By Marc Kaufman
Washington Post Staff Writer
Tuesday, September 12, 2006
HOUSTON, Sept. 11 -- Two astronauts are scheduled to begin a key spacewalk Tuesday morning to begin the complicated process of attaching a 17.5-ton truss that the space shuttle Atlantis delivered to the international space station on Monday.
Atlantis arrived at the station at 6:48 a.m. Eastern time after what was described as a perfect docking. The six crew members were greeted by the three-man station crew of a Russian, an American and a German astronaut, and they all promptly began preparing for the first new construction on the station in more than three years.
On Tuesday, astronauts Joseph Tanner and Heidemarie M. Stefanyshyn-Piper are scheduled to spend more than six hours out in space, 210 miles above Earth.
The two entered the space station's airlock on Monday night to sleep in conditions that will prepare them for the spacewalk. "Camping out" in the airlock helps the astronauts begin the walks more quickly by cutting the time required for breathing exercises and other preparations.
The shuttle carried aloft the truss and solar panels that will be attached to the space station as part of a greatly expanded solar-power system. The long-delayed mission is essential to meeting the goal of completing the station by 2010.
With both vehicles moving at 17,500 mph, the docking was a delicate maneuver. It was made more complex because Atlantis's commander, Brent W. Jett, had to fire off the shuttle's steering thrusters repeatedly to flip the vehicle over. That allowed the space station crew to photograph its underside for NASA engineers looking for damage that could have been done to the spacecraft's heat shielding during liftoff, a procedure implemented after the loss of Columbia.
A piece of foam insulation from Columbia's external fuel tank damaged a wing during launch in February 2003, causing the shuttle to burn up as it returned to Earth, killing all seven crew members.
NASA managers said Monday that they were confident that there was no significant damage to Atlantis from Saturday's liftoff and that only one small piece of debris -- a cover from a thruster -- was seen falling off during the ascent. They said it did not hit the shuttle.
Three spacewalks are scheduled for the 11- or 12-day mission. Most of the attention will be focused on attaching the truss, a structure that was 45 feet long when stowed in the shuttle's cargo bay but will be extended to 240 feet in space. The crew used the shuttle's robotic arm to lift the truss gingerly from Atlantis's hold shortly after docking and transferred it to the space station's robotic arm.
The Atlantis mission was delayed for three years in the aftermath of the Columbia disaster and then endured almost two weeks of launch delays at the Kennedy Space Center because of a lightning strike, storms and mechanical glitches. NASA managers said that once the craft finally took off, however, it performed extremely well.
The massive solar-panel array is needed to power the existing station and two large research labs scheduled to be added in the years ahead. One of them was manufactured by Japan and the other by the European Space Agency.
When operational, the station will allow researchers to conduct extensive experiments on the effects of zero gravity. The American interest in the space station, which focused originally on a broader scientific agenda, is now largely devoted to supporting President Bush's goal of sending astronauts back to the moon and then to Mars.