02-09-09 First Discovery mission spacewalk completed

Two US astronauts on Wednesday completed the first of three spacewalks scheduled for the space shuttle Discovery's nine-day mission at the ISS,removing a massive coolant tank.With the help of the station's robotic arm and guided by shuttle Commander Rick Sturckow and spacewalk choreographer Pat Forrester,the duo removed an old 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 on 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.Shortly before the halfway point of their spacewalk,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.US space agency officials played down 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 spokesperson Brandi Dean told AFP from the Johnson Space Centre 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.On 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 US talkshow comedian Stephen Colbert's namesake treadmill.The items were unloaded from the Leonardo Multi-Purpose Logistics Module,a huge pressurised 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).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.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