Webb Sunshield Like An Umbrella On The Shores Of The Universe

The James Webb Space Telescope has a unique shield to protect its sensitive instruments from the heat and light of the sun. The sunshield is like an umbrella popping open on the shores of the cosmos that allows the instruments beneath it to see far into the universe. Like a beach umbrella protects people from the sun's heat and ultraviolet radiation, the sunshield protects the telescope and the sensitive infrared instruments that fly beneath the Webb telescope's sunshield from our sun's heat and light. "Each of the five layers of the shield is less than half the thickness of a piece of paper. The five work together to create an effective SPF (or Sun Protection Factor) of 1,000,000," said John Durning, Deputy Project Manager for the James Webb Space Telescope Project, at NASA's Goddard Space Flight Center, Greenbelt, Md.

A new video takes viewers to Northrop Grumman's Astro Aerospace in Carpinteria, Calif. to understand the mechanics necessary to unfold the large tennis-court sized sunshield. In the 3:00 minute video, engineers are interviewed to explain how the new technology extends the sunshield in space and unfurls it before the Webb telescope attains orbit one million miles from Earth.

The video called "Stretching Webb's Wings" is part of an on-going video series about the Webb telescope called "Behind the Webb." It was produced at the Space Telescope Science Institute (STScI) in Baltimore, Md. and takes viewers behind the scenes with scientists and engineers who are creating the Webb telescope's components.

The large sunshield is 20 meters (65.6 ft.) by 12 meters (39.3 ft.). It is made of a material called Kapton that can be folded like a blanket. Kapton is a film developed by DuPont which can remain stable and strong over the wide range of temperatures, from 36K to 650 Kelvin (K) (-395°F to 710°F or -237 to 377°C), the sunshield will experience during its launch and deployment. Once on orbit, the sunshield creates a 330 K (243°F to -351°F) temperature differential between the hottest and coldest layers. Using multiple separated layers allows most of a layer's heat to radiate to space before it reaches the next one creating a substantial temperature drop from one layer to the next.

The Kapton membranes used on the Webb telescope are coated with infrared-reflecting aluminum. The lowest two sun facing sunshield layers are coated with a silicon-based conductive coating to prevent the buildup of an electric charge, and minimize the amount of absorbed heat from the sun.

When the sunshield is folded up, it is packaged on a large pallet. A boom system being developed at Northrop Grumman Astro-aerospace in Galita, Calif. pulls each side of the sunshield from the pallet. It deploys much like a telescoping radio antenna, or like a big beach umbrella that extends upward and pops into place.