James Webb Space Telescope sunshield
Its intricate deployment was successfully completed on January 4, 2022, ten days after launch, when it was more than 0.8 million kilometers (500,000 mi) away from Earth.
Therefore, it was folded up to fit within the fairing of the launch rocket and was deployed post-launch, unfolding five layers of metal-coated plastic.
The outermost Sun-facing layers have a doped-silicon coating which gives it a purple color, toughens the shield, and helps it reflect heat.
Therefore, it uses a large sunshield to block light and heat from the Sun, Earth, and Moon, and its position near the Sun-Earth L2 Lagrange point keeps all three bodies on the same side of the spacecraft at all times.
[7] Its halo orbit around L2 avoids the shadow of the Earth and Moon, maintaining a constant environment for the sunshield and solar arrays.
If sunlight or the warm glow of the Earth heated the telescope, the infrared light emitted by the telescope would outshine its targets, and it wouldn't be able to see anything.The sunshield acts as large parasol allowing the main mirror, optics, and instruments to passively cool to 40 kelvins (−233 °C; −388 °F) or cooler,[6] and is one of the enabling technologies that will allow the JWST to operate.
[3][6] However the thin films are delicate – accidental tears during testing in 2018 were among the factors delaying the JWST project,[14] and Kapton is known to degrade after long term exposure to Earth conditions.
[6][3] This helps the material survive in space, radiate excess heat, and to conduct electricity, so a static charge does not build up on the layers.
The sunshield was hand-assembled at ManTech (NeXolve) in Huntsville, Alabama before it was delivered to Northrop Grumman in Redondo Beach, California for testing.
The reaction wheels, in turn, will eventually become saturated and require fuel to desaturate, potentially limiting spacecraft lifetime.
The trim tab, by helping keep the pressure balanced and hence limiting fuel usage, extends the working life of the telescope.
[23] The sunshield component attaches to the main spacecraft, and its booms expand outward spreading out the heat shield and separating the layers.
After a successful launch on 2021 December 25 from the Guiana Space Center, the post-launch deployment of the JWST sunshield proceeded as follows.
[25] Deployment of the left side boom (in relation to pointing direction of the main mirror) was delayed when mission control did not initially receive confirmation that the sunshield cover had fully rolled up.
