HOUSTON -- Two of the 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, the primary goal of the shuttle's 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 space station for about 6 1/2 hours. The astronauts have been training for today 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 today's spacewalk, astronauts used the shuttle's arm to gently hoist the huge truss from Atlantis' cargo bay and hand it to a similar arm on the station. Four motorized bolts automatically will attach the bus-size structure to another station truss this morning 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 tomorrow.
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 yesterday morning. The crew spent much of the day preparing for today's spacewalk after the hatches between the ship and station were opened.
"They docked pretty much on time and that was the only thing they did on time [yesterday] because everywhere else they have been ahead of schedule by a significant amount," said Paul Dye, the mission's lead flight director.
There was more good news yesterday from engineers analyzing the health of Atlantis' heat shielding. The shuttle appears to have survived launch largely unscathed by debris from the ship's external fuel tank.
As Atlantis approached the station yesterday, the outpost's crew took photos of protective heat tiles on the shuttle's belly. A preliminary review of the pictures turned up no significant damage, only a trio of ceramic cloth "gap fillers" protruding from between the tiles. None was expected to pose a problem for Atlantis' return home.
Astronauts had used a sensor-laden boom to inspect the shuttle's heating Sunday. No serious problems were detected.
Photographs and video of Atlantis' launch appear to show seven events where the tank shed small bits of foam or ice. However, all of the debris missed the shuttle or struck the ship too long after liftoff to cause serious damage, mission managers said.
Michael Cabbage writes for the Orlando Sentinel.