"All this preparation has made me slightly paranoid and for good reason. I am about to enter the large clean room at Ball Aerospace in Boulder, Colorado where the mirrors for the $8.7 billion James Webb Space Telescope (JWST) are being built and tested. These will enable us to look back in time 13.6 billion years to the immediate aftermath of the Big Bang. They will be precise enough to capture single photons. And the slightest speck of dust or greasy fingerprint could ruin them."
http://www.bbc.com/future/story/20130923-most-complex-mirror-ever-built
RICHARD HOLLINGHAM BBC.