page_title: Sunshield (JWST)
section_title: Layers
hierarchical_section_title: Sunshield (JWST) / Layers
caption_attribution_description: English: Engineers and test technicians load shiny test coupons inside one of the vacuum chambers in the Environmental Test Facility at NASA's Marshall Space Flight Center in Huntsville, Ala. The coupons are made of the same material that will be used to fabricate the the sunshield that will protect NASA’s James Webb Space Telescope from heat that might interfere with the operation of its mirrors and infrared sensors. During a series of three tests, coupons were exposed to extreme hot and cold temperature over a period of several weeks. This simulated the conditions where the James Webb Space Telescope sunshield will operate a million miles from Earth. The first set of coupons has already successfully completed stress and structural analysis by ManTech International Corporation, the Huntsville company that is designing and fabricating the sunshields.
context_page_description: Sunshield is a component of the James Webb Space Telescope, designed to shield the main optics from the Sun's heat and light. This is part of a space telescope and it extends out unfolding a large metal-coated sheet of material post-launch. This material blocks the Sun's light and heat, so the telescope can see the faint light coming from stars and galaxies. The sunshield segment includes the layers and its deployment mechanisms, which also includes the trim flap.
  The layers of the sunshield provide an insulating layer for the optics and help dissipate heat. The shield has five layers and, each layer is roughly the size of a tennis court. Each layer is as thin as a human hair and is coated with aluminum for reflectivity. The purple color of some layers comes from the material silicon, the same material in most computer chips, which toughens the shield and which helps it reflect heat. The telescope uses the sunshield to stop itself from being warmed by infrared radiation from the Sun and other nearby planetary objects, which would otherwise inhibit normal operations of onboard instruments.
context_section_description: The layer nearest to Primary mirror, L5 is the only one with a line of sight to it, while the l5 layer closest to the Sun, is the only one that receives direct sunlight. The separation between layers, in the vacuum of space, prevents heat transfer by conduction and aids in radiating heat out of the way.
  The silicon-doping is what causes the purple hue of the areas covered with that material.
  The layers are designed so the Sun, Earth, and Moon shine on layer 1 almost exclusively, sometimes a tiny portion of layer 2, and on the other side that the telescope elements only see Layer 5 and sometimes a tiny amount of Layer 4.
  Layers:
  Layer 1
  0.05 millimeters (0.002 inches)
  100 nm (3.93 microinches) aluminum coating (Both sides)
  50 nanometers (nm) (1.9 microinches) silicon-doped aluminum
  Biggest area layer
  Layer 2
  0.025 mm (0.001 inches)
  100 nm (3.93 microinches) aluminum coating (Both sides)
  50 nanometers (nm) (1.9 microinches) silicon-doped aluminum
  Layer 3
  0.025 mm (0.001 inches)
  100 nm (3.93 microinches) aluminum coating (Both sides)
  Layer 4
  0.025 mm (0.001 inches)
  100 nm (3.93 microinches) aluminum coating (Both sides)
  Layer 5
  0.025 mm (0.001 inches)
  100 nm (3.93 microinches) aluminum coating (Both sides)
  Smallest area layer
  During development the Sunshield layer material was tested with heat, cold, radiation, and high-velocity micro impacts.
caption: Coupons of Sunshield test fabric being tested to see how they perform, 2012
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