Webb Telescope's Secondary Mirror Unloaded at NASA Goddard
The secondary mirror that will fly aboard NASA's James Webb Space Telescope arrived at NASA's Goddard Space Flight Center in Greenbelt, Md., on Nov. 5, 2012. This photo shows the mirror housed in a shipping canister, being unloaded from a moving truck.
The mirror will reside in a Goddard clean room while technicians examine it.
The secondary mirror previously resided at Ball Aerospace & Technologies Corp. of Boulder, Colo., which manufactured and packed it.
Unlike the 18 primary 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 the curved mirrors on the walls near parking garage exits that let motorists see around corners. 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 quality of the secondary mirror surface is so good that the final convex surface at cold temperatures does not deviate from the design by more than a few millionths of a millimeter -- or about one ten-thousandth the diameter of a human hair.
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 study planets around distant stars. It is a joint project of NASA, the European Space Agency and the Canadian Space Agency.
Image credit: NASA/Chris Gunn
› More on Webb's secondary mirror
› NASA's Webb telescope website
› Webb telescope project website