At 5:04 a.m. EDT, space station robotic arm operators Jim Dutton and Stephanie Wilson attached a new Ammonia Tank Assembly (ATA) to the Starboard 1 truss, replacing a depleted ATA. Prior to that, spacewalkers Rick Mastracchio and Clay Anderson installed two radiator grapple fixture stowage beams on the port truss. Now, the spacewalkers will complete the ATA installation by engaging four bolts and connecting electrical cables and nitrogen and ammonia plumbing lines. Three hours, 34 minutes into the planned six hour, 30-minute activity, the spacewalk is on schedule.