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The 18 segments making up the primary mirror on the James
Webb Space Telescope will be held in place by something
called a backplane.
Since each hexagonal mirror is about three feet tall,
you can imagine this backplane plane is really huge and very
complicated to make.
To find out more about how this is being assembled,
we are here at ATK in Magna, Utah.
And we're happy to have with us Bob Hellekson.
He's the project manager for the James Webb Space Telescope.
Thanks for having us over.
Thank you for coming to visit us, Mary.
First of all, how tough a job is it
to make a backplane for the James Webb Space Telescope
well what we're standing in front of right
here is three of the full-scale hexes for the backplane.
And this was manufactured out of wood.
It established both of the tooling approach
and the assembly approach that we'll
use for the flight article.
Now you didn't just go from this to the real thing, did you?
No, we did not, as a matter of fact.
This structure was the first, made out of wood.
Then this same size, three hexes,
was made out of the graphite composite material.
It was taken down to the 30 Kelvin level or minus 405
degrees Fahrenheit.
And it was measured for its performance
on stability, meaning it had to stay
very stable through that entire temperature regime.
So, Bob, I understand the real backplane is here at ATK now.
Oh, absolutely.
We can show you that.
And we'll have to go in the clean room next.
I want to show you some electronic measuring equipment
to make sure that everything meets
its final dimensional performance before we deliver.
So is it like GPS where it detects where that ball is
located at any given time?
Yeah, that's exactly right.
That ball coordinates back on its surface
to where the model is for the corresponding feature.
This is very interesting stuff but the suspense is killing me.
Can we go see the backplane now?
Absolutely, let's step around this side.
And we'll show you the rest of it.
Great.
This is the center section of the backplane.
And it will house 12 of the primary mirror segments.
You said center section.
It's not the whole thing?
Correct.
The full-sized mirror will have 18 segments.
And what's missing here-- that'll come later--
are two wings, each holding three segments
or three mirrors.
And why break it out into a center and two wings?
The launch vehicles don't have the dimensions
to accept the entire width.
So it has to fold up.
And that's another unique feature
here-- is we're deploying three of the hexes
on each side or both wings.
This is not exactly a flat structure.
It looks like it's got a little bit of a curve.
That's correct.
The backplane matches the parabolic shape
that they want the primary mirror to end up with.
Besides holding the mirrors in place
once James Webb is in operation, what else is the backplane for?
The backplane also provides stability
to the entire observatory.
So what's missing here-- and you'll see later--
is a backplane stability frame that
reaches up about eight feet off of this section.
It will house the instruments for the observatory
and provides a lot of the strength for the launch.
Well, thanks for showing us ATK's backplane.
Well, thank you very much for coming to visit us, Mary.
So as you can see, this backplane
will be ultimately thermally and structurally stable, important
for the 18-segment primary mirror to stay still
so that the James Webb Space Telescope
can take its wonderful images of the universe.
Thanks for joining us for this edition of Behind the Webb.
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