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preroll music
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Herald: Our next speaker has studied in Bielefeld,
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and he studied... laughterclapping
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what he did is: He studied laser physics.
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And now he is working at the Max Planck Institute[br]for extraterrestrial physics.
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And today he will explain you
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how it is possible to use laser light
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to enhance distorted images
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that were take from the earth
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of stars and galaxies and nebulars.
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So I want to hear a
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really loud and warm applaus
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for Peter Buschkamp with
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"Shooting lasers into space -
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For science"! applause
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All right! Thank you for the nice introduction
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Thank you, for coming here
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this evening.
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I'm very excited
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to speak at the conference.
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Finally I find a talk
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where I can contribute
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after all those years.
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I'm not going to talk about Bielefeld.
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You might want to hear something about that.
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I'm not allowed to tell you... right?
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Okay, so today I'm going to talk about
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a bit what is in my field
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of experties.
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If there is one thing
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I want to bring across to you
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then it is
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It's not about a single person
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showing this to you this evening.
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This is a team effort and a real team effort.
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So most of the images are done by
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a college of mine Julian Ziegeleder.
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And the PI of the project,
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so the leader of the project
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Sebastian Rabien
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has contributed some slides.
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And I wouldn't be standing here today
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and showing you these images
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if it wasn't for a huge team
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and many people.
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I hope this is reasonably complete,
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but I think there were even more.
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Many people have tributed most and
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long years of there career into such a project.
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So this is never about something
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which a single person does
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and he or she finds something very cool
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and then saves the world.
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No, it's always a big, big team!
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But before we actually see the lasers
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then in working, we have of course to clarify
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why we do this.
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This is not just because we can.
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We can! But there is a reason for that,
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because if you want to get funding,
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you have to write a reason and a reasonable[br]reason.
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Not just because "We want to!"
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So in the first part
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I will introduce you
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to the whole thing
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and we talk about bit... about the problem
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which we want to tackle
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with this kind of technique.
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I will mostly present only diagrams
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not actual hardware blocks or relays.
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So you get the basic concept.
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So when we do astronomy
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we do two types of things.
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We either do imaging,
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which is: We maybe produce a nice image
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of a star - so that's the blop over there -
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or we take this image,
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maybe this little blop over there,
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and make it into a spectrum,
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so disperse the light,
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and then we look at the differential intensity
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between the diverse colors
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or are there maybe
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- for example you see black lines in there -
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absorption bands and so on.
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To do such a thing you need a spectrograph
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and in a spectrograph
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there is a thing called an entrance slit.
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So this slit you have to
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put over your objects,
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so you don't get light from left or right next to the object
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to what you want to observe or analyse
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so that you only get light from where you[br]wanted.
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The thing is now
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this slit can not be made
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arbitrarily wide or small,
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because the width of the slit directly
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determines what kind of resolution
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you have in such a spectrometer.
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as it's called. This is a quantity
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Which needs to be above a certain value
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when you want to do certain kinds of analyses.
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So it has fixed width.
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So now if we look at an image produced
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of one of the most capable telescopes
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on this planet
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and we put a representation for this slit
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over the star
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- okay now its white, let's make this black -
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then you see if you want to go
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for that star over there,
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you do have a problem already.
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As said, you can't make this slit wider,
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but the star is actually larger than the slit,
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meaning that you lose light.
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"Well you lose some light...." No!
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If you want to quantitative measurements
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you want to have all the lights
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and all the pixels.
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So you can't get rid of them
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and just throwing something away.
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So, but our image is looking like that.
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It's maybe nice, so but can we do better?
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Yes, we can!
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And this is what we can achieve with
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adaptive optics.
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This is an image that has been produce
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with adaptive optics with a
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LASER AO assisted system.
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And if I flip back and forth you see
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there is a difference!
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All right! So why is that?
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Why don't we get this ideal images?
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The reason is because there is the atmosphere.
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The atmosphere is great for breathing.
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It's not that great for astronomy.
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So if you have a star up there somewhere
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in outer space
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- can be very far away - so the photon
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have travelled for 11 Billion years
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and now they finally hit the atmosphere
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and then something happens
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which you do not want.
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Okay, first they travel freely.
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There is a nice planar wavefront.
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So it's not disturbed by anything,
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maybe something but that's not the
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scope of this evening. It's planar, it's nice!
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And if you actually have a satellite,
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it's very cool.
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Because then you can directly record this
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undisturbed light.
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If you have something on the ground,
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well, you do get a problem,
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because the atmosphere introduces turbulence,
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because, well, the air wobbles a bit.
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There are stream coming from all directions.
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There are temperature gradients in there.
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And these all work together
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and make from this nice planar wave front
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a crumbled one.
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If you have a perfect image
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which you create
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- This is called "diffraction limit".
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This is just limited by the size
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of your optics.
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So the wider your optics is,
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the nicer your resolution is of your image.
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If you then build a large facility with
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maybe two 8 meter mirrors on the ground,
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well, you only get your seeing limited image.
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Seeing limited. The Seeing is this wobbling
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of the atmosphere as it's called.
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And that's about it.
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You can make it arbitrarily large.
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You won't get a better resolution
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then a backyard telescope
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of having 20cm in diameter.
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So yeah...
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What to do?
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There have been people, of course,
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thinking about this problem longer.
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And the first idea came up in 1953.
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And some guy Palomar Observatory
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in California said: "Well, if we have
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the means of continuously measuring
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the deviation of rays from all parts
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of the mirror and amplifying and feedback
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this information so as to correct locally
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the figure of the mirror
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in response to schlieren pattern,
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we could expect to compensate both
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for the seeing and for the inherent imperfections
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in the optical figure."
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Ehhh... what?
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So if we could somehow get rid of this wobbling
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or conteract that,
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then we could get this perfect
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diffraction limited imaging we get in space
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also on the ground.
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In the 1970s the US military started
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to experiment on that.
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Well, I guess the Russians too,
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but it's not... it's known that the US started
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at Starfire Optical Range.
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In 1982 they build the first AO system,
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adaptive optics system.
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The "Compensated Imaging System" on Hawaii.
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And in the late 80s the first astronomical[br]use,
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adaptive optics system "COME-ON"
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as it was called was installed at the
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Observatoire Haute-Provence
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and at ESO at La Silla.
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That's the European Space Observatory.
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All right so that was:
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Yeah, we get for we found that this
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fussy blob is actually not a fussy blob,
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but two fussy blobs.
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laughter
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Well it's a binary system as I would say
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if this was at an astronomical conference.
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But yeah, you disentangle things
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you could not see before.
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Okay! How does this AO system look like in[br]principle?
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So again we have this star somewhere,
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we've learned already that
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we do have... - actually you see this slight
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schlieren pattern in the air
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for the warm and the exhaust from the...
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Yes, there is a bit flimmering in the background.
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That's seeing. Okay?
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So the image is not as sharp here as
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it comes from the projector.
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Okay, that comes from somewhere
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and then we need a system
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which has three components.
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One is a deformable mirror,
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the other is a wave front sensor
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and the third one is a real time computer.
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We need something to actually measure
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what is going on.
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Then we need to take this measurement
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and extract some information from
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this measurement
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and then we need something
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which can correct this wave front,
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straighten it out so to speak,
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'cause we want to have it straight again.
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So the wave front sensor sends some information
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to the real time computer.
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This some information namely is:
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What is the curvature?
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How does this wiggled thingy look like?
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- The wavefront -
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And that real time computer computes
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then information that goes
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to the deformable mirror
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and that in real time shaped
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in an arbitrary shape
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conteracting that incoming wave front
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and then straightening it out.
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So we do have a light path like this.
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First it goes on the deformable mirror,
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goes on something else,
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which I will come to in a minute,
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and then this wave front sensor.
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And of course this means if you run it
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you do have a control loop,
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meaning measure something here,
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the wavefront,
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you put the information into there feeding
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that into the deformable mirror,
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that deforms somehow,
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modifies this wave front that comes
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from above and then of course
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you want to have a feedback loop:
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Is that what I did enough?
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Do I have to do more?
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And also: Of course in the next second
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or split second this pattern
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will have changed,
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because the atmosphere is dynamic.
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If it wasn't dynamic we don't need
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to do this in real time,
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but we have to do it in real time.
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Real time meaning we have to do this correction
0:11:46.420,0:11:50.080
and calculation and sensing at a rate of
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about 1 kHz, so a 1000 times a second.
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Then we have a scientific instrument
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because actually we do want to see
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what is in there.
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And so this thing in the middle
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is a beam splitter.
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It takes some of the light,
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puts it to the wave front sensor
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not all, because most of it should go into
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the scientific instrument
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and there, as you see here,
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then the wave front is straightened out
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again and then I can focus it
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into my instrument.
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To do actually that
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I have to do...
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- This is the one slide in this talk
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with a Greek symbol -
0:12:26.539,0:12:30.510
You have to this incoming wave front
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which is shown in orange
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and then you do a piecewise linear fit
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which is an approximation
0:12:35.649,0:12:36.690
of the slope.
0:12:36.690,0:12:38.390
Of it actually how it looks like.
0:12:38.390,0:12:43.380
It's put into linear pieces.
