*preroll music*
Herald: Our next speaker has studied in Bielefeld,
and he studied... *laughter**clapping*
what he did is: He studied laser physics.
And now he is working at the Max Planck Institute for extraterrestrial physics.
And today he will explain you
how it is possible to use laser light
to enhance distorted images
that were take from the earth
of stars and galaxies and nebulars.
So I want to hear a
really loud and warm applaus
for Peter Buschkamp with
"Shooting lasers into space -
For science"! *applause*
All right! Thank you for the nice introduction
Thank you, for coming here
this evening.
I'm very excited
to speak at the conference.
Finally I find a talk
where I can contribute
after all those years.
I'm not going to talk about Bielefeld.
You might want to hear something about that.
I'm not allowed to tell you... right?
Okay, so today I'm going to talk about
a bit what is in my field
of experties.
If there is one thing
I want to bring across to you
then it is
It's not about a single person
showing this to you this evening.
This is a team effort and a real team effort.
So most of the images are done by
a college of mine Julian Ziegeleder.
And the PI of the project,
so the leader of the project
Sebastian Rabien
has contributed some slides.
And I wouldn't be standing here today
and showing you these images
if it wasn't for a huge team
and many people.
I hope this is reasonably complete,
but I think there were even more.
Many people have tributed most and
long years of there career into such a project.
So this is never about something
which a single person does
and he or she finds something very cool
and then saves the world.
No, it's always a big, big team!
But before we actually see the lasers
then in working, we have of course to clarify
why we do this.
This is not just because we can.
We can! But there is a reason for that,
because if you want to get funding,
you have to write a reason and a reasonable reason.
Not just because "We want to!"
So in the first part
I will introduce you
to the whole thing
and we talk about bit... about the problem
which we want to tackle
with this kind of technique.
I will mostly present only diagrams
not actual hardware blocks or relays.
So you get the basic concept.
So when we do astronomy
we do two types of things.
We either do imaging,
which is: We maybe produce a nice image
of a star - so that's the blop over there -
or we take this image,
maybe this little blop over there,
and make it into a spectrum,
so disperse the light,
and then we look at the differential intensity
between the diverse colors
or are there maybe
- for example you see black lines in there -
absorption bands and so on.
To do such a thing you need a spectrograph
and in a spectrograph
there is a thing called an entrance slit.
So this slit you have to
put over your objects,
so you don't get light from left or right next to the object
to what you want to observe or analyse
so that you only get light from where you wanted.
The thing is now
this slit can not be made
arbitrarily wide or small,
because the width of the slit directly
determines what kind of resolution
you have in such a spectrometer.
as it's called. This is a quantity
Which needs to be above a certain value
when you want to do certain kinds of analyses.
So it has fixed width.
So now if we look at an image produced
of one of the most capable telescopes
on this planet
and we put a representation for this slit
over the star
- okay now its white, let's make this black -
then you see if you want to go
for that star over there,
you do have a problem already.
As said, you can't make this slit wider,
but the star is actually larger than the slit,
meaning that you lose light.
"Well you lose some light...." No!
If you want to quantitative measurements
you want to have all the lights
and all the pixels.
So you can't get rid of them
and just throwing something away.
So, but our image is looking like that.
It's maybe nice, so but can we do better?
Yes, we can!
And this is what we can achieve with
adaptive optics.
This is an image that has been produce
with adaptive optics with a
LASER AO assisted system.
And if I flip back and forth you see
there is a difference!
All right! So why is that?
Why don't we get this ideal images?
The reason is because there is the atmosphere.
The atmosphere is great for breathing.
It's not that great for astronomy.
So if you have a star up there somewhere
in outer space
- can be very far away - so the photon
have travelled for 11 Billion years
and now they finally hit the atmosphere
and then something happens
which you do not want.
Okay, first they travel freely.
There is a nice planar wavefront.
So it's not disturbed by anything,
maybe something but that's not the
scope of this evening. It's planar, it's nice!
And if you actually have a satellite,
it's very cool.
