How Does The James Webb Space Telescope Work? - Smarter Every Day 262

this is my dad and he's about to finish this major job you've been working on which is the james webb space telescope sun shield for this james webb space telescope hey it's me destin welcome back to smarter every day the james webb space telescope is about to launch and this is a really big deal that people from all over the science community have been waiting on for years by the time you watch this video it may have already launched or may have been in operation for decades it doesn't really matter because today we are going to talk to a very special person and we're going to learn a lot about the james webb space telescope the james webb space telescope is too big to fit into any rocket payload fairing so in order to get it to space it has to be folded up and launched in this more compact configuration after launch is designed to unfold like origami and what i see is a series of precisely choreographed engineering miracles not only do you have to make sure all this stuff works but it has to happen after the incredibly violent vibration environment of a rocket launch projects like the james webb space telescope or the jwst as it's known takes so long to make and are in operation for so long it's incredible you just saw my dad and i would be fascinated with the james webb space telescope whether or not dad worked on it or not but the fact that he did makes it pretty darn special for me and in an upcoming video we're going to explore exactly what dad did on the sunshield because it's really cool and there's a lot to learn there but first i want to learn about what the james webb space telescope is how it works all the important things and we're going to do that by talking to a very special individual a number of years ago back in 2017 i had an incredible honor i was invited to goddard space flight center and i had the opportunity to speak with an incredibly important person working on the project dr john mather before we start this conversation i want to explain its importance to you if you could pick any human in all of history to explain the james webb space telescope to you you would pick dr john mather first of all he's an astrophysicist and a cosmologist and he actually won the nobel prize for physics along with george smoot for his work on the cosmic background explorer satellite what i'm trying to say is he understands the night sky like no other and astronomers have been looking for the center of the expanded universe for a long time and there is no sign of it imagine an infinite universe that is expanding into itself infinitely without boundary without a center without an edge the second reason you'd want to listen to dr mather talk about this is because he is the senior project scientist over the james webb space telescope and what that means is he represents the interest of science to the project managers over the project and given the fact that he knows all this stuff and the whole project is about science you can imagine how important that means his perspective is not only are we speaking to a brilliant mind who knows many many things he's also very kind for example when i'm doing the interview which isn't the best execution of an interview i've ever done i'm trying to film him in the side room of a little conference center my camera kept overheating and he was very patient with me as i hope you will be too it's just really really simple like we're talking about the most complex thing that humans have ever built in a very simple way and i'll interrupt throughout our little interview here and we'll have some little simple drawing conversations it'll be fun so let's do it let's go talk to one of the many brilliant minds working on the james webb space telescope and let's try to get smarter every day [Music] all right so this is dr john mather uh am i allowed to say nobel laureate yes all right yes indeed do you mind talking to me about james webb for a second happy to do that let's go ahead and get comfortable so um what i'm interested in doing uh with your permission is creating a video series about how the james webb space telescope works okay and you're the man correct well i'm one of the many i've heard i'm the original senior project scientist i've been told that you are the man and that you're very humble and you give credit to everyone i'm also proud of what we've done okay but yes it's obviously a team project okay it's a huge dream project that's right a special art of it uh here's the telescope and you can see that it's uh it's not like anybody else's telescope it's not like the little tube of the galileo looked through it's not like the hubble space telescope it is uh way out there in space it looks more like a solar energy concentrator and it has this huge hexagonal mirror made out of 18 smaller hexagons to collect the starlight or the galaxy light that comes from over here bounces off of that bounces off a little convex mirror up here and back back down into this uh black area which is the beginning of the instrument package is that called a cassegrain these two parts make it a cassegrain there's a third big mirror that you can't see that makes it called a three mirror and a stigmat telescope which is better say that one more time three mirror and a stigmat i'll have to go look at that yes it means that it gives a good image over a much larger piece of sky got it and so we really care about that um because we want a really good image and we have a big camera okay so i did have to look that up three mirror anta no nstigmat three mirror and a stick mat basically it means that light gets bounced off of mirrors three times before it gets to the instruments or sensors that are taking the picture each of those mirror balances is for a very specific reason the big mirror essentially is like a big bucket it collects all the light as is traveling through space and then they focus that down they wanted as big of a mirror as possible because that means they can get more light a bigger bucket so all this light reflects off that big concave mirror and is focused down onto the little secondary mirror in front of it think about it that is so much more light hitting that little mirror than if the little mirror was just looking out into space by itself all that light then goes deep into the telescope and is bounced off one more mirror and then it goes to