When the immense sound of the Ariane 5 rocket rumbles across Europe's spaceport in French Guiana, it will signal the end of a journey decades in the making. Perched atop the rocket will be the James Webb Space Telescope (JWST), the most sophisticated and complex observatory ever constructed. An enormous mirror 6.5 meters across, consisting of 18 gold-plated segments, will be delicately folded to fit within the nose cone.