0:12:43.380,0:12:46.010
And the size of what is normally
0:12:46.010,0:12:49.320
can be taken als a linear fit
0:12:49.320,0:12:51.860
Piece is roughly 10 - 15 cm
0:12:51.860,0:12:53.600
for good observation sites
0:12:53.600,0:12:55.290
while this thingy here
0:12:55.290,0:12:57.649
so this is the primary mirror of the telescope
0:12:57.649,0:12:58.860
which collects all the light
0:12:58.860,0:13:01.310
that comes from outer space
0:13:01.310,0:13:04.339
is usually for the big telescopes
0:13:04.339,0:13:06.990
at this point 8 to 10 meters
0:13:06.990,0:13:13.730
Okay, but how do we get this slope?
0:13:13.730,0:13:15.980
Now we know that we can approximate it
0:13:15.980,0:13:18.000
in pieces, but how do we get
0:13:18.000,0:13:19.960
the slope?
0:13:19.960,0:13:22.140
Because we need theses slopes of course
0:13:22.140,0:13:25.220
fed into this deformable mirror
0:13:25.220,0:13:25.710
to maybe okay:
0:13:25.710,0:13:27.560
If it comes like this, I go like this
0:13:27.560,0:13:29.620
and it comes in nicely
0:13:29.620,0:13:30.960
or comes out nicely.
0:13:30.960,0:13:33.649
So is where the sensor comes in.
0:13:33.649,0:13:36.290
There are different types of these sensors,
0:13:36.290,0:13:37.470
but the one we are using
0:13:37.470,0:13:40.910
is a so called Shack-Hartmann-Sensor.
0:13:40.910,0:13:43.640
And it looks like this.
0:13:43.640,0:13:45.850
We have... this is the ideal case of course.
0:13:45.850,0:13:48.060
So we have an incoming planar wave front
0:13:48.060,0:13:49.560
- straight on.
0:13:49.560,0:13:51.690
And we do have an array of lenses,
0:13:51.690,0:13:57.020
so it's just 1.. 2.. 3.. 4.. lenses
0:13:57.020,0:14:00.050
and then in an array like 4 by 4.
0:14:00.050,0:14:02.300
And they all focus what is coming in
0:14:02.300,0:14:05.500
into onto a detector and this wave front
0:14:05.500,0:14:07.350
that is coming in is planar
0:14:07.350,0:14:09.220
like this on the left.
0:14:09.220,0:14:11.709
Then you do get a regular spaced grid
0:14:11.709,0:14:15.420
of focus points, in this case 4 times 4
0:14:15.420,0:14:17.630
so 16.
0:14:17.630,0:14:19.430
If now this incoming wave front
0:14:19.430,0:14:24.399
is no planar it looks like this.
0:14:24.399,0:14:26.970
So the focus points do move a bit,
0:14:26.970,0:14:28.670
because, well, it came in like this,
0:14:28.670,0:14:29.959
so the focus is offset.
0:14:29.959,0:14:33.730
I will flip it back and forth again.
0:14:33.730,0:14:36.540
So it's looking like this and you see
0:14:36.540,0:14:39.240
of course you do know what is perfect
0:14:39.240,0:14:43.100
meaning they are[br]at their designated grid points.
0:14:43.100,0:14:47.480
If its imperfect, well, then just measure
0:14:47.480,0:14:50.450
the deviation from their zero position
0:14:50.450,0:14:51.270
so to speak
0:14:51.270,0:14:55.720
and then you do have a proxy for the slope.
0:14:55.720,0:14:57.570
Of course it's a bit more complicated[br]than that.
0:14:57.570,0:15:00.300
There are matrices involved which are not
0:15:00.300,0:15:04.790
necessarily in a square form
0:15:04.790,0:15:05.890
and you have to invert them
0:15:05.890,0:15:10.970
and if you don't... yeah... ...
0:15:10.970,0:15:12.660
There are pretty clever people
0:15:12.660,0:15:15.610
and programmers working on this type of
0:15:15.610,0:15:16.870
problems.
0:15:16.870,0:15:19.030
And this is actual current research.
0:15:19.030,0:15:23.650
This is far from done, this field.
0:15:23.650,0:15:27.520
Okay, so suppose we do have the slopes.
0:15:27.520,0:15:29.430
Then we take a deformable mirror
0:15:29.430,0:15:32.580
and this is the zeros order approximation
0:15:32.580,0:15:33.950
of a deformable mirror.
0:15:33.950,0:15:35.640
Let's say the wave front looks like that,
0:15:35.640,0:15:37.630
well, then take just a mirror which is
0:15:37.630,0:15:39.649
maybe reset a bit in the middle
0:15:39.649,0:15:41.470
the other tipped forward.
0:15:41.470,0:15:43.450
It bounces on this mirror
0:15:43.450,0:15:45.820
and because there is something sticking out there
0:15:45.820,0:15:46.680
and in there
0:15:46.680,0:15:49.430
well if this approaches there goes back
0:15:49.430,0:15:50.790
and in the end the whole thing
0:15:50.790,0:15:54.510
when it has been reflected is planar again.
0:15:54.510,0:15:57.170
Okay, that as said,
0:15:57.170,0:15:58.910
that is the easiest order approximation
0:15:58.910,0:16:01.029
for that. It's a bit more complicated.
0:16:01.029,0:16:03.930
Your incoming wave front doesn't look like that
0:16:03.930,0:16:08.680
It's normally a bit more complex.
0:16:08.680,0:16:10.850
And that means you do have to have
0:16:10.850,0:16:17.170
more wobbling in your deformable mirror.
0:16:17.170,0:16:18.279
You could do this.
0:16:18.279,0:16:21.399
That's in the upper diagram.
0:16:21.399,0:16:22.899
You could do this with a membran
0:16:22.899,0:16:24.200
which is continues
0:16:24.200,0:16:27.730
or maybe it's also in pieces
0:16:27.730,0:16:29.580
and this segments are driven up and down
0:16:29.580,0:16:32.450
or maybe tilted by piezo stages
0:16:32.450,0:16:35.140
that are put underneath.
0:16:35.140,0:16:36.540
Remember they have to do like
0:16:36.540,0:16:38.759
a thousand times a second
0:16:38.759,0:16:40.220
or you could do something like
0:16:40.220,0:16:43.720
you take a two piezo electric wafers
0:16:43.720,0:16:45.399
they have opposite polarizations
0:16:45.399,0:16:47.110
put electrodes inbetween
0:16:47.110,0:16:49.060
and then when you apply a voltage to this blue
0:16:49.060,0:16:51.350
electrodes then you have local bending.
0:16:51.350,0:16:52.950
So the one thing will bend up,
0:16:52.950,0:16:55.990
the other ones will bend in the opposite direction.
0:16:55.990,0:16:58.080
And then you do have changing curvature
0:16:58.080,0:17:00.560
on this whole thing.
0:17:00.560,0:17:04.260
It's not that easy of course in reality,
0:17:04.260,0:17:07.510
because they are not completely independent
0:17:07.510,0:17:09.429
one cell will influence the other
0:17:09.429,0:17:11.519
and yes...
0:17:11.519,0:17:14.320
But this is the basic principle.
0:17:14.320,0:17:18.369
Okay, now you have seen
0:17:18.369,0:17:19.970
there was this beam splitter.
0:17:19.970,0:17:22.150
So most of the thing goes into the
0:17:22.150,0:17:23.099
science instrument
0:17:23.099,0:17:26.270
and some goes to our wave front sensor
0:17:26.270,0:17:27.760
of the light.
0:17:27.760,0:17:30.549
If the object we want to record like
0:17:30.549,0:17:34.670
a galaxy that is 11 Billion lightyears away
0:17:34.670,0:17:36.190
then this galaxy is to faint.
0:17:36.190,0:17:38.860
We can't analyse it's light.
0:17:38.860,0:17:41.140
So what do we do?
0:17:41.140,0:17:43.230
We need maybe a star that is nearby.
0:17:43.230,0:17:45.030
So our galaxy, which we actually do want
0:17:45.030,0:17:47.160
to observe, is the red thingy
0:17:47.160,0:17:49.030
the bright star is the yellow one
0:17:49.030,0:17:50.789
and if there are reasonably close together
0:17:50.789,0:17:52.500
- reasonably close meaning
0:17:52.500,0:17:56.280
about 10-20 arcseconds.
0:17:56.280,0:17:58.350
If you stretch your arm and look at
0:17:58.350,0:18:01.750
your little finger at the finger nail,
0:18:01.750,0:18:06.120
this is about 30 arcminutes.
0:18:06.120,0:18:08.950
1 arcminute has 60 arcseconds so it's
0:18:08.950,0:18:09.900
very close!
0:18:09.900,0:18:11.080
It's not like the galaxy is there
0:18:11.080,0:18:13.500
and the star is there. No!
0:18:13.500,0:18:15.550
It's there!
0:18:15.550,0:18:18.460
Because if you have a large separation
0:18:18.460,0:18:22.140
then they do sense different turbulence.
0:18:22.140,0:18:27.330
Simple as that.
0:18:27.330,0:18:28.530
Now the thing is
0:18:28.530,0:18:31.080
that less than 10% of the objects
0:18:31.080,0:18:31.660
you have on sky
0:18:31.660,0:18:33.110
which you are normally interested
0:18:33.110,0:18:36.390
do have a sufficiently close and bright star
0:18:36.390,0:18:37.160
nearby.
0:18:37.160,0:18:38.230
So what to do?
0:18:38.230,0:18:45.290
And now we come to the lasers.[br]laughter
0:18:45.290,0:18:48.270
Because if don't have your....
0:18:48.270,0:18:49.750
If the don't wanna play nicely
0:18:49.750,0:18:54.750
build your own themepark with yes ... you know.
0:18:54.750,0:18:57.929
So make your own star!
