Two astronauts from the U.S. space shuttle Discovery have started (at 0848 UTC) a seven-hour spacewalk that will include the first ever in-flight repair to the orbiter's underside.
Mission specialist Steve Robinson will try to remove material that is sticking out from between some of the shuttle's crucial heat resistant tiles. The U.S. space agency, NASA, says astronaut Robinson is to stand on the end of the robot arm mounted on the International Space Station, where the shuttle is docked, and either pull out or trim the protruding gap fillers.
Another astronaut, Japan's Soichi Noguchi, also venturing out of the space shuttle is installing an external storage platform on the International Space Station.
Tuesday, NASA said it is looking into whether damaged insulation below the shuttle commander's cockpit window could break off during re-entry into Earth's atmosphere and strike Discovery. NASA officials say they will know more about the situation over the next day or two.
Some information for this report provided by AP.