The James Webb Space Telescope when launched in 2018, will possess mirrors seven times larger than those on the Hubble. Above a part of the Webb telescope in the vacuum chamber to be tested to withstand the cold temperatures of space. Image credit: NASA Goddard/Chris Gunn
The Optical Telescope Element (OTE) Simulator or OSIM wrapped in a silver blanket on a platform, at the Goddard Space Flight Center in Maryland, being lowered down into a vacuum chamber (called the Space Environment Simulator, or SES) by a crane to be tested to withstand the cold temperatures of space to –400°F.
James Webb Space Telescope compared with Hubble. Image credit: wikipedia
The mirrors undergo cryo testing at NASA Marshall. Image credit: Ball Aerospace