Astronauts Michael Foreman and Randolph Bresnik switched their spacesuits to battery power this morning officially kicking off a planned six-hour spacewalk.They floated out of the International Space Station...The goals of the excursion are to install an experimental antenna package on the Columbus research module, move an electrical monitor from the right side of the station's power truss to the left, deploy a payload attachment mechanism and mount an external TV camera.This is the 135th spacewalk devoted to station assembly and maintenance since construction began in 1998, the 16th so far this year and the second of three planned by the shuttle Atlantis' crew.