what's called the fine steering mirror this mirror compensates for the movement of the spacecraft and kind of works like image stabilization and back here in the back and all these optics that's where all the astigmatism is taken out of the image three mirror and a stigma but there's a fourth mirror in there to like work like image stabilization got it the hardest thing for us to build was this giant mirror because it's made out of 18 pieces and they all have to be adjusted to the right place after we get upstairs into space so each of them is made out of beryllium which is very light and very stiff and holds its shape when it's cold that was our hardest thing to learn how to make them ultra light because each of these hexagons is something you'd be able to lift with your hands if we'd allow you to do it so they're really thin material and really really accurate behind the telescope mirrors are is the instrument package which has the cameras and spectrometers and we had to invent some things for that too we needed much better detectors uh the detectors are made of two flavors uh one called mercury cadmium teleride and one is called arsenic doped silicon and the combination of those two things give us the sensitivity to the whole wavelength range that we wanted to study and that didn't exist before well they existed but they weren't good enough they weren't sensitive enough and they weren't big enough gotcha so we really had to push on that other things that are obviously difficult as how are you going to make this big thing so what i'm pointing at here is the sun shield so it's made out of five layers of thin plastic coated with nettle cap ton cap on so the sunshine comes up from this side and it's all reflected away so only a little tiny bit of heat gets through to this side because we want the telescope to be cold and also very stable basically the telescope will be flown in such a way that the sun's rays are always hitting the bottom or the instrument side of the sunshield and leaving the mirrors in the shadow just like on earth when we only see the stars when our side of the planet isn't facing the sun which we call nighttime well with this big sun shield the web can create its own continual knight for the telescope one side of the telescope is always in the dark and the other side is seeing light which is a really interesting way to do this because typically you have to do thermal management systems to keep everything at the right temperature but when you keep the optics cold you don't have to worry about temperature fluctuations so you can set it the way it needs to be and you can let it do its thing this is a fascinating engineering problem and we'll talk about this more in a future episode things that are more ordinary we still have to think about on the warm side of the the sun shield is the spacecraft box that contains all the spacecraft electronics the power supplies the rocket engines the fuel tanks the transmitters and receivers and the computers everything that it takes to run the observatory it's on this side is that how you also position the spacecraft where like where are the reaction wheels for example we have reaction wheels in here that are used to point the spacecraft in the right direction um and we have rocket jets which are used to for two things one is to maintain the orbit because it's an unstable orbit the other is once in a while to unload the reaction wheels because the reaction wheels collect angular momentum and where do you get the angular momentum you get it from sunshine which pushes on the telescope and isn't totally balanced so the combination of those two things means you have to use fuel and that's the thing that sets the lifetime of the observatory okay that was a lot but we can understand it check this out reaction wheels are amazing and i did a whole video on them years ago that goes into depth but it's basically a way of orienting or pointing the spacecraft without using a rocket just like cats do you should probably go back and watch that one too one way i like to think about reaction wheels is motocross this video from way back shows it pretty well so a motocross racer goes flying up into the air and they're briefly kind of weightless like a spacecraft but riders are able to control whether the nose of the bike goes up or down by breaking or accelerating if they accelerate the back wheel the nose goes up because the reaction torque spins the bike in the opposite direction of the wheel and if they want to pull the nose down then they hit the brakes and all the torque of slowing down the wheel is redirected into the bike and it tilts down basically it's the same idea on a space telescope but instead of attaching motorcycles to it to turn it in different ways they have little electric flywheels that are always spinning and if they accelerate them or decelerate them the angular momentum is transferred to the telescope and they can spin and point the spacecraft very precisely in all sorts of directions using a combination of reaction wheels oriented in different directions the other thing that's fascinating about the james webb space telescope is we're trying to keep it oriented in a very specific direction but we're getting all this pressure from the sun it's called solar radiation pressure basically as light and radiation from the sun hit the telescope they actually apply pressure to it not unlike a sail it's a really small amount of pressure like a thousandth of a gram on a square meter of spacecraft but if you think about it if you're in zero g in the vacuum of space a small force can offset everything and you have to account for that it's a really big deal so way back in the back of it where you can't see it in this black section behind the mirror is a huge box full of instrumentation and the instruments include cameras and spectrometers to cover the entire wavelength that we can see which ranges from 0.6 microns which you can see with your eye out to 28 microns wavelength which you definitely cannot so we said the spectrum ranges from 0.6 microns to 28 microns that's a measure of the wavelength of the light they'll be able to detect this means the telescope will just be able to see the red portion of visible light but it will look deep into the infrared spectrum obviously there must be some huge advantage to focusing so much on the infrared spectrum and he's about to talk about that in a