0:18:57.929,0:18:59.610
This is what we do.
0:18:59.610,0:19:02.680
Because if the star is not nearby,
0:19:02.680,0:19:04.799
a sufficiently bright one,
0:19:04.799,0:19:07.830
well, why has it to be sufficiently bright?
0:19:07.830,0:19:09.620
Because if you want to do this computation
0:19:09.620,0:19:12.120
a thousand times a second, well,
0:19:12.120,0:19:19.470
then the time for your CCD[br]when you record this image
0:19:19.470,0:19:23.820
for your wavefront is a thousands of a second.
0:19:23.820,0:19:25.280
And if you don't have enough photons
0:19:25.280,0:19:26.799
in a thousands of a second, well,
0:19:26.799,0:19:29.299
then there is no computation of this offset
0:19:29.299,0:19:31.640
of this little green dots on that grid.
0:19:31.640,0:19:33.490
So you need a lot of photons.
0:19:33.490,0:19:36.549
So let's get enough photons!
0:19:36.549,0:19:37.580
And there are actually two things
0:19:37.580,0:19:38.799
what you can do.
0:19:38.799,0:19:42.480
There is a conveniently placed sodium layer
0:19:42.480,0:19:44.280
in the upper atmosphere.
0:19:44.280,0:19:45.620
laughing
0:19:45.620,0:19:47.530
It's 19 km above ground
0:19:47.530,0:19:49.990
and there is a sodium layer.
0:19:49.990,0:19:52.070
And what you actually can do is
0:19:52.070,0:19:54.870
you can take a laser on ground here,
0:19:54.870,0:19:58.179
and then shot laser which corresponds
0:19:58.179,0:20:02.630
to the energy transition of this sodium atoms
0:20:02.630,0:20:07.610
which is 589.2 nm. It's orange.
0:20:07.610,0:20:09.179
And excited those atoms up there
0:20:09.179,0:20:09.960
in the atmosphere and they will
0:20:09.960,0:20:10.620
start to glow.
0:20:10.620,0:20:12.010
And if you have a focus,
0:20:12.010,0:20:13.250
if you focus it in there,
0:20:13.250,0:20:17.400
and than you have a blob of sodium atoms
0:20:17.400,0:20:19.270
lighting up in the upper atmosphere,
0:20:19.270,0:20:21.669
maybe... what ever some hundred meters long
0:20:21.669,0:20:26.640
and some meters wide[br]as big as your focus is there.
0:20:26.640,0:20:30.440
This can be done with a continuous laser.
0:20:30.440,0:20:31.559
This has been done in the past.
0:20:31.559,0:20:33.750
Yes, of course.
0:20:33.750,0:20:37.100
And actually the first instruments
0:20:37.100,0:20:39.360
were build like that.
0:20:39.360,0:20:40.240
The thing is
0:20:40.240,0:20:42.720
in those days they were very, very expensive.
0:20:42.720,0:20:44.799
There is no sodium laser.
0:20:44.799,0:20:50.260
There are only Di LASERs and they are messy
0:20:50.260,0:20:52.030
and expensive.
0:20:52.030,0:20:55.100
Nowadays we can build this as fibre laser
0:20:55.100,0:20:57.730
but not ten 10 years ago or 15 years ago.
0:20:57.730,0:21:00.070
An other solution is to actually
0:21:00.070,0:21:03.470
use Rayleigh scattering in the atmosphere.
0:21:03.470,0:21:06.220
You use a Nd-YAG LASER
0:21:06.220,0:21:08.900
which is 532nm. It's green.
0:21:08.900,0:21:10.650
It's easily available, it's cheap
0:21:10.650,0:21:12.540
compared to the other one.
0:21:12.540,0:21:15.860
And then you focus it in the atmosphere.
0:21:15.860,0:21:17.820
The only thing is:
0:21:17.820,0:21:19.770
You will do have backscatter of photons
0:21:19.770,0:21:21.179
all along the way.
0:21:21.179,0:21:22.410
So you have to think about
0:21:22.410,0:21:24.620
how can I only record light from
0:21:24.620,0:21:26.720
a certain height above ground?
0:21:26.720,0:21:28.890
Because otherwise I don't have a spot,
0:21:28.890,0:21:31.210
I have a ...ehhh... a laser beam column
0:21:31.210,0:21:33.120
somewhere there.
0:21:33.120,0:21:34.400
Okay!
0:21:34.400,0:21:35.990
How do this things look like?
0:21:35.990,0:21:37.960
Can we dim these lights actually a bit?
0:21:37.960,0:21:40.000
Or is it only an off switch?
0:21:40.000,0:21:45.169
Can you check on this? Let's check on there...
0:21:45.169,0:21:49.040
Just push the button... come on...
0:21:49.040,0:21:54.780
No? No. No!
0:21:54.780,0:21:57.800
laughing
0:21:57.800,0:22:06.380
Nooo!
0:22:06.380,0:22:07.700
It's still on here...
0:22:07.700,0:22:12.530
gasp
0:22:12.530,0:22:16.540
All right, it's looking like this.
0:22:16.540,0:22:19.380
Who has been at the camp?
0:22:19.380,0:22:21.150
There was an astronomy talk at the camp
0:22:21.150,0:22:24.910
from Liz.
0:22:24.910,0:22:27.890
Actually if this talk had been tomorrow
0:22:27.890,0:22:29.429
we would had have a live conference
0:22:29.429,0:22:31.720
to that side because Liz is right now here
0:22:31.720,0:22:35.050
and she send me that picture
0:22:35.050,0:22:36.070
just some hours ago.
0:22:36.070,0:22:38.520
That is how the just do things on
0:22:38.520,0:22:41.059
Paranal in Chile.
0:22:41.059,0:22:42.309
The thing I will talk about
0:22:42.309,0:22:44.900
is the green one to the right.
0:22:44.900,0:22:49.640
That's the thing I have been involved with.
0:22:49.640,0:22:52.600
Yea, let's look into that.
0:22:52.600,0:22:55.980
So if you shoot the laser into the atmosphere
0:22:55.980,0:22:57.490
of course you do have problem.
0:22:57.490,0:22:58.860
The star is very far away,
0:22:58.860,0:23:00.790
it's infinitely far away.
0:23:00.790,0:23:01.960
And the light that comes down
0:23:01.960,0:23:05.100
is in a cylinder.
0:23:05.100,0:23:08.660
And if you shoot a laser up, it's a cone.
0:23:08.660,0:23:10.940
So you only probe the green region.
0:23:10.940,0:23:15.580
The unsampled volume of turbulence[br]is to the side.
0:23:15.580,0:23:18.650
That is a problem with our laser AO.
0:23:18.650,0:23:26.200
An other problem we face is this one.
0:23:26.200,0:23:30.140
When we take a star to measure the wave front
0:23:30.140,0:23:33.380
then it passes only once through the atmosphere.
0:23:33.380,0:23:35.530
The laser beam goes up and down.
0:23:35.530,0:23:36.630
And so there is a component
0:23:36.630,0:23:37.760
called tip tilt component
0:23:37.760,0:23:40.870
which is actually just the thing moving around
0:23:40.870,0:23:43.799
It's not just the phase
0:23:43.799,0:23:45.929
that gets disturbance introduced
0:23:45.929,0:23:48.600
in the wave front but this moving around.
0:23:48.600,0:23:54.630
So not the bright and more[br]or less bright twinkling
0:23:54.630,0:23:56.539
little star thingy,
0:23:56.539,0:23:58.289
but the moving around.
0:23:58.289,0:24:00.400
And that can not be sensed[br]with a laser guild star.
0:24:00.400,0:24:02.549
So when ever we do laser AO
0:24:02.549,0:24:04.570
We do need an other star
0:24:04.570,0:24:05.600
to get this component.
0:24:05.600,0:24:08.080
But this star can be a bit further away,
0:24:08.080,0:24:11.669
like an arcminute or 2 arcminutes or so.
0:24:11.669,0:24:17.150
So it's that... is wide. There are enough.
0:24:17.150,0:24:18.490
And then we should think about
0:24:18.490,0:24:20.220
actually what we have to correct and so
0:24:20.220,0:24:23.789
we should make a profile of the turbulence
0:24:23.789,0:24:25.100
above ground.
0:24:25.100,0:24:27.059
And this is how it looks like.
0:24:27.059,0:24:29.390
And for example for the side
0:24:29.390,0:24:32.370
where we are there in Arizona
0:24:32.370,0:24:34.450
we see that most of the turbulence
0:24:34.450,0:24:37.400
is actually just above the ground.
0:24:37.400,0:24:39.360
So we maybe should care mostly
0:24:39.360,0:24:41.220
about the ground layer.
0:24:41.220,0:24:44.559
It's not so much about the high altitude things.
0:24:44.559,0:24:47.230
So and then what we do is:
0:24:47.230,0:24:48.580
Well we want to sample
0:24:48.580,0:24:50.660
the ground stuff nicely
0:24:50.660,0:24:54.679
so we don't take one but 3 lasers.
0:24:54.679,0:24:58.039
So to fill this area nicely.
0:24:58.039,0:25:00.210
And yes, of course, we can also combine this
0:25:00.210,0:25:03.410
and this looks like that.
0:25:03.410,0:25:05.630
This combination we will not talk about today.
0:25:05.630,0:25:09.809
We will only talk about that.
0:25:09.809,0:25:11.080
This is how it looks like.
