At NASA's Kennedy Space Center in Florida, Space Shuttle Endeavour is illuminated by bright xenon lights on Launch Pad 39A after the rotating service structure (RSS) was moved away. The structure provides weather protection and access to the shuttle while it awaits lift off on the pad. RSS "rollback," as it's called, happened in the evening of 28 April. STS-134 will deliver the Express Logistics Carrier-3, Alpha Magnetic Spectrometer-2 (AMS), a high-pressure gas tank and additional spare parts for the Dextre robotic helper to the International Space Station. Endeavour was scheduled to launch on 29 April, but that attempt was scrubbed while engineers assess an issue associated with the shuttle's Auxiliary Power Unit 1. STS-134 will be the final spaceflight for Endeavour.