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Mirrors on a telescope are often coated with some kind of metal
in order to reflect as much light as possible.
Now the type of metal depends upon the kind of light
the telescope is looking at.
The James Webb Space Telescope is looking at infrared light.
And for that, gold is the ideal choice.
To find out how the gold is put onto the mirrors of the James
Webb Space Telescope, we are here
at Quantum Coating in Moorestown, New Jersey.
So, Ian, how much gold are we talking about?
Enough for a ring?
Not even that.
Well, it depends on how big your ring is, of course.
But the thickness of the coating is almost unimaginably small.
To give an example, this piece of paper
is about one thousandth of an inch.
We could take 1,000 gold coatings,
stack them all side by side, and they
would be the thickness of this piece of paper.
In terms of the amount of gold that we need,
it comes to three grams of material.
And three grams looks like--
Three grams-- I have it here.
--this.
Wow, that's amazing considering how big the mirror is.
That in mind, when it's spread out thin enough,
it covers the whole surface of the hexagon.
When you apply the coating, are we talking about a paint job?
No, this is all vacuum deposition.
It happens in a chamber where all of the air
has been sucked out to create a vacuum.
Then we vaporize the gold.
We create a cloud of vapor.
And that vapor condenses on the surface to form the film.
And why do you choose to apply the gold that way?
That's the way to get the maximum reflection.
Spray painting or other techniques
wouldn't give us enough reflection.
And can we actually see the gold being applied to a mirror?
Sure.
Ty is the guy who operates the cutting machine.
He'd be happy to show you how that works.
Hey, Ty.
Hey, how are you doing, Mary?
I was told that a coating process is about to start.
Sure, we're about to start the coating soon.
Can we tag along?
Sure.
OK, see, what we're doing here now-- we're
preparing the mirror for coating.
Cleaning the mirror of any contaminants or any particles
that could be on the mirror.
So, Ty, what's going on here now?
OK, well, now we're putting on the shield and the mask
for the mirror.
A coating can not be beyond a certain area on the mirror.
So you want the gold to just be on the surface.
Nothing on the sides or anything.
Right.
There's a bevel also on the edge of the mirror.
We don't want any coating on the bevel either.
How long is it's going to take?
Maybe an hour in total.
But I understand there are no cameras in the chamber.
Can we see what's going on?
We can take a look inside our viewport.
We see the part rotating and we can see the glow dispersed
right now.
So, Ty, we couldn't show the actual company
specific equipment that was used to apply the coating,
but we get to see the gold-coated mirror,
fresh out of the chamber.
Yeah, that's neat.
Look at it.
The mirror is coated.
Now we're all complete.
And we're ready to ship it off to the customer.
And they can begin their testing.
Well, thanks so much for guiding us
through your coating process.
It was fascinating.
Well, not a problem at all.
Well, as you can see, gold isn't just
a fashion accessory for the James Webb Space Telescope
but a critical addition to making the telescope
work its very best.
Thanks for joining us for another edition
of Behind the Webb.
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