little bit so we also have spectrometers and spread out the starlight into the rainbow of colors and to to find out all the measures of what's going on inside the object so the first thing you want to know is what's it made out of so then you look at the uh what's called spectrum lines uh so the spectrum lines come from different chemical elements and molecules and just as you see when you look at the fireworks on july 4th here each different color comes from a particular chemical element or molecule but it's different though because you actually have shifting right yes how do you know that you're detecting the correct elements if you're redshifted you actually have to detect a pattern if you only see one line one spectrum line you cannot be 100 sure what it's making what's making it so you really need to find two or more if you really want to be sure you're seeing what you think you're seeing so but then this accounts for the fact that sometimes the objects coming toward us are going away from us or participating in the expansion of the universe as a whole which can change the wavelength rather substantially a thing that's going away from us has the wavelengths of light that we receive increased so the fractional increase is called the redshift so it can go from zero or even minus if the thing is coming toward us to large numbers and so far the farthest thing we've seen with the telescope has a redshift of 11 which means the fractal fractional shift is 11 means the wavelength that we get is 12 times what it was when it started oh so that's a multiplier that you're talking about oh wow so if you see uh for instance the lyman alpha line at 0.12 microns wavelength by the time we get it it's at 1.44 so this is why infrared is so important because everything has shifted that direction right so for studying the distant universe where the expansion has stretched out all the wavelengths you definitely have to have an infrared telescope to study the light that started out as ultraviolet so so quick question so if you've seen a shift of 11 times does that mean that you have a sensor on board that will sense beyond 11 times yes okay so our telescope depends on what wavelengths you started with right but if you started with that particular lyman alpha line from hydrogen um redshift of 11 is 12 times the original wavelength there's 1.44 microns got it so but suppose the universe has got things even further away so that we see even more expansion since that time uh we're set up to see uh and we think we might see objects out to a redshift of 20 or 30. are you excited about that yes nobody's ever seen them uh they are predicted uh we are fairly confident of some of those predictions okay my camera kept overheating but this is a good time to talk about redshift you've experienced this in a way with a siren in the doppler effect as a ambulance or siren comes towards you you experience a higher tone but as it passes you and moves away that tone gets lower the sound waves from the siren are compressed against each other as it comes near you so it appears to yours as if it's a higher frequency and the sound waves seem to be expanded as it moves away from you and your ears perceive it as a lower frequency the same thing happens with light so as light from a star that is moving away from us reaches us the way we see that light is an expanded version of that light like the tone from the siren drops the frequency from the light appears to drop and it moves from the visible spectrum down into the infrared spectrum so if we didn't look into the infrared range we couldn't see light that started out as visible lights on things that are moving away from us this is the red shift and in the universe that's ever expanding many of the objects we're looking at and looking for will be moving away from us so looking in that lower infrared spectrum is super important so this is a giant tripod there's three legs the hinge points here here here here under the one and this leg folds in half and here's a hinge point so uh to get this ready for launch we let pull this one out sideways so you can pull the mirror up here and the legs actually fold around behind the observatory wow so it just fits you had a glimmer in your eye when you said that that's kind of a that's a big deal yeah it's a big deal um it's one of many things they have to work when you watch of course everything is folded up for lunch everything has to unfold and do the right thing out there so of course the big question everyone has is are you sure it's going to work and the answer is of course you can't be sure but we are doing what we should be doing to make sure so what do you do well number one you have two of everything when you possibly can so you get two shots when you need them you rehearse everything you practice and practice and practice and you have grouchy people come to tell you when you're not doing it right that's really important because we hate doing it wrong even if we don't like being told what what are those people the quality assurance officers those are review panels we get peer reviews we get senior engineers that have done something related before and that have a good instinct about these things they say no don't do it like that uh do it some other way right and so but the most important thing is you test and test and test because there's no such thing as analyzing anything well enough that you can be sure you know you have destructive tests and non-destructive tests so how do you perform a test when you only have one test article well we actually made several test articles we made a pathfinder for the telescope with uh the carbon fiber framework uh and we put on two of the mirrors or even finally three and my camera overheated again at this point i'm starting to get embarrassed but don't worry about it this gives us an opportunity as the camera cools off to get distracted by cool things at nasa this interview took place at nasa's goddard space flight center in greenbelt maryland which is where they've been controlling the hubble space telescope for the last several decades i spoke to the hubble operations manager and got to see the actual control room that's a topic for another day but they do all kinds of awesome stuff here at goddard so you're going to make this space telescope and you're going to put it up into space you don't want the first time it sees a vacuum or near absolute