The 18 mirror segments will form the National Aeronautics and Space Administration's largest space telescope mirror -- more than seven times larger than the Hubble Space Telescope's mirror.
The Webb Telescope will have a 6.6-meter (21.65-foot) diameter primary mirror. Since it cannot be assembled on Earth and then fit into a rocket, the 18 mirror segments are designed to fold, much as leaves on a drop-leaf table. They will then be unfolded in space.
The completed primary mirror will be more than 2 1/2 times larger than the Hubble's primary mirror, but will weigh roughly half as much.
"The James Webb Space Telescope will collect light approximately 9 times faster than the Hubble Space Telescope ...," said Eric Smith, the project's lead scientist at NASA headquarters in Washington. He said the Webb Telescope is expected to revolutionize studies of how stars and planetary systems form and evolve.