Live In Orbit: Astronauts Step Through Spacewalk

Discovery's astronauts mounted a final segment to the International Space Station's central truss today and now are in the process of preparing the girder for the deployment of the outpost's fourth and final set of massive American solar wings.

With mission specialist John Phillips operating the station's Canadian-built construction crane, spacewalkers Steve Swanson and Ricky Arnold helped guide the 15.5-ton S6 segment to an attachment point on the starboard end of the central truss.

The spacewalkers then rigged up electrical and cables, and now they are preparing the segment for the deployment later this week of a set of solar wings that will stretch 240 feet from tip to tip.

Arnold aims to release restraints holding a large box that contains the folded-up solar blankets. The arrays ultimately will be unfurled like a venetian blind.

Swanson is setting out to prepare two radiator panels for deployment. That involves removing six cinches that keep the panels folded up together, and he'll remove two pins that prevent them from unfolded when stowed. Once that work is done, engineers in NASA's Mission Control Center at Johnson Space Center in Houston will send up computer commands that will result in radiator deployment.

Discovery's lead spacewalker then plans to move a beta gimbal assembly that will enable the solar wings to twist as they track the sun. A keel fastener keeps the assembly from moving during launch. Swanson will remove the fastener and rotate the assembly into place so that it can be unfolded. He'll also remove some launch restraints before reuniting with Arnold for another job: Rotating the blanket boxes into position for solar wing deployment.