zero on the sensor side you don't want that to happen for the first time in space so you got to try to simulate that on earth how do you do these incredibly physically challenging things here on one atmosphere on the surface of earth the answer is a huge thermal vacuum that was built at goddard back in the 1960s and it's incredible so they really a large vacuum and they they pump liquid nitrogen into it to uh to make it cold make it cold they could simulate the environment of space that's crazy so this is how you simulate space on the ground that's right that's a this is what it takes that's amazing i love the legacy look of it you know yeah it looks like a boiler that's great but backwards is made to keep pressure out instead of take pressure or contain pressure all designed on paper you know back in the 60s you think about it like that it's all analog okay so we're on the top floor now we are walking towards the top of the thermal vacuum chamber that's cool so do they actually put james webb in there uh some of the components before the assembly they would take some of the larger components in this one and then we have much smaller ones over there they test everything all the way down to the nuts and bolts these are also thermal vacuum treatments just also or just smaller oh this is for component level stuff correct gotcha that's bolts nuts and bolts and smaller assembly parts oh that's cool they've got the hydraulic diagram like integrated to the valves that's pretty neat what do you think that was printed you know oh wow my bad got a little bit distracted the next thing they want to test for are the launch forces that happen on the rocket they have a huge centrifuge at goddard and they can place instruments on that and simulate the g-forces that the telescope will see during launch it's pretty awesome and then there's the vibrations that'll happen during launch okay this is the shaker table so the aureon is going to shake violently what you have to do is you have to make sure that the telescope isn't going to break during launch so here at goddard space center check it out it's a really cool area here this is the way they test that they'll put the telescope here they'll mount it in position and they'll shake it violently to make sure that nothing falls apart nothing breaks here's some b-roll footage of them doing that the vibration testing you can see the telescope shaking okay i'm in a really neat spot right now this is the tent that they move james webb around with it's like a portable clean room and this is the sound chamber where they're gonna they're gonna acoustically load the thing what they're doing here is simulating the roar of the rockets which can get up over 140 decibels it can be very destructive so they've got this big chamber with speakers in it with a massive subwoofer and other speakers to blast it with sound that's a subwoofer up top this is the largest subwoofer in the country as far as i know so if you really want to drop the bass this is where you come [Laughter] the cool thing about a sound chamber is that the sound is different at different parts in the chamber because you get reflections and echoes off the wall for example if i have a sound wave going across and bouncing off the wall you might get constructive interference meaning you get a louder sound at different points and you might get a quieter spot so in order to test that you can see they have microphones hanging at different points in the chamber wow i'm going to get back behind this because i don't want to interfere with what they're doing these people are moving this tent by hand and they're where the way they're doing that is on an air bearing they've got compressed air pumped to the feet of the tent in a really flat surface floor and they're able to move the whole thing by hand here's a couple of really cool shots where you can see people moving the entire space telescope by hand within the portable cleaning room on a cushion of air can you imagine what you're thinking this is so rad so my camera's overheating is that a problem on this on the telescope uh the observatory doesn't overheat because it's it's facing outer space the whole telescope is protected from the sun shine from the earth and from the moon all the time by this giant sun shield and we chose the orbit especially so we could do that the lagrange point two orbit that we choose is actually the only place you can go where the single-sided umbrella that we build can protect the observatory completely from all of those things at the same time lagrange points are special points in space where when you have two orbital bodies interacting with each other there's these little special spots where things can kind of just balance they're right in the sweet spot where they're being pulled in two different directions at the same time and they just kind of hover there lagrange points are fascinating there are five lagrangian points for any combination of two orbital bodies since james webb sensors could be affected by earth's shine and moonshine l2 of the earth's sun system is the optimum place for it to be and dr mather is about to explain why how are you going to communicate with it if it's on the other side of the moon oh it's not we don't go to that exact spot okay and of course the moon orbits as well so so are you orbiting the lagrangian point the orbit around the lagrange point we don't don't go to it uh number one it's easier to get there number two um the watch point's in the shade uh it's actually right behind the earth and uh most of the sunshine is being blocked by the earth at that spot so you don't want to go there can you can you draw that for me on this piece of paper yeah so so sure here is the uh here's the sun over here here's the earth over here and not to scale but here out here is the lagrange point and we are going to be orbiting around the lagrange point like that just enough to get the sunshine around the earth yeah we'll be uh where's the moon it's the earth the moon is a lot closer in the moon my handwriting is not so good today but the the the range point is about four times as far from the earth as the moon is oh i see so we're we never have a problem with that gotcha and so i i didn't realize that you were choosing to orbit in it yeah yeah i thought the whole point was to yeah i guess no we need the sunshine why we don't want to go in the we need uh solar power