Truss spacer segment added to station during spacewalk
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: December 12, 2006
Astronauts Robert Curbeam and Christer Fuglesang re-entered the space station's Quest airlock module, sealed the hatch and began repressurizing at 10:07 p.m. to successfully close out the first of three spacewalks planned for the shuttle Discovery's mission.
The six-hour 36-minute excursion, the 74th devoted to station assembly and maintenance, pushes total space station EVA time to 450 hours and 50 minutes since construction began in 1998.
Including three spacewalks during a 2001 station visit, Curbeam has now logged 26 hours and 25 minutes of EVA time over four spacewalks, moving him to 21st on the list of most experienced spacewalkers. Tonight's outing was the first for Fuglesang, Sweden's first astronaut.
The primary goal of the spacewalk was to bolt a new solar array truss segment to the left end of the station's main power beam. The astronauts also repositioned a grapple fixture and replaced a faulty television camera on the opposite end of the truss. Finally, they performed a few minor "get ahead" tasks, including electrical connections between P5 and the P4 solar array segment and tests of a lock assembly, to save time for future assembly crews.
Before ending the spacewalk, Curbeam radioed congratulations to John Mather, a NASA astrophysicist at the Goddard Space Flight Center in Greenbelt, Md., who shared this year's Nobel Prize in physics for his work studying the remnant heat left over from the big bang birth of the universe.
"I just want to say congratulations to all the Nobel Prize winners this year and especially to John Mather of the Goddard space center," Curbeam said. "We're proud of you."
"Thanks to both of you for those very gracious words," astronaut Stephen Robinson radioed from mission control. "And from here on the ground, we'd like to extend our congrtatulations for a 100 percent successful first EVA. It was a real pleasure for us to watch it."
One concern going into today's spacewalk was tight clearance between the P5 spacer and a device called a sequential shunt unit, or SSU, on the P4 segment. The P4 arrays are not yet providing power to the station and most of the electricity being generated is being routed back into the solar cells by the SSU to be dissipated as heat.
Sunita Williams and Joan Higginbotham, operating the station's robot arm from inside the Destiny laboratory module, were relying on verbal guidance from the spacewalkers to guide P5 into position with just two inches or so of clearance.
"Ah, that's beautiful," Fuglesang said as P5 inched into position.
"Yes, it is," Curbeam agreed.
A few moments later, two guidance pins on Curbeam's side of the structure were in position while Fuglesang's were still slightly out of alignment. The arm operators then ran a procedure to use a bit more force to get all four guidance pins properly seated.
"We don't want to scream on the loops, but we're really happy," Higginbotham radioed when the last pin was in place.
"You're not the only one," Curbeam said.
The spacewalkers tightened the four bolts, attached electrical grounding straps and a wireless communications system connector to complete P5's attachment.
While the spacewalk was underway NASA's Mission Management Team met and decided against ordering any additional heat shield inspections by the shuttle Discovery's crew.
Earlier today, image analysts and engineers completed an assessment of post-launch heat shield inspection video and other data, along with an impromptu inspection late Monday to check the health of Discovery's left wing leading edge panels. Data from a sensor indicated a possible low-energy micrometeoroid hit on the outboard section of the leading edge earlier Monday.
In addition, photography by the station crew during Discovery's final approach to the outpost earlier Monday revealed some tile dings near an umbilical door in the shuttle's belly. But the MMT decided the damage was minimal and not a threat to the shuttle during re-entry.
As such, no additional "focused" inspections will be required Wednesday. The astronauts will, however, carry out a final heat shield inspection after leaving the station next week, as originally planned, to check for any signs of damage since the initial inspection was completed.
"Based on all the imagery gathered so far, no focused inspection is required," astronaut Kevin Ford radioed Discovery today during the first of three planned space station assembly spacewalks. "And the TPS (thermal protection system) is not suspect."
"Well that's outstanding news!" said shuttle skipper Mark Polansky. "I read the MMT summary and saw some of the pictures, so it sounds like you guys have obviously done your usual, thorough analysis and we're happy to hear we can go on with the normal timeline tomorrow."
"Good news for us, too," Ford said. "Hated to bother you during the EVA but thought you might be interested in that."
"I'd be really interested in that," Polansky said. "And then my understanding from that is that with regards to the wing leading edge system, everything else, we'll just kind of use late inspection as a confirmation or just a chance to go ahead and see if there were any problems we might have missed."
"That's absolutely right, that's the plan," Ford said.
"OK, well that's great," Polansky replied. "That'll give us a great start tomorrow for the solar array retract and we do have some tremendous views out the window to enhance that. So hopefully, that'll work according to the plan."
He was referring to the planned retraction of one side of the P6 solar arrays that have been providing power to the U.S. segment during the initial assembly of the space station. During two spacewalks Thursday and Saturday, the astronauts will switch the station over to its permanent power system. But first, the crew must successfully retract the P6-4B array. That's the crew's major objective Wednesday.