13 mirrors polished for Webb telescope

NASA has completed coating 13 of the James Webb Space Telescope's 18 primary mirror segments, enabling the observatory to see objects as far away as the first galaxies in the universe. The mirrors were polished at L3 Integrated Optical Systems, Tinsley in Richmond, to accuracies of less than one-millionth of an inch. The space telescope is composed of four types of mirrors, primary, secondary, tertiary and fine steering. Made of beryllium, the mirrors will work together to relay images of the sky to the telescope's science cameras. Once polished, the mirrors are coated with a microscopically thin layer of gold that enables them to efficiently reflect infrared light. NASA plans to complete the coating of the remaining five mirrors by early next year. The 18 segments will fit together to make one large mirror that measures 6.5 m across. The mirrors have been developed by Northrop Grumman Corporation.