Grades 3–5 · Systems
How did Webb unfold a giant sunshield in space?
The James Webb Space Telescope studies faint infrared light. A warm telescope would give off its own infrared glow, hiding some faint signals. Webb therefore carries a sunshield about the size of a tennis court to separate a warm, Sun-facing side from the cold telescope side.
In the diagramA folded package becomes a thermal barrierFoldedSpread outLayers apartFive thinsheetsBooms openthe packageCold telescopeWarm sideSunlight meets the lower, warm sideReflective sheets and open gaps redirect heat
The whole shield could not fit in the rocket while open. Its five very thin sheets were carefully folded. After launch, support structures opened and long booms spread the folded material outward. Cables then pulled the sheets into shape and separated the layers.
The layers have reflective metal coatings. They block and redirect much incoming energy. Heat can radiate out through the spaces between the sheets, while the vacuum gaps limit heat passing from one layer to the next. One thick blanket would not behave the same way.
Deployment turned a compact package into a large, carefully shaped thermal barrier. It did not cool every instrument in the same way: Webb’s mid-infrared detector also needs a powered cooler. The sunshield makes the telescope’s cold environment possible.
About this explanation
Starting knowledge: Understand that sunlight warms objects and a folded sheet takes less space.
Sources
- NASA — Sunshield Successfully Deploys on NASA’s Next Flagship Telescope
- NASA Science — Webb’s Sunshield