WASHINGTON – Two U.S. astronauts on Wednesday completed the first of three spacewalks scheduled for the space shuttle Discovery’s nine-day mission at the ISS, after overcoming several glitches.
With the help of the station’s robotic arm and guided by shuttle Commander Rick Sturckow and spacewalk choreographer Pat Forrester, the duo removed the bulky — albeit weightless in space — liquid ammonia coolant tank from the International Space Station’s (ISS) truss.
A new, 800-kilogram (1,760-pound) replacement will be installed during the second spacewalk late Thursday while the old tank will return to Earth with Discovery.
Astronaut Nicole Stott and Mission Specialist Danny Olivas returned to the orbiter’s decompression chamber at 0424 GMT after a spacewalk that lasted six hours and 35 minutes, NASA said.
Stott and Olivas also fetched U.S. and European experiment equipment from the orbiting station’s Columbus laboratory that will be brought back to scientists on Earth. The astronauts eventually won out over some stubborn bolts and pins.
The spacewalk did, however, hit a few snags.
Shortly before the halfway point, the pair lost communication for about 30 minutes with Mission Control in Houston, Texas as a storm interfered with communications equipment at a satellite relay station on the ground in Guam.
U.S. space agency officials downplayed the incident, saying it had not affected the safety of the flight.
"That’s not incredibly unusual. We try to plan around that kind of situation," NASA spokeswoman Brandi Dean told AFP from the Johnson Space Center in Houston.
"These spacewalks are very carefully choreographed, and the crew knows exactly what to do. Mission Control just looks over their shoulder . . . They don’t need communications input every step along the way."
Another concern emerged when Olivas alerted officials on the ground that he had some fraying on his glove.
As it turned out, he had only popped a stitch, which did not effect the outermost layer that keeps the air inside the spacesuit.
"It was pretty much a non-issue," Dean said.
Stott meanwhile noticed a high reading of her carbon dioxide levels. But teams on the ground later determined that it was a sensor problem that had not affected the function of her spacesuit.
Astronauts are scheduled to conduct two more spacewalks during the mission, the fourth of five planned for the shuttle program this year. The last is scheduled for November.
Tuesday, the Discovery’s seven-member crew — including Swede Christer Fuglesang — and the six ISS residents began unloading tons of equipment to the orbiting station, including popular U.S. talkshow comedian Stephen Colbert’s namesake treadmill.
The items were unloaded from the Leonardo Multi-Purpose Logistics Module, a huge pressurized chamber carrying 7.5 tons of supplies, including new station crew quarters, a freezer, food, two research racks and the Combined Operational Load Bearing External Resistance Treadmill (COLBERT).
COLBERT will be the second treadmill aboard the ISS. Exercise is key for astronauts spending long periods of time in space, where zero-gravity can result in muscle atrophy.
The freezer being delivered will store samples of blood, urine and other materials that will eventually be taken back to Earth for study on the effects of zero-gravity.
"Let’s face it, being weightless is mostly just a desperate bid to get away from the bathroom scale every morning," Colbert the comedian said in a video message to NASA before Discovery’s launch.
He originally won an online poll for NASA to name a new space station room after him but the U.S. space agency decided to instead name the new module Tranquillity and allow Colbert to have his name placed on the treadmill.
Stott is taking over at the ISS from engineer Tim Kopra, who has been aboard the orbiting laboratory since July and is slated to return to Earth with the shuttle.
Discovery blasted off from Cape Canaveral, Florida, Friday after its launch was delayed three times by bad weather and a valve problem. It is due to return to Earth on September 10.
The mission is the 128th for the space shuttle program, and the 30th mission to the ISS.
Once the Discovery mission is complete, just six more shuttle flights remain before NASA’s three shuttles are retired in September next year.
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