0:25:11.080,0:25:13.110
So this is our telescope, the primary mirror
0:25:13.110,0:25:16.590
which receives the light from outer space
0:25:16.590,0:25:19.460
it then deflects on the secondary, tertiary
0:25:19.460,0:25:20.600
and than somewhere here.
0:25:20.600,0:25:22.610
But first we need to have to shoot the laser up.
0:25:22.610,0:25:25.539
And it's launched from a laser box
0:25:25.539,0:25:28.940
onto a mirror behind that secondary mirror
0:25:28.940,0:25:30.530
over there into the atmosphere
0:25:30.530,0:25:33.400
and after 40 microseconds it reaches
0:25:33.400,0:25:36.200
an altitude of 12 km.
0:25:36.200,0:25:37.620
And then of course it comes back.
0:25:37.620,0:25:40.220
After 80 microseconds it's here
0:25:40.220,0:25:41.419
in our detector again.
0:25:41.419,0:25:43.730
So the star then lights up,
0:25:43.730,0:25:46.050
has this cone, get's focused there, focus,
0:25:46.050,0:25:48.460
reflected to here
0:25:48.460,0:25:53.820
and we do have our signal[br]in our detector after 80 ms
0:25:53.820,0:25:55.429
and as said, because of course
0:25:55.429,0:25:59.070
the laser has scattering all along its path,
0:25:59.070,0:26:03.350
you want to gate this information to 12 km
0:26:03.350,0:26:05.539
and well then you just -just- look at
0:26:05.539,0:26:06.880
when your laser pulse started
0:26:06.880,0:26:09.419
wait. wait. wait. wait. wait.
0:26:09.419,0:26:11.500
open the shutter for the detector
0:26:11.500,0:26:14.980
for short time after 80ms,
0:26:14.980,0:26:16.350
close it again and then analyse
0:26:16.350,0:26:18.699
and read out what you just did.
0:26:18.699,0:26:19.960
Easy, huh?
0:26:19.960,0:26:21.520
So we are done.
0:26:21.520,0:26:23.390
Thank you for coming to my talk
0:26:23.390,0:26:26.400
and now go out and build your own lasers
0:26:26.400,0:26:28.799
with... to...
0:26:28.799,0:26:30.980
laughing
0:26:30.980,0:26:34.309
Now we are going to look at this thing
0:26:34.309,0:26:37.370
which is actually build and which works.
0:26:37.370,0:26:39.650
So this is called ARGOS.
0:26:39.650,0:26:41.250
It's a ground layer AO system.
0:26:41.250,0:26:42.570
That's what we want to build.
0:26:42.570,0:26:44.210
It has wide field corrections.
0:26:44.210,0:26:46.110
That means you can not correct
0:26:46.110,0:26:49.559
just a tiny patch on sky but for for astronomical use
0:26:49.559,0:26:52.190
a huge area, meaning it's not just
0:26:52.190,0:26:54.070
a circle of 10 arcseconds but
0:26:54.070,0:26:56.850
this thing can correct 4 by 4 arcminutes
0:26:56.850,0:26:58.230
which is huge,
0:26:58.230,0:27:01.559
so all the objects that are in there.
0:27:01.559,0:27:03.669
We have a multi-laser constellation.
0:27:03.669,0:27:05.140
We have seen that why we need this,
0:27:05.140,0:27:05.850
because we want to fill
0:27:05.850,0:27:06.940
the complete ground layer.
0:27:06.940,0:27:10.289
So we have 3 laser guild stars per eye.
0:27:10.289,0:27:11.480
Why per eye?
0:27:11.480,0:27:14.070
This will be clear in minute.
0:27:14.070,0:27:17.419
And we use high power pulse green lasers.
0:27:17.419,0:27:20.710
And this deformable mirror is actually
0:27:20.710,0:27:22.970
build in the telescope system already.
0:27:22.970,0:27:25.299
The secondary mirror is the deformable mirror
0:27:25.299,0:27:26.960
which is very convenient,
0:27:26.960,0:27:29.320
because then all the instruments,
0:27:29.320,0:27:31.020
that sit on the telescope can benefit from
0:27:31.020,0:27:33.980
this system.
0:27:33.980,0:27:36.270
It's installed at this telescope.
0:27:36.270,0:27:38.240
Look's pretty odd. Yes, I admit that.
0:27:38.240,0:27:39.780
That's the Large Binocular Telescope.
0:27:39.780,0:27:41.850
It's two telescopes on one mount.
0:27:41.850,0:27:44.299
One primary, two primaries.
0:27:44.299,0:27:47.570
It's roughly 23 by 25 by 12 meters.
0:27:47.570,0:27:50.789
It sits on Mont Graham in Arizona.
0:27:50.789,0:27:52.470
And it has an adaptive secondary mirror
0:27:52.470,0:27:58.159
which is this violette coloured thingy
0:27:58.159,0:28:00.630
up there in the middle on top.
0:28:00.630,0:28:04.760
This is how it looks like.
0:28:04.760,0:28:05.720
This is the control room
0:28:05.720,0:28:06.800
where you sit.
0:28:06.800,0:28:09.470
This stays fixed.
0:28:09.470,0:28:11.890
All this shiny part rotates.
0:28:11.890,0:28:12.860
That's the actual telescope,
0:28:12.860,0:28:14.500
the red thing that moves up and down.
0:28:14.500,0:28:17.169
So the whole building rotates and it moves
0:28:17.169,0:28:19.210
up and down.
0:28:19.210,0:28:27.419
It's from ceiling... the ceiling is at level[br]11.
0:28:27.419,0:28:30.990
So when you actually sit there,
0:28:30.990,0:28:34.779
you can watch around a bit
0:28:34.779,0:28:39.960
... this is outside... it's winter... yuh!...[br]let's see...
0:28:39.960,0:28:41.940
There is a ladder...
0:28:41.940,0:28:46.070
Yes, this thing is huge...eh.. nice.. cool
0:28:46.070,0:28:47.960
Okay, that's what it's looks like
0:28:47.960,0:28:53.740
when you are actually there.
0:28:53.740,0:28:56.870
Okay, our system layout is like this.
0:28:56.870,0:28:59.789
We have this adaptive secondary mirror
0:28:59.789,0:29:02.820
which is the deformable mirror.
0:29:02.820,0:29:05.580
We have the primary, tertiary.
0:29:05.580,0:29:06.900
That is clear already.
0:29:06.900,0:29:11.520
So we have a laser box.
0:29:11.520,0:29:15.240
The green things is the lasers themselfs.
0:29:15.240,0:29:16.299
So that's how it looks like.
0:29:16.299,0:29:18.179
We produce some laser beams.
0:29:18.179,0:29:19.970
We have steering mirrors in there
0:29:19.970,0:29:22.190
to get them into the right pattern on sky
0:29:22.190,0:29:22.980
of course.
0:29:22.980,0:29:24.330
We do have control cameras,
0:29:24.330,0:29:25.870
if : Is the focus right?
0:29:25.870,0:29:27.059
Is the position right?
0:29:27.059,0:29:28.280
This is one control loop
0:29:28.280,0:29:30.039
another control loop, another control loop
0:29:30.039,0:29:31.590
an other control loop.
0:29:31.590,0:29:33.140
The black thing is the shutter.
0:29:33.140,0:29:35.030
Because we have to close this whole thing,
0:29:35.030,0:29:36.870
when aircrafts are overhead,
0:29:36.870,0:29:38.500
when satellites are overhead.
0:29:38.500,0:29:40.120
So if you want to use this system,
0:29:40.120,0:29:43.100
you have to, 6 weeks in advance, you have to
0:29:43.100,0:29:45.809
put out your list of observable targets
0:29:45.809,0:29:47.230
to some military agency.
0:29:47.230,0:29:49.309
And they will tell you: Okay! Not Okay!
0:29:49.309,0:29:51.840
Okay! Not Okay! Not Okay! Not Okay! Okay!
0:29:51.840,0:29:54.600
Not Okay, meaning something is passing overhead.
0:29:54.600,0:29:56.710
Hmm... what could this be?
0:29:56.710,0:30:03.460
laughing
0:30:03.460,0:30:04.950
Of course, at some point the lasers
0:30:04.950,0:30:07.360
come down again in this cone shape.
0:30:07.360,0:30:11.039
They will reach the primary mirror
0:30:11.039,0:30:14.110
and ultimately it will end up
0:30:14.110,0:30:15.210
in the wave front sensor
0:30:15.210,0:30:18.270
which is much more complex than just this box.
0:30:18.270,0:30:21.929
I showed you before.
0:30:21.929,0:30:23.220
So there are aquisition cameras
0:30:23.220,0:30:25.409
which detect are we at the right spot.
0:30:25.409,0:30:27.990
Do the spots get onto the detector
0:30:27.990,0:30:29.789
in a nice fashion.
0:30:29.789,0:30:31.659
We do have to do this gating, remember?
0:30:31.659,0:30:33.020
We have to open this shutter
0:30:33.020,0:30:36.570
for the CCD when we want to record the light.
0:30:36.570,0:30:39.659
This tiny fraction after 80ms.
0:30:39.659,0:30:43.510
After the laser pulse has been launched.
0:30:43.510,0:30:44.250
It's done in here.
0:30:44.250,0:30:45.179
These are Pockel Cells.
0:30:45.179,0:30:49.320
So its an electro optical effect.
0:30:49.320,0:30:53.980
And then there is also something
0:30:53.980,0:30:55.940
in addition because I said
0:30:55.940,0:30:58.549
we can't do without the tip tilt
0:30:58.549,0:31:00.049
and there is another unit in here
0:31:00.049,0:31:03.059
that sits right in front of the science instrument
0:31:03.059,0:31:04.799
that detects this tip tilt star,
0:31:04.799,0:31:08.140
this additional star.
