The Webb telescope will see infrared light, which humans perceive as heat. In order to work properly, the telescope has to be kept very cold. Engineers have designed a huge sunshield to block heat from the Sun, allowing Webb to operate at nearly -400 degrees Fahrenheit. The telescope will be cold enough to let astronomers measure the infrared from faraway objects in the universe.
Engineers at Northrup Grumman in Redondo Beach, Calif., designed Webb's sunshield. It consists of five layers of a space-age material called Kapton. Each layer is only about as thick as a human hair, but has to be strong enough to withstand the harsh environment of space. The orientation of these layers also helps dissipate any incoming heat before it has a chance to affect the telescope. The sheets of the sunshield will be coated with different materials, depending upon their position. The two layers exposed to the Sun will be coated with silicon to reflect the Sun's energy. The remaining three layers will be coated with aluminum to reflect any residual heat that the first two layers were unable to dissipate.
Webb’s Big Chill
Publication: December 31, 2009