A tear occurred in one of the International Space Station's (ISS) solar array wings during unfurling on Oct. 30, 2007. STS-120 astronauts George Zamka and Stephanie Wilson discovered the tear, but IS commander Peggy Whitson called for the halt to the unfurling operation started by mission control at Johnson Space Center.
Credit: NASA TV
HOUSTON — Two spacewalking astronauts reattached a massive solar power plant of the International Space Station (ISS) today, and inspected gears that orient its wing-like arrays toward the Sun.
But during NASA mission control's unfurling of wing-like solar arrays on the relocated power plant, the right wing of the 4B solar array crinkled and tore on one edge. The array opposite of 4B, known as 2B, deployed without incident prior to 4B's unfurling.
Astronauts aboard the space station were watching mission control's unfurling of the arrays, when ISS commander Peggy Whitson told mission control to abort the operation. The massive station piece with attached arrays was successfully reattached during today's spacewalk, which began at 4:45 a.m. EDT (0845 GMT) and ended at 11:53 a.m. EDT (1553 GMT).
"We just saw the tear and stopped," Whitson told ground controller and shuttle capsule communicator Kevin Ford after the tear was noticed. She added that the astronauts aboard the orbital laboratory could not clearly see the solar wing during part of the deployment because the sun's glare blocked their view.
"It looks like the damage appeared fairly suddenly," said space shuttle Discovery commander Pamela Melroy, who arrived with her STS-120 crew on Oct. 25.
Mission controllers said about 25 meters (82 feet) of the 35-meter (115-foot) electricity-generating array was deployed before the unfurling was halted.
It is uncertain at this time how the tear will impact the solar wing's energy gathering ability, which the space station's successful construction partly depends on. Astronauts have begun easing tension on the array to see how the damaged area responds.
Prior to accidental damage to the solar wing, however, orbital construction workers Scott Parazynski and Doug Wheelock successfully completed today's spacewalk, which lasted seven hours and eight minutes. Parazynski and Wheelock reattached the 35,000-pound (15,875-kilogram) Port 6 (P6) solar truss segment to the end of the orbital laboratory from which the solar arrays were later deployed.
After the behemoth truss segment was attached, Parazynski scoped out a set of gears that orient the station's solar panels toward the Sun. The port-side gears are working normally, but NASA engineers want to compare them to a similar yet misbehaving mechanism at the other end of the space station.
"I have a happy story so far," Parazynski said as he looked under a solar cover to the paddle-like joint containing the gears. "They look like they're brand new machines."
"It's going to help a lot with the diagnosis we've been making," said mission controllers here at Johnson Space Center as Parazynski relayed video images of the gears to Earth.
The report is a stark contrast that made by space shuttle Discovery astronaut Dan Tani, who found unusual metallic grit coating the gears of the 10-foot (3-meter) diameter starboard joint.
"It looked like a black dust of metallic shavings or filings," Tani said of the grit during an in-flight interview Monday. "It was unmistakable that it should not be there."
The unwelcome discovery prompted officials to extend the mission by one day, which will make room to replace a short spacewalk with a long, more complete check-out of the suspect starboard joint on Thursday.
Today marked the third of five record-tying extravehicular activities, or EVAs, planned during the STS-120's 15-day mission. It was Parazynski's sixth EVA and Wheelock's second.
The space shuttle Discovery is scheduled to land on Nov. 7 at Kennedy Space Center in Cape Canaveral, Fla. The spaceship will ferry ISS crewmember Clayton Anderson back to Earth, leaving Tani to take his place as a member of the Expedition 16 crew led by Whitson.
- SPACE.com Video Interplayer: Delivering 'Harmony' with NASA's STS-120 Mission
- NASA: Shuttle Launch Paves Way to Larger Space Station
- Complete Space Shuttle Mission Coverage