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[Music Throughout]

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The Wide Field Instrument is the heart of WFIRST.

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It is what allows WFIRST to take pictures with the same detail as Hubble,

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but covering an area 100 times larger. Despite

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this incredible power, the basic design is the same as telescopes around

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the world.  Light enters through WFIRST's 2.4-meter aperture

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and is reflected and focused by the curved main mirror, which is

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also the largest mirror in the telescope. This light is reflected

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and focused once more by the secondary mirror. Additional elements tighten

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the beam even more and strip it of stray light rays before it passes through

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the filter wheel. This wheel has a variety of filters that allow

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different wavelengths of light to pass through. It spins from one to another 

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depending on what the researcher is looking for. Finally, the

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focused and filtered light reaches the focal plane, where it creates an image on the detectors.

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These detectors use the photoelectric effect to convert photons

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into an electrical signal that is then then decoded into an image.

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In WFIRST's case, there are 18 detectors, allowing it to create

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300-million-pixel images of large patches of the sky.

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The large number of detectors and pixels gives WFIRST

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its wide field of view. The size of the mirror and the precision of its optics

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gives WFIRST its fine imaging. This

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combination of image size and detail has never been possible on a space-based

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telescope before and will make WFIRST an indispensable tool in 

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the future.

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[Explore: Solar System & Beyond]

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[NASA]