U.S. astronauts have completed their third and final spacewalk for space shuttle Atlantis's STS-129 mission. NASA said during a five hour, 42 minute spacewalk yesterday Randolph Bresnik and Robert Satcher Jr. installed the seventh Materials International Space Station Experiment, or MISSE 7. This is the most advanced of the MISSE payloads and will be the first to receive power directly from the station and use the station's communication system to send commands and downlink real-time data. Atlantis lifted off from Kennedy Space Center in Florida on the 16th of this month. Its 11-day flight included three spacewalks and the installation of two platforms to the station's truss, or backbone. Atlantis' STS-129 mission is NASA's fifth and last shuttle mission for 2009.