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Because the Webb telescope is too large to fit into a rocket,
engineers have designed it to unfold
in a kind of origami like fashion
when it gets into orbit.
That goes for the mirrors on the Observatory too,
the primary mirror that collects light from the cosmos.
Well, that light then bounces up to the secondary mirror
before making its way to other mirrors
and eventually ending up into the cameras.
We're here at NASA's Goddard Space Flight
Center in Greenbelt, Maryland because the deployment
of the secondary mirror is about to happen.
So, Adam, how do you guys get the secondary mirror
into position?
Well, we deploy three struts that are much like a tripod.
And the secondary mirror will sit above the backplane.
So how important is this test?
Well, this will be the first time
that we are deploying the tripod with a secondary mirror
installed.
As with anything on this project,
every test builds upon another.
So we want to be able to master this test
and be able to perform it again when
we get to the flight hardware.
Well, can we take a closer look at what's going on down there?
Absolutely.
Let's head into the clean room.
You'll see the tripod come into place
just as I was saying upstairs.
Now two of the struts are the same.
But one is actually different in the sense that it has a hinge,
and it folds underneath when it's stowed.
The entire Observatory must be folded up
so it fits in the Ariane 5.
So the way you're doing this test right now,
this is not exactly the way it's going to be in space, right?
Yes, absolutely.
This yellow tower effectively creates a zero-g environment
in the sense that it doesn't allow the mid hinge
to close on its own when gravity takes over.
We want to be able to control every aspect of the operation
of that closing of the hinge.
Well, Mary, before the deployment is complete,
how about we go upstairs to get a different perspective?
But, first, we need to put these blue masks
on because we'll be in such close proximity to the mirrors.
OK.
How big are these struts anyway?
The distance between the center of the backplane
and the secondary mirror is about 25 feet.
So it's like a two-story house or something.
That's probably a very good comparison.
How strong are these struts?
These struts are very strong to withstand
the stresses of very, very cold temperatures of space.
They are the hollow composite tubes.
And the material is about 40,007 inch thick.
So it's not very heavy?
No, they're extremely light, but they're also very strong.
How precise do you have to be with the positioning
of that secondary mirror?
Each time we deploy the secondary mirror
into the same position that it will be in space,
it is within 1 millimeter every time.
Well, thanks, Adam, for helping us
understand more about how the secondary mirror
will be deployed.
Thank you.
It was my pleasure.
The deployment of the secondary mirror happens on the 11th day
after launch and is one of the last steps
the Webb Telescope goes through before it's
considered fully deployed.
Thanks for joining us for this edition of Behind the Webb.
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