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[Music throughout] The Wide Field Instrument

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is the heart of WFIRST. The basic design is the same as

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telescopes around the world. Light enters through WFIRST's

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2.4-meter aperture, and is reflected and focused by the curved

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main mirror. Additional elements tighten the beam even more, and strip it

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of stray light rays before it passes through the filter wheel.

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This wheel has a variety of filters that allow different wavelengths of light to pass through.

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It spins from one to another depending on what the researcher

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is looking for. FInally, the focused and filtered light reaches the

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focal plane, where it creates an image on the detectors. In WFIRST's case,

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there are 18 detectors, allowing it to create 300-million-pixel

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images of large patches of the sky. 

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This 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

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in the future.