On July 10, 2008, NASA formally approved the JWST project to move into its implementation phase. This decision followed a successful Preliminary Design Review (PDR) in March 2008 and a Non-Advocate Review in April. While all the science instruments and the "long lead" items like the primary mirror segments are already being manufactured, this approval marks the transition of the program into "Phase C" (Final Design and Fabrication). Phase D covers system assembly, integration and testing and launch. Since portions of this work occur while other subsystems are still in fabrication, NASA aficionados refer to this entire period as Phase C/D. Operations (Phase E: the fun part!) begins after instrument checkout and the cruise to L2.