Two astronauts have conducted a spacewalk, the first of three scheduled for this week, to install a spare antenna on the International Space Station.

On Monday, Atlantis crewmen Garrett Reisman and Stephen Bowen also worked preliminary steps to replace 6 batteries later in the week. NASA wants to stockpile as much equipment at the space station before the shuttle program is retired later this year.

On Tuesday, the astronauts will work on another major job, attaching a new Russian compartment to the space station.