WEBVTT FILE

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After launch, engineers on Earth
will need to make corrections to


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the positions of Webb’s primary
mirror segments to bring them


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into alignment.

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This will ensure they will
produce sharp, focused images.

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Webb’s primary mirror segments
can be adjusted in extremely

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minute movements.

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In steps of about 1/10,000th the
diameter of a human hair!

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Engineers determine how much
each segment must be moved

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through a process called
wavefront sensing and control.

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During this process, engineers
point Webb at a bright star and

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take 18 out-of-focus images of
that star, one from each


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primary mirror segment.

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They then use computer
algorithms to determine


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how much they must move the
mirror segments to align them.

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Alignment begins about 40 days
after launch, taking

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several months to complete.

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Once Webb makes observations,
its mirrors will be checked


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every few days to ensure they
are aligned.