GPS-III (Global Positioning System) is the first evolution stage of the third generation of the GPS satellites. It consists of the first ten (known as "tranche") of GPS III satellites. This spacecraft was original contracted to launch on United Launch Alliance's Vulcan rocket, and was reassigned to Falcon 9 following uncertainties in Vulcan's readiness to launch. As a result it was re-manifested within 6 months of launch under the name Rapid Response Trailblazer-1 (RRT-1). GPS III SV10, originally planned to launch on Falcon 9, will now launch on Vulcan instead.