Two polished test mirror segments for the James Webb Space Telescope being inspected by an optical engineer: one segment with the gold coating already applied, the other without.
JWST has a foldable mirror composed of 18 hexagonal-shaped segments mounted onto a framework that forms the spine of the observatory. This structure has two wings that can be folded to fit inside the launcher. Once in space, JWST will unfold and spread its wings. It will then be the largest astronomical telescope in space.