Two astronauts left shuttle Atlantis today on another spacewalk to repair a failed component on the orbiting Hubble Space Telescope, according to dpa. The US space agency NASA said the spacewalk began at 9:45 am local time (1345 GMT). Astronauts Mike Massimino and Mike Good started the fourth spacewalk of the Hubble repair mission - and the second for the duo, who were already working Friday outside the shutte. Their main goal on Sunday is the repair of Hubble's Space Telescope Imaging Spectrograph, which was first installed during a 1997 servicing mission and was knocked out by a power supply failure in 2004. To make the repair, the two astronauts will have to replace a low- voltage power supply board, in which a power converter failed nearly five years ago. The repair is expected to be time consuming during a spacewalk slated for more than six hours. Massimino and Good are also scheduled to install new blanket-like thermal material, which is meant to extend Hubble's life span by protecting the satellite's electronics from temperature extremes.
