Crew is preparing for critical spacewalk

HOUSTON — A pair of shuttle Atlantis’ astronauts will venture outside the international space station this morning to begin activating a $372 million set of power-producing solar arrays.

The critical spacewalk is the first of two planned to install the arrays, which is the primary goal of Atlantis’ 11-day flight. The solar panels are part of a 35,000-pound truss that eventually will double the station’s power supply.

Astronauts Joe Tanner and Heide Stefanyshyn-Piper are scheduled to exit the outpost’s airlock at 5:15 a.m. and work outside the docked ships for about 61⁄2 hours. The astronauts have been training for this day for more than four years.

“I don’t think tomorrow will be nerve-racking,” said Kirk Shireman, deputy manager of NASA’s station program. “It’s executing something that we’ve done hundreds of times (in practice).”

In preparation for the spacewalk, astronauts used the shuttle’s arm to hoist the massive truss from Atlantis’ cargo bay Monday and hand it to a similar arm on the station. Four motorized bolts automatically will attach the bus-sized structure to another station truss after it is moved into position.

Tanner and Stefanyshyn-Piper’s first priority is to hook up power and data cables so the truss can turn on heaters and survive the cold of space. The spacewalkers also will release launch restraints that will allow the 240-foot solar arrays to be unfurled from storage boxes late Wednesday.

Mission managers hope the activation of the truss goes as smoothly as the rest of the flight has so far.

With commander Brent Jett at the controls, Atlantis docked flawlessly with the station early Monday morning.