Live In Orbit: Spacewalk Under Way At Station

Two American astronauts just headed outside the International Space Station, setting out on an excursion to prep solar batteries for replacement and the outpost for the arrival later this year of a massive new Japanese space freighter.

Discovery mission specialists Steve Swanson and Joe Acaba exited the U.S. Quest airlock at 12:43 p.m. as the joined shuttle-station complex flew 220 miles over the Earth.

Lead spacewalker Swanson, a veteran of three previous outings, is wearing a spacesuit with red stripes and is answering to the radio call sign "EV-1." Acaba, who is making his first spaceflight and his first spacewalk, is wearing a spacesuit with broken red stripes and is answering to the radio call sign "EV-3."

The astronauts switched their suits to internal battery power at 12:51 p.m., marking the start of the scheduled 6.5-hour spacewalk. Discovery mission specialist Ricky Arnold is directing the excursion from inside the shuttle-station complex.

The first order of business for the spacewalkers will be securing themselves to station structure with braided steel safety tethers designed to keep the astronauts from floating off into oblivion. Swanson and Acaba also are equipped with small nitrogen-gas jet backpacks that they could use to fly back to structure in the unlikely event that their safety tethers were to break.

The astronauts also will be gathering up tools that they'll use during the course of the second of three spacewalks planned during Discovery's stay at the station.

Then they will set out for the far left side of the station's central truss, which stretches 335 feet from end to end. Made up of 11 girderlike segments, the truss serves as the metallic backbone of the station. It supports the outpost's four massive American solar wings, the last of which was delivered and deployed by the Discovery astronauts after their arrival at the outpost last Tuesday.

Swanson and Acaba will be using pistol-grip power tools to break the torque on bolts holding U.S. power system batteries to the P6 -- or port 6 -- truss segment. The bulky batteries have been in orbit since December 2000 and will be replaced by spacewalkers on the STS-127 mission in June.

Later in the excursion, the astronauts will be working with working with a GPS antenna on the Japanese segment of the statio. The antenna will be used when the first Japanese HTV space freighter arrives with a load of cargo in September.

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

Click here to see and save your copy of the Flight Day 7 Execute Plan. It includes the crew's detailed timeline for the day.

The timing of all major mission milestones can be viewed in the latest revision -- Rev I -- of the STS-119 NASA TV Schedule