Launch from Cape Canaveral (KSC); landing at Cape Canaveral (KSC); ISS ULF-4 ICC, MRM-1 (now Rassvet), ERA.

The Atlantis astronauts used a less-capable backup sensor system to inspect the shuttle's carbon composite nose cap and wing leading edge panels after an overly-tight cable prevented them from using a more sophisticated, steerable sensor package. The crew lost several hours troubleshooting the problem because the backup system needs sun light, but the lead flight director said he was confident all the necessary data would be collected when all was said and done.

Following a two day solo flight Atlantis docked to the ISS on 16.05.2010. Joint operations with the ISS expedition 23.

First EVA by Reisman and Bowen on 17.05.2010 (7h 25m) to install a spare space-to-ground Ku-band antenna on the station's truss, or backbone. Then they installed a new tool platform on Dextre. The spacewalkers breaked the torque on bolts holding batteries in place on the truss, in preparation for their removal and replacement on the second and third spacewalks. Battery preparation work was deferred from STS-131 to this flight.

On May 18, 2010 the Russian Rassvet module was attached to the International Space Station. Kenneth Ham and Tony Antonelli maneuvered the shuttle robotic arm to unberth the module from Atlantis' payload bay and positioned it for handoff to the station robotic arm. Garrett Reisman and Piers Sellers were at the station arm controls to maneuver MRM-1 or Rassvet to its new position on the Russian segment. Expedition 23 Commander Oleg Kotov monitored the activities from the Russian segment as the MRM-1 engaged into its automated docking sequence for the final attachment to the station.

Second EVA by Bowen and Good on 19.05.2010 (7h 09m) to remove and replacing four of the six batteries on the port truss to store electricity from the solar arrays on that truss. The used batteries were installed on the cargo carrier for return to Earth on Atlantis. In addition to the original tasks Bowen and Good relieved a snagged cable that is preventing full use of the laser imager and video camera. The equipment is located on the Orbiter Boom Sensor System.

Third and final EVA by Good and Reisman on 21.05.2010 (6h 46m) to install the final two new batteries on the truss and put the old batteries on the carrier. Next, they retrieved a grapple fixture from Atlantis' payload bay and brought it inside the station for use as a spare.