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Images of the Mirrors

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Caption: Webb Telescope's Secondary Mirror Looks Like a Giant Sun

The round, gold coated secondary mirror that will fly aboard NASA's James Webb Space Telescope looks like a giant sun in this photo where technicians at NASA were securing it to a platform. What appears to be a track circling the mirror looks like the orbit a planet would take around the sun. The rounded shipping canister that the housed the mirror actually fit on that rounded "track."

Unlike the 18 hexagonal primary mirror segments that make up the biggest mirror on the Webb telescope, the secondary mirror is perfectly rounded. The mirror is also convex, so the reflective surface bulges toward a light source. It looks much like a curved mirror that you'll see on the wall near the exit of a parking garage that lets motorists see around a corner. This mirror is coated with a microscopic layer of gold to enable it to efficiently reflect infrared light (which is what the Webb telescope's cameras see).

"The thickness of the gold coating on the mirrors is only 100 nanometers thick, or a tenth of a micron, which is 1/10,000th of a millimeter," said Paul Geithner, Deputy Project Manager - Technical for the Webb telescope at NASA's Goddard Space Flight Center in Greenbelt, Md. "A human hair is roughly 1000 times thicker."

The mirror arrived at NASA's Goddard Space Flight Center in Greenbelt, Md. on Nov. 5, 2012. The mirror previously resided at Ball Aerospace & Technologies Corp. of Boulder, Colo. who manufactured it.

The Webb telescope is the world's next-generation space observatory and successor to the Hubble Space Telescope. The most powerful space telescope ever built, the Webb telescope will provide images of the first galaxies ever formed, and explore planets around distant stars. It is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

Credit: NASA/Chris Gunn

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