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The James Webb Space Telescope
is a reflecting telescope,

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which means it images
of the universe

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with the help of mirrors.

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We are here at
L3-IOS-Tinsley in Richmond,

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California to find out just
how the observatory will work.

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So I'd like to first show
you one of our primary mirror

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segments.

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And before we get
too close, we'll

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want to put our mask on to
protect the optical surface.

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OK.

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This is one of our 18
primary mirror segments.

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Once they're all
complete, they'll

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combine to make one
large, primary mirror.

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You can see the front side
surfaces highly polished.

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And as we rotate to
the backside surface,

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you'll see that there
is a honeycomb light

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weighting so it reduces
the payload when it goes up

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into space.

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And yet, it's very stiff.

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It looks like you can
attach things to it too.

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Yes, they bond more hardware
on the backside surface,

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which makes it an even
stronger structure.

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And that's the way it'll
go up in the space.

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There are several other
mirrors that we're doing here

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for James Webb Space Telescope.

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We have a secondary
mirror element.

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We have a tertiary
mirror element.

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And we're also doing the
fine-steering mirror.

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For those of us who
don't understand

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how a telescope works, why
do you have so many mirrors?

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The light that comes
from space is collected

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into the primary mirrors.

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Primary mirrors then
take that light and image

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and bring it to the secondary
mirror, which projects it

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to the tertiary mirror.

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And then that goes to
the fine steering mirror.

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And then with
fine-steering mirror,

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they're able to adjust it,
and move it around, and get

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the images that
they're looking for.

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Why all the bouncing around?

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Well, the mirrors work together
to reduce the aperture size

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to a format that can fit on
a camera, that we can image.

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Now that we've seen
the primary mirror,

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I'd love to show you
the secondary mirror.

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So, Andrea, what's
going on here?

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We are performing a microscope
inspection of the surface.

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What he's doing
here is he's getting

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very close to the
optical surface

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so that he can
capture surface data.

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And then we can look
at that later on.

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And you can see
this one is unique

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compared to the other mirrors.

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This one is a convex hyperbola,
whereas the primary mirror

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and the tertiary
mirror are all concave.

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And there's only one of these?

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There's only one of these.

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So on the telescope
the light captured

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from the primary bounces
onto this next, right?

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Yep.

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That's why they call it
the secondary element.

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Two switches that
could pick two.

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We also have the
tertiary mirror,

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which is a concave ellipse.

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This is a onesie mirror,
just like the secondary

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and the fine-steering mirror.

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It's a one-of-a-kind
in the telescope.

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And with this mirror, we
run through the same sort

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of rigorous testing that
we do for the primary

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and the secondary mirror.

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And we get down to those
tight specifications

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that are required to maximize
the image resolution.

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Thanks a lot for
your time, Andrea,

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and showing us your mirrors.

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You're welcome.

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Andrea showed us a segment
of the primary mirror,

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the secondary mirror,
and the tertiary mirror.

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She wasn't able to show us
the fine-steering mirror.

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And that's the mirror that
keeps the beam of light

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collected by the telescope
centered and stabilized.

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That's because that
fine-steering mirror

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is inside this
thermal chamber going

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through some extreme
temperature changes

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to simulate the
conditions of space.

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Thanks for joining us
for another edition

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of Behind the Webb.

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