'Deploying both wings of the telescope while part of the fully assembled observatory is another significant milestone showing Webb will deploy properly in space. Performed in early March, this test involved commanding the spacecraft's internal systems to fully extend and latch Webb's iconic 6.5 meter (21 feet 4-inch) primary mirror. In order to perform the groundbreaking science expected of Webb, its primary mirror needs to be so large that it cannot fit inside any rocket available in its fully extended form. In a recent test, NASA's James Webb Space Telescope fully deployed its primary mirror into the same configuration it will have when in space. NASA's James Webb Space Telescope Full Mirror Deployment a Success