0:31:08.140,0:31:11.020
So you have the laser wave front light,
0:31:11.020,0:31:13.970
the green one, you do have this tip tilt light,
0:31:13.970,0:31:15.049
the blue one,
0:31:15.049,0:31:17.080
and you do have the actual science light
0:31:17.080,0:31:20.250
from the object you want to observe on sky.
0:31:20.250,0:31:22.799
That goes directly into this scientific instrument
0:31:22.799,0:31:25.250
in the end.
0:31:25.250,0:31:28.020
And then you have a lot of control things.
0:31:28.020,0:31:29.929
Of course, you do need a common clock
0:31:29.929,0:31:33.470
for this synchronization of all this pulses
0:31:33.470,0:31:35.760
and the gating and what not.
0:31:35.760,0:31:37.260
And of course you need the information
0:31:37.260,0:31:40.260
for the tip tilt component and for the wave[br]front
0:31:40.260,0:31:41.440
into this computer
0:31:41.440,0:31:44.110
which sends then all the slops
0:31:44.110,0:31:45.760
- you remember we have to do this
0:31:45.760,0:31:48.760
linear approximation pieces wise, yes -
0:31:48.760,0:31:49.929
into the secondary mirror
0:31:49.929,0:31:52.880
which than deforms in real time.
0:31:52.880,0:31:57.120
And does this a thousand times a second.
0:31:57.120,0:31:59.470
This is how it looks like.
0:31:59.470,0:32:05.210
So when I am there I am roughly that tall.
0:32:05.210,0:32:08.000
The two black tubes right in the middle,
0:32:08.000,0:32:11.960
those are the two tubes which go up.
0:32:11.960,0:32:14.710
Looks like this.
0:32:14.710,0:32:17.529
So, this is how the components are distributed
0:32:17.529,0:32:21.460
over the telescope... once back.. okay
0:32:21.460,0:32:24.220
primary mirror, primary mirror,
0:32:24.220,0:32:26.390
some instruments in the middle,
0:32:26.390,0:32:28.409
some tertiary mirror,
0:32:28.409,0:32:31.839
the secondaries, the adaptive ones up there.
0:32:31.839,0:32:37.900
Yes, I hate to use this laser pointers.
0:32:37.900,0:32:39.440
laughing
0:32:39.440,0:32:40.690
Because I am always going like this... eee
0:32:40.690,0:32:44.520
(green laser pointer on the slides)
0:32:44.520,0:32:48.610
laughing
0:32:48.610,0:32:52.939
That's my man! laughing
0:32:52.939,0:32:54.650
So okay!
0:32:54.650,0:32:58.440
So we do have the adaptive secondary
0:32:58.440,0:33:00.940
up there and then it goes back on the
0:33:00.940,0:33:02.860
tertiary down there and then it goes over
0:33:02.860,0:33:04.580
into the science instrument,
0:33:04.580,0:33:11.999
all the wave front sensors and what not.
0:33:11.999,0:33:14.879
Again, we do have a laser system.
0:33:14.879,0:33:16.760
We have to place somewhere a launch system
0:33:16.760,0:33:19.700
for the laser, a dichroic to separate
0:33:19.700,0:33:23.480
between the laser light, the tip tilt light[br]and the science light.
0:33:23.480,0:33:25.460
We do have to have a wave front sensor
0:33:25.460,0:33:27.529
to check how the wave front looks like.
0:33:27.529,0:33:29.039
We do have to have this tip tilt control.
0:33:29.039,0:33:29.890
We have calibration source.
0:33:29.890,0:33:31.240
A calibration source would be nice
0:33:31.240,0:33:33.510
to calibrate the system during daytime,
0:33:33.510,0:33:38.260
aircraft detection, yes, satellite avoidance,
0:33:38.260,0:33:41.279
-also an issue here- and a control software.
0:33:41.279,0:33:43.840
There are many people just writing...
0:33:43.840,0:33:45.830
...just haha... writing software for this.
0:33:45.830,0:33:51.350
And this is really hard.
0:33:51.350,0:33:53.179
Some are also on the conference.
0:33:53.179,0:33:54.370
They don't want to be pointed out
0:33:54.370,0:33:56.200
as I learned, but you will find them
0:33:56.200,0:34:01.059
at the conference, if you look at the right places.
0:34:01.059,0:34:05.700
That's where the laser box is located.
0:34:05.700,0:34:09.449
Just next to it is the electronics rack.
0:34:09.449,0:34:10.839
How does this thing look like?
0:34:10.839,0:34:12.730
So that is one of our lasers.
0:34:12.730,0:34:17.839
It's about 20 W. Don't get your finger in there.
0:34:17.839,0:34:19.099
laughing
0:34:19.099,0:34:20.940
It really hurts.
0:34:20.940,0:34:25.329
(Did you try?) No!
0:34:25.329,0:34:30.260
There is a mandatory annual laser training of course.
0:34:30.260,0:34:34.679
Yes, if you want to have something[br]like this at home,
0:34:34.679,0:34:37.280
you do need a huge refrigerator next to it
0:34:37.280,0:34:38.940
just for the cooling of that thing.
0:34:38.940,0:34:41.580
This is nothing you want to have at home.
0:34:41.580,0:34:46.418
Just because it's... that bulky... no..it's[br]not..
0:34:46.418,0:34:47.818
but actually when you do
0:34:47.818,0:34:49.379
this green laser pointer thingy
0:34:49.379,0:34:50.790
then there is always this always this:
0:34:50.790,0:34:52.770
"Don't use this for more than 10 seconds."
0:34:52.770,0:34:54.429
Because why? Because the crystal inside
0:34:54.429,0:34:55.429
heats up.
0:34:55.429,0:34:56.980
And if you can't dissipate that heat
0:34:56.980,0:34:58.770
the crystal at some point breaks
0:34:58.770,0:35:00.710
and then your laser pointer is broken.
0:35:00.710,0:35:02.990
This thing gets continuously cooled.
0:35:02.990,0:35:06.510
So, therefore it's a bit more expensive.
0:35:06.510,0:35:08.960
laughing
0:35:08.960,0:35:10.250
If you than put it up,
0:35:10.250,0:35:12.190
so this is still on the lab table
0:35:12.190,0:35:13.589
when it was integrated and tested
0:35:13.589,0:35:15.530
and than at some point it gets put all
0:35:15.530,0:35:17.820
in a box with all this control mirrors
0:35:17.820,0:35:20.020
and cameras and what not.
0:35:20.020,0:35:22.030
But finally you see in the middle
0:35:22.030,0:35:23.520
on this picture there is
0:35:23.520,0:35:26.010
a focusing lens and then you see
0:35:26.010,0:35:29.300
these 3 tiny little beam coming out of there
0:35:29.300,0:35:32.359
which than expand on sky in size
0:35:32.359,0:35:36.089
of course when they are in 12 km height
0:35:36.089,0:35:38.730
but that's how they come out of it.
0:35:38.730,0:35:41.339
And if you install this in the telescope,
0:35:41.339,0:35:42.869
you actually have to tilt the telescope,
0:35:42.869,0:35:44.280
because otherwise you can't reach it.
0:35:44.280,0:35:48.880
And then you need your climbing gear.
0:35:48.880,0:35:50.520
So once you have produced the lasers,
0:35:50.520,0:35:52.310
you need to propagate them to a through
0:35:52.310,0:35:57.849
a dust tube onto a launch mirror,
0:35:57.849,0:36:00.369
a folding mirror and from there to
0:36:00.369,0:36:02.960
a launch mirror.
0:36:02.960,0:36:06.460
Yes and then it looks like this!
0:36:06.460,0:36:09.730
Okay, so the lasers come from here into that
0:36:09.730,0:36:11.690
and then over to the other side
0:36:11.690,0:36:14.859
over the secondary mirror and then
0:36:14.859,0:36:17.920
being shot right up into space
0:36:17.920,0:36:20.450
like this.
0:36:20.450,0:36:23.950
Okay, so if you want to have that at home,
0:36:23.950,0:36:27.020
.... eh... but I can tell you the whole facility
0:36:27.020,0:36:31.980
does cost less than one fully equipped Eurofighter
0:36:31.980,0:36:44.750
laughing[br]applause
0:36:44.750,0:36:48.470
Thank you for taking the hint.
0:36:48.470,0:36:50.339
Yeah, that's how it looks like.
0:36:50.339,0:36:53.260
It's.... yes it's... laughing ... yeah...
0:36:53.260,0:36:56.620
laughingapplause Okay?
0:36:56.620,0:36:59.960
okay... I have to admit this are a bit longer exposers.
0:36:59.960,0:37:01.420
It's not that bright and green
0:37:01.420,0:37:04.450
when you are actually at the telescope up[br]there.
0:37:04.450,0:37:07.510
But if you have been in the dark long enough
0:37:07.510,0:37:11.460
around ten minutes, then I really becomes bright.
0:37:11.460,0:37:13.640
There is a little telescope that observes,
0:37:13.640,0:37:15.859
where actually the spots are on sky.
0:37:15.859,0:37:17.089
And if we have clear sky,
0:37:17.089,0:37:19.260
then we have this constellation on the right.
0:37:19.260,0:37:21.830
So that is how the lasers come up.
