World’s Largest Camera Lens

They've been telling us that everybody is a lot more on edge than they've really been the whole process, because this is a really high-stakes day.

Like, this is the best you in the house right here, is to see when this cover is lifted off, and we get to see the lenses.

Hey, I'm Diana, and you're watching Physics Girl.

That footage was a challenge to get because we had a short window of a few hours to make it to a warehouse in Menlo Park, California, to be there for the reveal of a pair of lenses going on the world's largest digital camera.

I traveled to SLAC National Accelerator Laboratory to join a very excited group of scientists and engineers working on the camera.

And why did I want to see these lenses so bad?

Well, one reason is that no one ever gets to see lenses like this.

Perfect, massive pieces of glass like this are usually kept in clean rooms, away from mere mortals like us because these are not ordinary camera lenses.

This lens system is two lenses, and the whole system together costs $20 million.

And these lenses will become part of the camera going on the Large Synoptic Survey Telescope which is the latest telescope that's going to attempt a giant sky survey.

Sky surveys are like taking giant panorama photos of the whole sky.

OK, so imagine the sky is a jungle, and you're looking for a cougar or something like that.

You have the whole picture.

But then the LSST is going to take this panorama photo of the entire sky in the Southern Hemisphere every three nights, approximately, for 10 years.

We will collect more data in the first year than every other telescope combined has ever collected.

And then we'll do that for 10 years.

Ever in history?

Yes.

Yes.

That is insane.

Like, ever.

So you could hypothetically see how the whole population of cougars has changed, or something like that.

But first, you need a camera for your telescope.

And for that, you need some perfect one-of-a-kind camera lenses.

So this is like the only chance to see the lens because it's just going to be covered and-- Correct.

Yes.

Well, we feel very lucky.

It's good.

I'm glad you're here.

Our goal is to stay out of everybody's way, do nothing wrong, and not mess anything up.

You're correct.

There is definitely nerve-- There's a lot of nervous energy today.

There was a lot of nervous energy.

The head scientists and engineers were lying on the floor to get a good look, and people were being really careful, even before the lens was unveiled.

So we just got a safety debriefing where we were told what to do if the giant Dewar of liquid nitrogen spilled all over the floor, or in case of earthquake.

So we're prepared.

Everybody's here.

There is a crowd.

It's great.

As they lifted off the lens cover, they had to use an overhead system with strong polyester straps, and had to keep the cover sliding along vertical poles, so it didn't swing and accidentally bump the lenses.

Any bump could be catastrophic to these lenses.

The first thing that was unveiled underneath very slowly was the L2, the smaller of the two lenses that you can see here.

I thought that was it, but the more impressive lens, the L1, was still to come.

The L2 and L1 are all part of a system designed to make the best crispus-- is that a word?-- crispiest images possible.

If you were to put a golf ball at the same distance away from Earth as the Moon, we'd be able to see it with our camera.

The Moon is 80 million times bigger than a golf ball.

That's absurd!

DIANNA COWERN: They want really sharp images.

So they need a massive telescope with three giant mirrors, the largest of which is the size of a tennis court which, by the way, was only limited by the size of the tunnel that they had to transport it through to get to the Chilean mountaintop, which is where this telescope is going, by the way.

I was thinking, they're being so careful with everything.

And this lens is going in a telescope.

There's no way they're going to let us in the clean room.

But then they did.

And I'll show you guys the other hidden parts of the camera being assembled in the clean room.

But first, the L1.

[AMBIENT MUSIC] I feel like you don't get to see this part of the process of science very often.

You see the end result of science, usually.

But you don't see to the process.

You don't see the incredibly impressive equipment that's made.

That's the second reason I was so excited to be there.

We got to experience such a hidden part of the process of science.

So we're looking at this piece of glass and we're like, wow, that's beautiful, what a piece of equipment.

But it is easy to forget that this is a camera lens.

Usually, camera lenses look like this, or like this.

The one we were looking at, that piece of glass, is a five-foot marvel.

It looked like a perfect water droplet.

These lenses are made of fused silica, which is a material often used in fiber optics due to its purity and the fact that it's transparent to a wide range of colors of light.

Which makes it perfect for astronomy, where you want to see infrared, ultraviolet, visible light, all different colors of light, coming from the stars.

That was really cool.

What took place next was a thorough inspection of the camera lenses for anything unexpected.

And then the lenses were covered up and tucked away in the corner of the room.

So this really was our only chance to see the lenses because then they're going to be put into the camera, and then you'll never see them because they'll be in a telescope.

While the lenses were awe-inspiring, I honestly think the most impressive piece of equipment was the 3,200 megapixel sensor.

250 times better than your iPhone.

It's a little more than half a basketball court with 4K TVs in order to display one raw image from our camera.

Let's go take a look at it.

Well, it's not assembled yet.

But let's look at what they've assembled of it so far.

We have to get in clean room garb because the sensors were being tested and assembled in the back of the clean room.

Those shiny black squares are the CCD sensors or charged coupled devices.

Whenever photons of light come in from a star or another source and hit the sensors, electrons are released from the material and they collect at the surface.

Electric charge then builds up relative to how much light hits each area, and the amount of charge is then detected and converted into a digital image.

But the telescope will be collecting light from a variety of very dim sources.

We're seeing incredibly dim light.

Like, any star that you can see with your eye would just totally saturate our focal plane.

Like, we are seeing so far beyond the human eye it's kind of absurd.

DIANNA COWERN: So you only get a small number of photons.

And so any stray electrons could ruin the image.

And one thing that always introduces chaos?

Heat.

So the whole thing needs to be cooled.

So we were talking earlier.

Everything is cryo-- I don't know what words you use.

What are the technical-- Tools.

Specifically, the sensor and electronics piece, the camera, all cooled down, all under vacuum.

Yes.

So the electronics are at minus 40 Celsius, and the sensors are at minus 100 Celsius.

In addition to this impressive sensitivity, the camera will be able to see visible light, but also light from the near ultraviolet to near infrared wavelengths using special filters.

So what are we aiming to see with this telescope over its 10-year run?

Well, a lot of things, because you could use it for whatever you want to look for in the sky.

But hopefully, something to do with dark matter.

And we take an image of the entire Southern Hemisphere sky every couple days, and you can plot really precisely where all the stars are, where all the galaxies are.

You can plot with such precision that, when planets and galaxies move in a way that you didn't expect, you can infer that there's other stuff here that you can't see, dark energy and dark matter.

Stuff that you can't see seems promising.

But scientists have other goals as well.

There are things called variable stars that get dimmer and brighter, and the reason is because they're oscillating.

And so you see a smaller or larger effective area.

And then, for things like asteroids, things pop in your field of view suddenly.

There's so much potential for the LSST.

But it has to be finished first.

Today was a huge milestone to see the lenses that for a long time were just an idea for these scientists.

So the day we visited was exciting.

It's pretty incredible just to see how real the camera's getting-- I've seen it on my tiny computer screen for four years now.

It looks so small, like, I could hold it in my hand, but it's actually ginormous.

I cannot wait to start seeing the results of this telescope, but I'm going to have to be patient because it's not scheduled to be completed until 2022.

In the meantime though, you can follow the progress of the telescope on the LSST website at LSST.org.

They're documenting the entire build process, and there's a lot more about the project that I did not get into.

So in the meantime, I will be here waiting, dreaming, probably happily physics-ing forever.

Thank you so much for watching.

Until next time.

Do I have to say "happy physics-ing"?

WOMAN: Yeah.

I just said it.

Just say "happy physics-ing."

Happy physics-ing.

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