ASTRONAUTS from the space shuttle Discovery have used their final spacewalk at the International Space Station (ISS) to exchange a nitrogen tank, make further adjustments to the Japanese space laboratory Kibo and perform various other tasks, said controllers. "They accomplished all of the planned tasks, as well as many extras,'' NASA spokeswoman Kylie Clem said in an interview reported by Bloomberg. Astronauts Mike Fossum and Ron Garan used their six-hour mission to outfit Kibo which was delivered to the space station by Discovery on June 2, work which included refastening a video camera which had been removed for repairs and removing thermal covers from the lab's robotic arm. They also deployed shields on the lab to protect the lab from space debris, added Clem. A depleted nitrogen tank was also removed from the International Space Station by the astronauts and replaced with a new one. The tank is a necessary part of the cooling system for the ISS as the station's metal skin gets hot when the sun is shining on the station. The spacewalk, the third by Discovery's crew, was Fossum's sixth, Garan's third, the 112th spacewalk devoted to space station assembly and maintenance, and the 197th by U.S. astronauts, according to a NASA statement. Discovery is on the eighth day of its two-week mission. - The Tech Herald