Because then you can directly record this
undisturbed light.
If you have something on the ground,
well, you do get a problem,
because the atmosphere introduces turbulence,
because, well, the air wobbles a bit.
There are stream coming from all directions.
There are temperature gradients in there.
And these all work together
and make from this nice planar wave front
a crumbled one.
If you have a perfect image
which you create
- This is called "diffraction limit".
This is just limited by the size
of your optics.
So the wider your optics is,
the nicer your resolution is of your image.
If you then build a large facility with
maybe two 8 meter mirrors on the ground,
well, you only get your seeing limited image.
Seeing limited. The Seeing is this wobbling
of the atmosphere as it's called.
And that's about it.
You can make it arbitrarily large.
You won't get a better resolution
then a backyard telescope
of having 20cm in diameter.
So yeah...
What to do?
There have been people, of course,
thinking about this problem longer.
And the first idea came up in 1953.
And some guy Palomar Observatory
in California said: "Well, if we have
the means of continuously measuring
the deviation of rays from all parts
of the mirror and amplifying and feedback
this information so as to correct locally
the figure of the mirror
in response to schlieren pattern,
we could expect to compensate both
for the seeing and for the inherent imperfections
in the optical figure."
Ehhh... what?
So if we could somehow get rid of this wobbling
or conteract that,
then we could get this perfect
diffraction limited imaging we get in space
also on the ground.
In the 1970s the US military started
to experiment on that.
Well, I guess the Russians too,
but it's not... it's known that the US started
at Starfire Optical Range.
In 1982 they build the first AO system,
adaptive optics system.
The "Compensated Imaging System" on Hawaii.
And in the late 80s the first astronomical use,
adaptive optics system "COME-ON"
as it was called was installed at the
Observatoire Haute-Provence
and at ESO at La Silla.
That's the European Space Observatory.
All right so that was:
Yeah, we get for we found that this
fussy blob is actually not a fussy blob,
but two fussy blobs.
*laughter*
Well it's a binary system as I would say
if this was at an astronomical conference.
But yeah, you disentangle things
you could not see before.
Okay! How does this AO system look like in principle?
So again we have this star somewhere,
we've learned already that
we do have... - actually you see this slight
schlieren pattern in the air
for the warm and the exhaust from the...
Yes, there is a bit flimmering in the background.
That's seeing. Okay?
So the image is not as sharp here as
it comes from the projector.
Okay, that comes from somewhere
and then we need a system
which has three components.
One is a deformable mirror,
the other is a wave front sensor
and the third one is a real time computer.
We need something to actually measure
what is going on.
Then we need to take this measurement
and extract some information from
this measurement
and then we need something
which can correct this wave front,
straighten it out so to speak,
'cause we want to have it straight again.
So the wave front sensor sends some information
to the real time computer.
This some information namely is:
What is the curvature?
How does this wiggled thingy look like?
- The wavefront -
And that real time computer computes
then information that goes
to the deformable mirror
and that in real time shaped
in an arbitrary shape
conteracting that incoming wave front
and then straightening it out.
So we do have a light path like this.
First it goes on the deformable mirror,
goes on something else,
which I will come to in a minute,
and then this wave front sensor.
And of course this means if you run it
you do have a control loop,
meaning measure something here,
the wavefront,
you put the information into there feeding
that into the deformable mirror,
that deforms somehow,
modifies this wave front that comes
from above and then of course
you want to have a feedback loop:
Is that what I did enough?
Do I have to do more?
And also: Of course in the next second
or split second this pattern
will have changed,
because the atmosphere is dynamic.
If it wasn't dynamic we don't need
to do this in real time,
but we have to do it in real time.
Real time meaning we have to do this correction
and calculation and sensing at a rate of
about 1 kHz, so a 1000 times a second.
Then we have a scientific instrument
because actually we do want to see
what is in there.
And so this thing in the middle
is a beam splitter.
