Astronauts on the space shuttle Atlantis are to make their first spacewalk today. <br/><br/>Mission specialists Garrett Reisman and Steve Bowen will venture outside the platform for about 6.5 hours to install an antenna and a robot tool tray. <br/><br/>Atlantis arrived at the station yesterday following a picture perfect launch from Florida on Friday. The ship's crew of six are spending the next week at the 350km-high outpost. <br/><br/>Other key tasks will include the replacement of six large batteries and the addition to the underside of the platform of a Russian docking and storage module. <br/><br/>Atlantis is undertaking what many expect to be its last mission before retirement. <br/><br/>After it returns from the station, Atlantis will not go straight to a museum. It will be prepared as a standby vessel ready to go to the rescue of the astronauts on November's flight of the Endeavour orbiter should they get into trouble.