The final spacewalk of NASA’s 30-year shuttle program is underway.
American astronauts Ron Garan and Mike Fossum stepped outside the International Space Station Tuesday to begin the walk, which should take about six-and-a-half hours.
The operation involves retrieving a broken ammonia pump from outside the space station and installing a robot used for refueling and repairing satellites.
The four astronauts aboard the recently arrived space shuttle Atlantis are assisting with the spacewalk.
In other developments, NASA said a piece of Soviet space debris it has been tracking poses no risk to the space station or shuttle. There had been concern the debris could collide Tuesday with one of the spacecraft. The debris is expected to make its closest approach during Tuesday’s spacewalk.
The Atlantis crew arrived at the ISS on Sunday to deliver more than four tons of spare parts, equipment, food, and other supplies that will sustain space station operations through 2012.
Upon its return to Earth next week, Atlantis will be retired and the U.S. space shuttle program will end after three decades.
NASA is stopping the shuttle program to concentrate resources on deep-space exploration. The agency is working with several commercial U.S. aerospace companies to develop vehicles to replace the shuttles. Until then, Russia’s Soyuz spacecraft will ferry U.S. astronauts to and from the space station, while Russian, European and Japanese cargo spacecraft will continue their resupply and waste disposal missions to the station.
Some information for this report was provided by AP.