to run the observatory okay i see you need the sunshine it also takes more fuel to get to do you not have a you know have an rtg on board no we don't uh there's no need for it that's hard to do so and we need several kilowatts of of electricity so where the where are the solar panels the solar panels are hidden in this picture but they are obviously going to be on the sun side of the of the big sun shield but a few kilowatts is actually small for a giant observatory it is so that's because what's over here on this side doesn't use anything much gotcha a little bit of energy to run the detectors i know you're excited about what's going to come out of the telescope yes indeed who knows what's out there that we've never guessed at we have wonderfully exciting things to work on that we know about uh the first stars and galaxies the first black holes how the galaxies grow how stars are being born today with planets around them and even planets around other stars and the outer solar system where we'll learn something about how solar systems work and maybe even how come the earth is special or not the web telescope will make beautiful pictures as well they will be different of course because we pick up light at different wavelengths but those beautiful glowing gas clouds we'll see them too just differently we are among other things trying to see through those glowing clouds to see what's inside so the stars that are being born inside you can't see them directly right now because that that dust and gas is obscuring them the infrared light that we will pick up can go right around those dust grains and see inside so our hope is that it'll look different and also beautiful so you're saying the infrared light can go through those dust yes uh infrared light uh well all light bounces off dust particles right uh but the longer the wavelength the less bounce i see so uh the infrared light can go through the clouds that enables us to see things oh that's a big deal yeah so so what we'll probably be seeing is we'll take infrared images and then we'll false color them so people can see these beautiful pictures that we've seen in the past yes that's exactly the plan yeah that's fantastic last question what are you going to do on launch day i'll either be at the launch site to cheer or i'll be back here to talk to the public i don't know which one will be that there's such a limited number of people can go to the launch site that the people who really need to be there should be there right but are you i mean that's going to be a very anxious moment for you i'm sure um no no um i don't get anxious about stuff i can't deal with can you can you can you kind of tell me why yeah so i'm not anxious about things because i know that we're doing the right thing to make the best possible plan so when somebody says we should worry about this we worry about it and then we make a plan so when you're 70 years old you get tired of worrying about stuff you just say we'll make a plan i see and you accept what happens yeah that's interesting that's interesting and so i really like that this is dr john mather and uh i cannot thank you enough this is just a pleasure to talk with you and look forward to seeing what you make i thought this conversation was fascinating on so many different levels i came into it expecting to learn about science and astronomy and like how different things worked but i left with a sense of it was like a nugget of wisdom that dr mather dropped on us there at the end think about it this is one of the most complicated things that humans have ever done there's a lot riding on this there is a tremendous amount of investment of time money human lives my family included there's a lot riding on this but when i asked him well aren't you worried he said no because i've made the best possible plan we've done our best and then he just releases it he's like he's literally going to let it ride on a rocket there's some deep wisdom there that i'm going to apply to my own life if the man that's over one of the most difficult scientific endeavors that humans have ever done can make the best possible plan and then not worry and then like emotionally release that to say we did our best let's see what happens if he can do that with this project how can i apply that to my own life anyway i thought that was amazing i thought it was super deep wisdom and perhaps that would be helpful for you as it is for me this episode of smarter every day is sponsored by kiwiko and what i like about kiwiko is they send a kit to your house when you get a subscription and it ignites the brain of a child that you love one of the cool things about the james webb space telescope is it was created by a bunch of kids that grew up learning how to solve problems so that's what kiwico does these kits are awesome everything you need is included in the box they teach really cool concepts in science technology engineering arts and math and we love them this particular one is a bottle rocket i don't know how it's gonna launch yet we're gonna figure out how this thing launches and have a lot of fun with it what is that citric acid okay what is this baking soda this particular one we're working on today is called a tinker crate but there are eight different subscription lines currently shipping to over 40 different countries you can get your first box for free by going to kiwico.com smarter launch in five four three two one [Music] ah i didn't land the cup the thing i love most about the cubico subscription is it encourages you to explore like yeah there's the experiment you do but there's also all kinds of other ideas included in the kit and you can do all kinds of things that are like coloring outside the lines if that makes any sense okay this time let's try something else i love it you will too go to kiwico.com smarter if you want this for your family or a kid you love i highly encourage it in an upcoming video we're going to learn more about the james webb space telescope from my dad who actually worked on the sunshield very excited to share this with you it was exciting for me to be able to go to see my dad do one of the coolest things that humans have done i don't know and it's my dad right i'm really excited about that so i'll share that with you in an upcoming video and i hope you enjoyed this interview with dr john mather i'm destin you're getting smarter every day have a good one bye