0:37:21.830,0:37:25.330
As I said you do see them all the way up,
0:37:25.330,0:37:26.990
but we are interested in the little dots
0:37:26.990,0:37:27.490
at the end.
0:37:27.490,0:37:28.910
You can barely see them.
0:37:28.910,0:37:30.190
If there are high clouds,
0:37:30.190,0:37:36.080
well than we produce something like this.
0:37:36.080,0:37:39.000
We have the dichroic when the light comes[br]back down
0:37:39.000,0:37:39.930
as said.
0:37:39.930,0:37:42.349
Which separates the science light in red
0:37:42.349,0:37:44.320
and the laser light in green.
0:37:44.320,0:37:46.030
This is how it looks like.
0:37:46.030,0:37:49.890
Actually the dichroic is right in front of[br]Sebatian there
0:37:49.890,0:37:51.930
and from there it gets then reflected
0:37:51.930,0:37:55.220
on a reflector and then up into the
0:37:55.220,0:37:59.310
wave front sensing unit.
0:37:59.310,0:38:03.990
So there is the dichroic, there is the reflector,
0:38:03.990,0:38:06.420
and it goes over in this unit
0:38:06.420,0:38:11.300
which is the wave front sensing unit
0:38:11.300,0:38:13.349
which sits there, at the side.
0:38:13.349,0:38:20.150
That's how it looks, when it gets installed.
0:38:20.150,0:38:22.359
And that is how it looks inside.
0:38:22.359,0:38:24.160
So you have the 3 laser beams coming
0:38:24.160,0:38:26.619
from the side, from the sky, of course.
0:38:26.619,0:38:27.720
You have patrol cameras
0:38:27.720,0:38:30.030
which monitor where are these?
0:38:30.030,0:38:32.570
Are they at the right spot?
0:38:32.570,0:38:36.330
Do we have to steer the lasers a bit?
0:38:36.330,0:38:42.160
Than we have some control for the position
0:38:42.160,0:38:45.760
of the laser spots and the field.
0:38:45.760,0:38:47.310
The Pockel cells are the ones
0:38:47.310,0:38:49.520
that do this opening and closing in front
0:38:49.520,0:38:50.230
of the shutter.
0:38:50.230,0:38:52.089
You can't use a mechanic shutter in front
0:38:52.089,0:38:52.890
of the CCD.
0:38:52.890,0:38:55.280
We have to do this electro optically
0:38:55.280,0:38:59.970
So you have a polarization of the laserbeams.
0:38:59.970,0:39:03.440
And you have a polarizer... a cross polarizer
0:39:03.440,0:39:05.420
and then you just turn the polarisation
0:39:05.420,0:39:06.740
of the crystals.
0:39:06.740,0:39:08.410
It's an electro optical effect
0:39:08.410,0:39:10.700
and then it gets passed through
0:39:10.700,0:39:12.700
or it gets blocked.
0:39:12.700,0:39:15.540
Then you also of course have this lens slit arrays
0:39:15.540,0:39:19.080
in there and then the CCD
0:39:19.080,0:39:21.599
which actually records this dot pattern.
0:39:21.599,0:39:23.470
You remember, this 4 by 4...
0:39:23.470,0:39:25.540
well it's not 4 by 4 in our case we do
0:39:25.540,0:39:28.660
have a bit more resolution.
0:39:28.660,0:39:32.339
The sensory looks like this.
0:39:32.339,0:39:35.589
This is actually a custom build CCD.
0:39:35.589,0:39:37.170
Very special.
0:39:37.170,0:39:38.599
The imaging area is in the middle
0:39:38.599,0:39:40.990
and when you read out the thing,
0:39:40.990,0:39:43.250
you split the image in half,
0:39:43.250,0:39:44.720
you transfer it to the sides
0:39:44.720,0:39:46.960
to the frame store area and than read it out.
0:39:46.960,0:39:49.210
'Cause read out is slow, transfer is fast.
0:39:49.210,0:39:51.380
And you have to do this a thousand times
0:39:51.380,0:39:54.190
a second at very low read out noise,
0:39:54.190,0:39:58.560
which is only 4 electron read out noise.
0:39:58.560,0:40:01.109
For the experts here in the audience,
0:40:01.109,0:40:05.030
this is very good.
0:40:05.030,0:40:08.280
It's not many pixels but it's more than enough for us.
0:40:08.280,0:40:09.730
So how does this look like?
0:40:09.730,0:40:11.030
It looks like that!
0:40:11.030,0:40:13.380
So there you have your pattern again,
0:40:13.380,0:40:15.130
regularly spaces pattern of course
0:40:15.130,0:40:19.310
from 3 laser guild stars you get 3 patterns
0:40:19.310,0:40:21.900
and then you analyse, well, the position,
0:40:21.900,0:40:24.230
the relative position, the absolute position
0:40:24.230,0:40:26.490
of those stars on their grid,
0:40:26.490,0:40:29.530
and somehow compute this slopes
0:40:29.530,0:40:33.070
from there feed them back, compute then
0:40:33.070,0:40:35.530
actually electrical information from them
0:40:35.530,0:40:37.450
which you can than feed into your
0:40:37.450,0:40:39.240
deformable mirror again
0:40:39.240,0:40:42.950
which sits on top of the telescope
0:40:42.950,0:40:47.180
and then hopefully everything works.
0:40:47.180,0:40:49.780
This you can digest at home.[br]laughing
0:40:49.780,0:40:52.220
It's in the stream now so it will be
0:40:52.220,0:40:54.329
saved for all eternity
0:40:54.329,0:40:55.240
and all the aliens
0:40:55.240,0:40:57.940
which record all the electromagnetic field
0:40:57.940,0:41:00.790
from Bielefeld... (mumbling)
0:41:00.790,0:41:02.050
laughing
0:41:02.050,0:41:05.579
Anyway, so, just in short.
0:41:05.579,0:41:08.550
There is down in green there is this thing
0:41:08.550,0:41:12.140
that goes up from the lasers through
0:41:12.140,0:41:14.660
some steering mirrors.
0:41:14.660,0:41:19.710
We have diagnostics, then we got to focus
0:41:19.710,0:41:21.530
check launch mirror one and launch mirror two
0:41:21.530,0:41:24.579
onto sky and then we go back
0:41:24.579,0:41:27.000
up there N1 is the primary mirror.
0:41:27.000,0:41:29.099
And then we go through this whole chain
0:41:29.099,0:41:31.740
and there are various control loops
0:41:31.740,0:41:35.109
sitting in there.
0:41:35.109,0:41:37.070
And all this things have to talk together
0:41:37.070,0:41:40.720
on very high rates.
0:41:40.720,0:41:44.579
Sometimes you see 1 kHz other things are a bit slower.
0:41:44.579,0:41:50.030
This all needs highly sophisticated control software.
0:41:50.030,0:41:51.950
And the programmers can be real proud
0:41:51.950,0:41:54.050
of what they did in the past
0:41:54.050,0:41:56.990
with all this control loops.
0:41:56.990,0:42:00.200
The tip tilt is very... much much much easier,
0:42:00.200,0:42:00.829
because all the...
0:42:00.829,0:42:01.960
you remember this tip tilt
0:42:01.960,0:42:03.400
so this all is moving around.
0:42:03.400,0:42:06.030
So you have 4 quadrants at a little cell
0:42:06.030,0:42:08.390
and it moves to somewhere up, down,
0:42:08.390,0:42:09.060
left, right.
0:42:09.060,0:42:10.760
You can easily detect that.
0:42:10.760,0:42:14.280
That is feed into an array
0:42:14.280,0:42:17.470
of 4 Avalanche Photon Diodes
0:42:17.470,0:42:20.020
to actually record this and for that
0:42:20.020,0:42:22.119
we don't need many photons.
0:42:22.119,0:42:24.180
So this tip tilt star can comparably...
0:42:24.180,0:42:28.130
be comparably dim.
0:42:28.130,0:42:30.680
The calibration unit for the daytime calibration
0:42:30.680,0:42:32.130
can be put into the beam,
0:42:32.130,0:42:34.150
so this arms can swing over,
0:42:34.150,0:42:35.750
over the primary mirror and then we can
0:42:35.750,0:42:40.910
inject artificial stars via a hologram
0:42:40.910,0:42:42.890
into the whole unit during daytime
0:42:42.890,0:42:44.510
and calibrate this whole thing.
0:42:44.510,0:42:48.560
And than yes, we are back here.
0:42:48.560,0:42:52.210
This is how we look like.
0:42:52.210,0:42:57.460
Maybe concentrate on this two areas first.
0:42:57.460,0:43:00.750
I will flip back an forth many times.
0:43:00.750,0:43:02.260
But, yeah, what is this?
0:43:02.260,0:43:04.400
Are this two stars which are just fuzzy
0:43:04.400,0:43:05.700
and dim?
0:43:05.700,0:43:07.510
Or is this an extended object?
0:43:07.510,0:43:09.480
The upper one may be a galaxy because it's
0:43:09.480,0:43:11.030
elongated.
0:43:11.030,0:43:13.970
Okay, concentrate on that.
0:43:13.970,0:43:24.450
Well, it actually just a bunch of stars.
0:43:24.450,0:43:26.099
And this is over a huge field.
0:43:26.099,0:43:28.170
So the correction is not just in the middle
0:43:28.170,0:43:30.570
but you can see also at the very edges
0:43:30.570,0:43:33.040
of this image, we do see this improvement
0:43:33.040,0:43:34.540
in image quality.
0:43:34.540,0:43:39.480
Of course you can have the diagram, if you want.
