WEBVTT

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[LIVELY MUSIC]

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Because the Webb telescope is
too large to fit into a rocket,

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engineers have
designed it to unfold

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in a kind of
origami like fashion

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when it gets into orbit.

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That goes for the mirrors
on the Observatory too,

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the primary mirror that
collects light from the cosmos.

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Well, that light then bounces
up to the secondary mirror

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before making its
way to other mirrors

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and eventually ending
up into the cameras.

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We're here at NASA's
Goddard Space Flight

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Center in Greenbelt, Maryland
because the deployment

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of the secondary mirror
is about to happen.

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So, Adam, how do you guys
get the secondary mirror

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into position?

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Well, we deploy three struts
that are much like a tripod.

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And the secondary mirror
will sit above the backplane.

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So how important is this test?

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Well, this will
be the first time

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that we are deploying the
tripod with a secondary mirror

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installed.

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As with anything
on this project,

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every test builds upon another.

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So we want to be able
to master this test

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and be able to
perform it again when

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we get to the flight hardware.

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Well, can we take a closer look
at what's going on down there?

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Absolutely.

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Let's head into the clean room.

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You'll see the tripod
come into place

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just as I was saying upstairs.

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Now two of the
struts are the same.

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But one is actually different in
the sense that it has a hinge,

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and it folds underneath
when it's stowed.

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The entire Observatory
must be folded up

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so it fits in the Ariane 5.

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So the way you're doing
this test right now,

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this is not exactly the way it's
going to be in space, right?

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Yes, absolutely.

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This yellow tower effectively
creates a zero-g environment

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in the sense that it
doesn't allow the mid hinge

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to close on its own
when gravity takes over.

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We want to be able to control
every aspect of the operation

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of that closing of the hinge.

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Well, Mary, before the
deployment is complete,

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how about we go upstairs to
get a different perspective?

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But, first, we need to
put these blue masks

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on because we'll be in such
close proximity to the mirrors.

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OK.

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How big are these struts anyway?

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The distance between the
center of the backplane

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and the secondary
mirror is about 25 feet.

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So it's like a two-story
house or something.

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That's probably a
very good comparison.

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How strong are these struts?

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These struts are very
strong to withstand

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the stresses of very, very
cold temperatures of space.

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They are the hollow
composite tubes.

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And the material is
about 40,007 inch thick.

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So it's not very heavy?

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No, they're extremely light,
but they're also very strong.

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How precise do you have
to be with the positioning

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of that secondary mirror?

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Each time we deploy
the secondary mirror

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into the same position
that it will be in space,

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it is within 1
millimeter every time.

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Well, thanks, Adam,
for helping us

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understand more about
how the secondary mirror

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will be deployed.

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Thank you.

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It was my pleasure.

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The deployment of the secondary
mirror happens on the 11th day

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after launch and is
one of the last steps

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the Webb Telescope goes
through before it's

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considered fully deployed.

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Thanks for joining us for this
edition of Behind the Webb.

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[LIVELY MUSIC]

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