will show No. 16 in the bottom right corner.

The pair's main task during the planned 6.5-hour excursion is to remove a pair of depleted ammonia tanks attached to the Port 1 section of the station's central truss, near its center.

The large tank assembly, weighing nearly 1,300 pounds (inlcuding roughly 200 pounds of ammonia), will temporarily be held by the station's robotic arm until the second spacewalk, when a new one will be installed and the old one will be tucked in Discovery's payload bay.

Discovery pilot Kevin Ford and station flight engineer Bob Thirsk of the Canadian Space Agency will operate the station's 58-foot robotic arm from a station in the Destiny lab.

The tanks are part of the station's cooling system.

Also today, the spacewalkers will also remove two sets materials and microgravity science experiments from the outside of the European Columbus science laboratory for their return home.

Discovery mission specialist Olivas will team up with European Space Agency astronaut Christer Fuglesang for the next two spacewalks.

Stott flew up to the station on Discovery, which launched late Friday from KSC, but is now part of the station's Expedition 20 crew.

You can watch the entire spacewalk and ongoing mission activity live here on The Flame Trench. Click on the NASA TV still image on the right side of the page to launch a viewer.

The spacewalk is the 131st in support of space station assembly and maintenance since the first pieces of the outpost were launched in 1998.