0:43:39.480,0:43:43.190
So the blue line is without the thing beam activated,
0:43:43.190,0:43:44.300
open loop,
0:43:44.300,0:43:46.349
and if we close the control loop, to do
0:43:46.349,0:43:49.040
this measurement and correction in real time
0:43:49.040,0:43:53.589
we do squeeze all the energy into a few pixels
0:43:53.589,0:43:54.800
which of course also means
0:43:54.800,0:43:57.730
our signal to noise level in a single pixel
0:43:57.730,0:43:59.140
goes up tremendously.
0:43:59.140,0:44:00.460
Meaning you can decrease
0:44:00.460,0:44:03.320
your exposer time.
0:44:03.320,0:44:06.200
Which is important if you want to observe[br]galaxies
0:44:06.200,0:44:09.349
at this telescopes
0:44:09.349,0:44:12.480
it's 200 Dollars a minute.
0:44:12.480,0:44:16.460
laughing
0:44:16.460,0:44:18.370
It's not cheap.
0:44:18.370,0:44:23.920
Okay, good so... the thing...
0:44:23.920,0:44:27.520
just last week there was[br]another commissioning run
0:44:27.520,0:44:30.339
testing commissioning run for this system.
0:44:30.339,0:44:34.420
And my colleges José Borelli and Lorenzo Busoni
0:44:34.420,0:44:36.450
have done a nice video.
0:44:36.450,0:44:38.810
The music btw. "hallo gamer"
0:44:38.810,0:44:42.599
it's royalty for ears...
0:44:42.599,0:44:46.040
If it was now darker therefore I asked,
0:44:46.040,0:44:47.880
this would come up nicer,
0:44:47.880,0:44:49.060
but let's see!
0:44:49.060,0:44:50.880
There is sound hopefully,
0:44:50.880,0:44:53.260
so the sound guys, let's see!
0:46:40.720,0:47:00.020
applause
0:47:00.020,0:47:02.540
Of course this a longer exposure.
0:47:02.540,0:47:07.089
It's not that starwars like
0:47:07.089,0:47:09.810
I would have loved to use some starwars
0:47:09.810,0:47:13.349
tones along those. But you know, all those rights
0:47:13.349,0:47:16.640
and... what not... yes... anyway!
0:47:16.640,0:47:17.770
That's how it looks like.
0:47:17.770,0:47:22.559
So you have 3 laser beams per eye.
0:47:22.559,0:47:24.910
Remember, we have 2 telescopes on one mount.
0:47:24.910,0:47:26.490
They look roughly in the same direction
0:47:26.490,0:47:28.630
but still...
0:47:28.630,0:47:31.460
So if you observe two telescopes
0:47:31.460,0:47:39.640
at the same time it's only 100 dollars a minute.
0:47:39.640,0:47:44.270
Yea, This is not so much the shiny part
0:47:44.270,0:47:47.130
on the dome itself, but if you actually
0:47:47.130,0:47:49.240
do stand on the mountain during night
0:47:49.240,0:47:50.859
and are a bit dark adapted,
0:47:50.859,0:47:54.800
you see the laser beams like that.
0:47:54.800,0:47:57.230
And don't be fooled!
0:47:57.230,0:47:59.770
If you are at the valley,
0:47:59.770,0:48:02.560
or very far away you hardly see them.
0:48:02.560,0:48:03.829
You don't see them at all.
0:48:03.829,0:48:04.990
You see them there.
0:48:04.990,0:48:08.079
If you are two kilometers off side already,
0:48:08.079,0:48:10.650
it's merely a dim greenish something.
0:48:10.650,0:48:13.390
If you are down in the valley 10 km off,
0:48:13.390,0:48:14.640
you don't see them any more.
0:48:14.640,0:48:17.460
If you take a camera, 5 minutes exposer, yes!
0:48:17.460,0:48:18.919
But otherwise, No!
0:48:18.919,0:48:20.180
There is no such thing as
0:48:20.180,0:48:22.690
"The people in the valley down can see like
0:48:22.690,0:48:29.350
these lasers pew pew every night.".. and no.
0:48:29.350,0:48:37.330
Ok, which gets me to the last part.
0:48:37.330,0:48:40.089
How, do you become
0:48:40.089,0:48:45.949
and how do you work as a laser rocket scientist?
0:48:45.949,0:48:48.099
Yes, I put this in the talk directly,
0:48:48.099,0:48:50.660
because I do get this question in the Q&A, normally,
0:48:50.660,0:48:52.690
when I talk about these things,
0:48:52.690,0:48:53.670
and it's always like:
0:48:53.670,0:48:58.659
"What do I need to do if I want to do this?"
0:48:58.659,0:49:01.520
Maybe you have already an idea about this
0:49:01.520,0:49:05.119
because you have seen[br]how complex this thing is.
0:49:05.119,0:49:12.859
And, there are so many things to do in these[br]kind of projects
0:49:12.859,0:49:16.150
and on various levels, also in the administration,
0:49:16.150,0:49:22.450
also for senior people, new people, maybe[br]master thesis works on that
0:49:22.450,0:49:28.819
or bachelor, or PHD or then as a post-doc.
0:49:28.819,0:49:30.160
It's very complex.
0:49:30.160,0:49:34.150
Yes, and it's not only about just shooting[br]lasers in the end.
0:49:34.150,0:49:39.250
Sometimes it's just about checking the cables
0:49:39.250,0:49:41.020
It needs to be done.
0:49:41.020,0:49:45.690
There is a tremendous amount of electronics[br]and electrics involved.
0:49:45.690,0:49:52.240
There are all the mechanical components in[br]such a system are custom built.
0:49:52.240,0:49:55.579
Either the institutes built it themselves
0:49:55.579,0:49:59.210
or they give it out of house.
0:49:59.210,0:50:01.319
There are these real time computers, for example.
0:50:01.319,0:50:02.829
this is by the way our real time computer
0:50:02.829,0:50:05.880
from micrograde, if you want to look that up.
0:50:05.880,0:50:08.460
it's company. It builds these things.
0:50:08.460,0:50:10.650
They need to be programmed.
0:50:10.650,0:50:13.579
Oh, if actually somebody is here in the audience
0:50:13.579,0:50:15.599
with real hard core experience on
0:50:15.599,0:50:18.750
real time computing, coding and such things,
0:50:18.750,0:50:20.590
do talk to me!
0:50:20.590,0:50:23.540
laughing
0:50:23.540,0:50:26.540
Yeah, this is how our software system looks like.
0:50:26.540,0:50:31.839
A very small part of the GUIs. It's a lot of code
0:50:31.839,0:50:35.010
and a lot of work and a lot of sleepless nights
0:50:35.010,0:50:38.760
in front of these computers[br]and just testing it and testing it
0:50:38.760,0:50:41.829
and then testing some more,[br]and testing even more.
0:50:41.829,0:50:44.859
And, to be involved in these kind of projects,
0:50:44.859,0:50:48.560
you don't need to be a laser physicist,
0:50:48.560,0:50:51.479
because there is no one thing.
0:50:51.479,0:50:54.890
If you want to take 3 messages[br]out of this, it's:
0:50:54.890,0:50:57.060
it's a team effort, there are many tasks,
0:50:57.060,0:51:01.499
and there are many jobs,[br]and you have to pick one.
0:51:01.499,0:51:04.170
Because in this one job you do in these projects
0:51:04.170,0:51:06.500
you have to be very, very, very good.
0:51:06.500,0:51:09.750
Because there are other people that are very,[br]very, very good.
0:51:09.750,0:51:13.650
If you work in these kind of projects, if[br]you meet a new person for the first time
0:51:13.650,0:51:17.359
just assume that he or she knows[br]everything about this
0:51:17.359,0:51:18.940
and you know nothing.
0:51:18.940,0:51:24.130
You will quickly realize if that is true.
0:51:24.130,0:51:26.319
But otherwise, if you assume it[br]the other way round,
0:51:26.319,0:51:28.730
you just make a fool of yourself, okay?
0:51:28.730,0:51:29.849
Don't do that.
0:51:29.849,0:51:34.170
People in science, second most important thing[br]if you really want go into this,
0:51:34.170,0:51:38.740
people in science are just like[br]people outside science
0:51:38.740,0:51:42.429
meaning you will meet nice people[br]and you will meet.....
0:51:42.429,0:51:44.800
laughing
0:51:44.800,0:51:47.480
just like in life.
0:51:47.480,0:51:52.470
It's not that these things are spheres[br]where people are, you know
0:51:52.470,0:51:57.180
floating above the lab surface and nice coloured.
0:51:57.180,0:52:00.819
No, it's hard work.
0:52:00.819,0:52:04.829
And if you actually go into this[br]like study physics
0:52:04.829,0:52:08.640
or maybe if you want to construct this,
0:52:08.640,0:52:10.480
of course all the drawings are done by
0:52:10.480,0:52:13.339
people how have learned this in there studies,
0:52:13.339,0:52:16.810
so "Maschinenbau" what ever...
0:52:16.810,0:52:18.210
Go for that one.
0:52:18.210,0:52:21.079
Building optics needs optics experience.
0:52:21.079,0:52:23.520
If you want to actually build stuff,
0:52:23.520,0:52:26.079
well, there are many people in this institutes
0:52:26.079,0:52:28.099
or universities who work
0:52:28.099,0:52:30.500
in the mechanical fabrication departments
0:52:30.500,0:52:31.609
or electronics departments.
0:52:31.609,0:52:35.460
They just do PCB layouting all the time.
