The Sunshield
The observatory is dominated visually by the sunshield subsystem, which separates
the observatory into a warm sun-facing side and a cold anti-sun side.
JWST will observe primarily the infrared light from faint and very distant objects.
But all objects, including telescopes, also emit infrared light in the form
of heat energy. To avoid swamping the very faint astronomical signals with
radiation from the telescope, the telescope and its instruments must be
very cold, at an operating temperature of under 50 K (-370 deg F).
The observatory will be pointed so that the Sun, Earth and Moon are always on one side, and the sunshield will act like a parasol, keeping the Optical Telescope Element and the Integrated Science Instrument Module cool by keeping them in the shade and protecting them from the heat of the sun and warm spacecraft bus electronics.
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In addition to providing a cold environment, the sunshield provides a thermally stable environment. This is essential to maintaining proper alignment of the primary mirror segments as the telescope changes its orientation to the Sun.
When fully deployed, the sunshield that will be about the size of a regulation
tennis court. |
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Here are photos of another engineering model of the sunshield, called the pathfinder. Read more... |
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Here are two videos showing the sunshield tests on the engineering model of JWST. |
