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the james webb space telescope is a

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reflecting telescope which means it

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images the universe with the help of

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mirrors we are here at l3 ios tinsley in

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richmond california to find out just how

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the observatory will work

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so i'd like to first show you one of our

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primary mirror segments and before we

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get too close we'll want to put our mask

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on to protect the optical surface okay

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this is one of our 18 primary mirror

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segments once they're all complete

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they'll combine to make one large

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primary mirror

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you can see the front side surface is

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highly polished and as we rotate to the

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backside surface you'll see that there

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is a honeycomb light waiting

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so it reduces the payload when it goes

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up into space and yet it's very stiff

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looks like you can attach things to it

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too yes they bond more hardware on the

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backside surface which makes it an even

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stronger structure and that's the way

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it'll go up in the space

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there are several other mirrors that

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we're doing here for james webb space

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telescope we have a

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secondary mirror element we have a

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tertiary mirror element and we're also

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doing the fine steering mirror that's

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for those of us who don't understand how

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a telescope works why do you have so

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many mirrors

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the light that comes from space is

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collected into the primary mirrors

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primary mirrors then take that light and

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image and bring it to the secondary

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mirror which

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projects it to the tertiary mirror and

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then that goes to the fine steering

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mirror and then with fine steering

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mirror they're able to adjust it move it

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around and get the images that they're

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looking for why all the bouncing around

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well the mirrors work together to

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reduce the aperture size to a format

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that can fit on a camera that we can

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image now that we've seen the primary

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mirror i'd love to show you the

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secondary mirror

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so andrea what's going on here

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we are performing a microscope

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inspection of the surface what he's

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doing here is he's getting very close to

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the optical surface so that he can

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capture

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surface data and then we can look at

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that later on and you can see this one

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is unique compared to the other mirrors

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this one is a convex hyperbola whereas

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the primary mirror and the tertiary

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mirror all concave

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and there's only one of these

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there's only one of these

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so on the telescope the

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light captured from the primary bounces

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onto this next right yep that's why they

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called the secondary element

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two switches i could pick two

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we also have the tertiary mirror which

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is a concave ellipse

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this is a onesie mirror just like the

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secondary in the fine steering mirror

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it's a one of a kind in a telescope

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and with this mirror we run through the

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same sort of rigorous testing that we do

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for the primary in the secondary mirror

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and we get down to those tight

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specifications that are required to

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maximize the image resolution thanks a

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lot for your time andrew and showing us

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your mirrors welcome

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andrea showed us a segment of the

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primary mirror the secondary mirror and

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the tertiary mirror she wasn't able to

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show us the fine steering mirror that's

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the mirror that keeps the beam of light

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collected by the telescope centered and

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stabilized that's because that fine

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steering mirror is inside this thermal

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chamber going through some extreme

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temperature changes to simulate the

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conditions of space