Channel: SmarterEveryDay

Views: 1,275,709

Rating: 4.9753084 out of 5

Keywords: Smarter, Every, Day, Science, Physics, Destin, Sandlin, Education, Math, Smarter Every Day, experiment, nature, demonstration, slow, motion, slow motion, education, math, science, science education, what is science, Physics of, projects, experiments, science projects

Id: 4P8fKd0IVOs

Length: 29min 46sec (1786 seconds)

Published: Thu Sep 30 2021

Reddit Comments

[u/VehicularGenocide]

Man that guys philosophy on making plans for potential problems and then not worrying about them because you already have a plan in place and you have done your best really resonated with me. It also sounds like it resonated with Destin too.

[u/Gweenbleidd]

Oh great... so now after so many years he casually says that his dad works on JWT... whats next, his grandad was a US president? Honestly this guy.

[u/SavageChemist]

“Therefore do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own.”

Never looked up the passage before today. Love science and love being explained in such an easy to understand way. Thanks Destin!!!

[u/rattleandhum]

/u/mrpennywhistle , what happens if any space debris were to impact on those very delicate berylium mirrors?

[u/freerider]

I want a "Deep field" image with this telescope!

[u/jacob0bunburry]

I loved this video. Thank you.

A tangential thought: Someday, I'd also love to see what goes into documenting such an epic thought/ idea/ [noun?], from initial thought to completion.

[u/meltingpotato]

the telescope's design made me worry about space debris but it seems the amount and side of the debris isn't that big of a worry and they already accounted for it

[u/xgnarf]

How can the telescope orbit around the L2 point? Doesn't orbital mechanics require a mass to orbit around? I understand that the L2 point balances the gravity from the sun and the earth to create a stable orbit that matches the Earth's orbit rate. But if you're not directly on the L2 wouldn't that just make the telescope orbit the sun slower than the Earth?

[u/ThunderTheDog1]

Defintely gonna watch this when i get home. Ive been waiting for James Webb to be launched forever