0:52:35.460,0:52:38.369
But this things do need sophisticated electronics
0:52:38.369,0:52:40.140
and this all custom built.
0:52:40.140,0:52:42.160
This is nothing you can buy of the shelf.
0:52:42.160,0:52:45.300
Nothing of it! Almost nothing.
0:52:45.300,0:52:46.500
And this means you might end up
0:52:46.500,0:52:48.819
with something equally cool.
0:52:48.819,0:52:51.099
It's not that you can have this one thing
0:52:51.099,0:52:53.829
and then BAM ten years later you will be
0:52:53.829,0:52:56.829
the laser-rocket scientist. You won't!
0:52:56.829,0:52:58.740
You might become one
0:52:58.740,0:53:01.819
and then even after 10 years,
0:53:01.819,0:53:04.010
you might realize this is not the thing
0:53:04.010,0:53:07.660
you want to do forever.
0:53:07.660,0:53:09.380
So I have to correct
0:53:09.380,0:53:10.900
the introduction in one point:
0:53:10.900,0:53:12.750
I'm no longer working there.
0:53:12.750,0:53:14.819
I recently left.
0:53:14.819,0:53:17.849
I'm now have my own company.
0:53:17.849,0:53:19.270
I'm still involved in these things.
0:53:19.270,0:53:21.710
I do calculations for this kinds of things,
0:53:21.710,0:53:23.520
but I'm not at an institute any more,
0:53:23.520,0:53:25.900
because I decided for example for me
0:53:25.900,0:53:29.190
that the contract conditions in this type
0:53:29.190,0:53:33.440
of scientific work are not of the type,
0:53:33.440,0:53:38.400
which I want to live with any more.
0:53:38.400,0:53:40.500
Like one year contracts.
0:53:40.500,0:53:49.220
applause
0:53:49.220,0:53:51.760
And so there are many ways[br]of being involved in this
0:53:51.760,0:53:53.970
and don't just... don't just[br]focus on the this!
0:53:53.970,0:53:56.710
Focus on what you really want to do and
0:53:56.710,0:53:59.440
you might end up in this
0:53:59.440,0:54:00.650
and if you don't,
0:54:00.650,0:54:03.563
well you do something equally cool.
0:55:52.879,0:55:56.730
All right! Questions?
0:55:56.730,0:56:04.800
applause
0:56:04.800,0:56:06.839
Herald: Okay, first of all
0:56:06.839,0:56:10.450
thank you for our daily dosis of lasers.
0:56:10.450,0:56:13.730
I have said... Ich hab keine Zeit...
0:56:13.730,0:56:16.589
cause we have really not much time left for Q&A,
0:56:16.589,0:56:19.530
so I'm first asking the signal angel,
0:56:19.530,0:56:21.410
if there are any questions from the internet,
0:56:21.410,0:56:25.880
because... was that a 2? 2! ok.
0:56:25.880,0:56:28.670
because this people can't ask questions afterwards,[br]soo...
0:56:28.670,0:56:31.329
Peter: I'll be all congress and[br]if you want to reach me
0:56:31.329,0:56:35.699
directly 7319 is this telephone.
0:56:35.699,0:56:39.030
Herald: Ok, the signal angel questions.
0:56:39.030,0:56:41.130
Signal A.: Yeah, the first question from the[br]internet was:
0:56:41.130,0:56:43.559
How strong the laser actually is
0:56:43.559,0:56:45.509
or if it could be any danger for something
0:56:45.509,0:56:47.380
in the vicinity?
0:56:47.380,0:56:48.440
Peter: Actually, no!
0:56:48.440,0:56:51.210
So we shoot up around 15 to 20 W
0:56:51.210,0:56:53.290
per laser beam.
0:56:53.290,0:56:55.579
If there was actually a plane flying through
0:56:55.579,0:56:58.410
our laser beam,
0:56:58.410,0:57:01.380
then nothing happens to the pilots.
0:57:01.380,0:57:03.040
They don't get blinded or what not,
0:57:03.040,0:57:06.290
because it's di... the beamsize at that altitude
0:57:06.290,0:57:09.069
is so big already.. they will of course look like:
0:57:09.069,0:57:10.710
"Errr what is this?"
0:57:10.710,0:57:12.720
And that's what we do not want,
0:57:12.720,0:57:14.470
because then they might push some other buttons
0:57:14.470,0:57:16.660
which they are not suppose to push.
0:57:16.660,0:57:17.750
laughing
0:57:17.750,0:57:20.270
If you of course work directly at the system,
0:57:20.270,0:57:21.200
you have to maintain it,
0:57:21.200,0:57:24.140
you open it, you have to align the lasers
0:57:24.140,0:57:27.559
and what not beyond there self aligning capabilities,
0:57:27.559,0:57:29.619
you do have to wear[br]all this protective laser goggles
0:57:29.619,0:57:32.140
and what not, because if you do...
0:57:32.140,0:57:35.359
if you don't you do have instant eye damage.
0:57:35.359,0:57:39.189
It is not... no its instant.
0:57:39.189,0:57:41.400
You might not see it instantly.
0:57:41.400,0:57:45.160
But the instant... it's there instantly, period.
0:57:45.160,0:57:48.290
So really, folks, don't experiment on this
0:57:48.290,0:57:49.589
laser stuff at home,
0:57:49.589,0:57:53.319
if you are not following basic[br]laser safety rules.
0:57:53.319,0:57:56.290
Not prying this things from the DVD burners
0:57:56.290,0:58:00.540
or no blue ray thingys "uuh does it really work?"
0:58:00.540,0:58:02.030
Just, just don't!
0:58:02.030,0:58:05.329
Your eyesight is not worth it. period.
0:58:05.329,0:58:08.080
It's not!
0:58:08.080,0:58:10.849
Herald: Please remember to cover[br]your still working eye!
0:58:10.849,0:58:13.500
Peter: Yeah... only look into the laser[br]beam
0:58:13.500,0:58:16.130
with your remaining eye.
0:58:16.130,0:58:17.489
Herald: The other question?
0:58:17.489,0:58:20.040
Signal A. :And the second question from the internet
0:58:20.040,0:58:21.940
was... It's actually commenting that,
0:58:21.940,0:58:24.230
this was a very cool concept already been used
0:58:24.230,0:58:26.520
and where do you see this going
0:58:26.520,0:58:28.849
in the next 10 years, so what's the outlook
0:58:28.849,0:58:31.820
for observation from the Earth's surface
0:58:31.820,0:58:33.250
in the next 10 years?
0:58:33.250,0:58:34.569
Peter: Oh, of course
0:58:34.569,0:58:36.089
the telescopes will get bigger and bigger.
0:58:36.089,0:58:38.170
The next generation of the telescope is coming up
0:58:38.170,0:58:39.660
in the 2020s.
0:58:39.660,0:58:41.369
The European Extremely Large Telescope
0:58:41.369,0:58:45.200
will be about roughly around[br]40 meters in diameter.
0:58:45.200,0:58:47.220
These are so huge they can't work in
0:58:47.220,0:58:49.250
seeing limited operation any more.
0:58:49.250,0:58:54.030
They do have to have laser AO all the time.
0:58:54.030,0:58:55.609
It will look similar to this.
0:58:55.609,0:58:57.349
So this is in that sense also
0:58:57.349,0:58:58.650
a technology demonstrator.
0:58:58.650,0:59:01.910
There will be a combined thing.
0:59:01.910,0:59:03.850
You may remember this diagram
0:59:03.850,0:59:06.260
with the one sodium laser in the middle
0:59:06.260,0:59:07.740
and the others outside.
0:59:07.740,0:59:09.319
So these combined things.
0:59:09.319,0:59:12.240
And then you can also imagine something,
0:59:12.240,0:59:13.869
that you probe different heights
0:59:13.869,0:59:14.910
in the atmosphere,
0:59:14.910,0:59:18.130
because you do have different turbulence layers
0:59:18.130,0:59:22.480
and all of these then have their own
0:59:22.480,0:59:23.750
deformable mirror.
0:59:23.750,0:59:25.660
So it's a very comp... gets a very complex[br]set,
0:59:25.660,0:59:29.460
a multi conjugate AO as it's called.
0:59:29.460,0:59:30.700
And then there are of course
0:59:30.700,0:59:33.940
new... there is research being done on
0:59:33.940,0:59:36.950
how to detect this wave front
0:59:36.950,0:59:38.089
most efficently.
0:59:38.089,0:59:40.380
And there is a so called thing called
0:59:40.380,0:59:42.410
the pyramid sensor.
0:59:42.410,0:59:44.230
You can look for that, also
0:59:44.230,0:59:46.220
we do have one in our system.
0:59:46.220,0:59:47.730
And this is very efficient.
0:59:47.730,0:59:49.680
So it takes much less photons
0:59:49.680,0:59:52.750
to get to the same signal to noise level.
0:59:52.750,0:59:55.740
This is active research and... well...
0:59:55.740,0:59:58.140
Every major telescope of course now has this.
0:59:58.140,1:00:00.400
And every big telescopes in the future
1:00:00.400,1:00:04.870
will have this all over the place.
1:00:04.870,1:00:09.270
Herald: Okay, we're completely out of time.[br]Again.
1:00:09.270,1:00:10.580
Again, so thank you very much.
1:00:10.580,1:00:12.070
Peter: Thank you!
1:00:12.070,1:00:17.491
applause
1:00:17.491,1:00:22.851
postroll music
1:00:22.851,1:00:29.000
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