It takes some of the light,
puts it to the wave front sensor
not all, because most of it should go into
the scientific instrument
and there, as you see here,
then the wave front is straightened out
again and then I can focus it
into my instrument.
To do actually that
I have to do...
- This is the one slide in this talk
with a Greek symbol -
You have to this incoming wave front
which is shown in orange
and then you do a piecewise linear fit
which is an approximation
of the slope.
Of it actually how it looks like.
It's put into linear pieces.
And the size of what is normally
can be taken als a linear fit
Piece is roughly 10 - 15 cm
for good observation sites
while this thingy here
so this is the primary mirror of the telescope
which collects all the light
that comes from outer space
is usually for the big telescopes
at this point 8 to 10 meters
Okay, but how do we get this slope?
Now we know that we can approximate it
in pieces, but how do we get
the slope?
Because we need theses slopes of course
fed into this deformable mirror
to maybe okay:
If it comes like this, I go like this
and it comes in nicely
or comes out nicely.
So is where the sensor comes in.
There are different types of these sensors,
but the one we are using
is a so called Shack-Hartmann-Sensor.
And it looks like this.
We have... this is the ideal case of course.
So we have an incoming planar wave front
- straight on.
And we do have an array of lenses,
so it's just 1.. 2.. 3.. 4.. lenses
and then in an array like 4 by 4.
And they all focus what is coming in
into onto a detector and this wave front
that is coming in is planar
like this on the left.
Then you do get a regular spaced grid
of focus points, in this case 4 times 4
so 16.
If now this incoming wave front
is no planar it looks like this.
So the focus points do move a bit,
because, well, it came in like this,
so the focus is offset.
I will flip it back and forth again.
So it's looking like this and you see
of course you do know what is perfect
meaning they are at their designated grid points.
If its imperfect, well, then just measure
the deviation from their zero position
so to speak
and then you do have a proxy for the slope.
Of course it's a bit more complicated than that.
There are matrices involved which are not
necessarily in a square form
and you have to invert them
and if you don't... yeah... ...
There are pretty clever people
and programmers working on this type of
problems.
And this is actual current research.
This is far from done, this field.
Okay, so suppose we do have the slopes.
Then we take a deformable mirror
and this is the zeros order approximation
of a deformable mirror.
Let's say the wave front looks like that,
well, then take just a mirror which is
maybe reset a bit in the middle
the other tipped forward.
It bounces on this mirror
and because there is something sticking out there
and in there
well if this approaches there goes back
and in the end the whole thing
when it has been reflected is planar again.
Okay, that as said,
that is the easiest order approximation
for that. It's a bit more complicated.
Your incoming wave front doesn't look like that
It's normally a bit more complex.
And that means you do have to have
more wobbling in your deformable mirror.
You could do this.
That's in the upper diagram.
You could do this with a membran
which is continues
or maybe it's also in pieces
and this segments are driven up and down
or maybe tilted by piezo stages
that are put underneath.
Remember they have to do like
a thousand times a second
or you could do something like
you take a two piezo electric wafers
they have opposite polarizations
put electrodes inbetween
and then when you apply a voltage to this blue
electrodes then you have local bending.
So the one thing will bend up,
the other ones will bend in the opposite direction.
And then you do have changing curvature
on this whole thing.
It's not that easy of course in reality,
because they are not completely independent
one cell will influence the other
and yes...
But this is the basic principle.
Okay, now you have seen
there was this beam splitter.
So most of the thing goes into the
science instrument
and some goes to our wave front sensor
of the light.
If the object we want to record like
a galaxy that is 11 Billion lightyears away
then this galaxy is to faint.
We can't analyse it's light.
So what do we do?
We need maybe a star that is nearby.
So our galaxy, which we actually do want
to observe, is the red thingy
the bright star is the yellow one
and if there are reasonably close together
- reasonably close meaning
about 10-20 arcseconds.
If you stretch your arm and look at
your little finger at the finger nail,
this is about 30 arcminutes.
1 arcminute has 60 arcseconds so it's
very close!
It's not like the galaxy is there
and the star is there. No!
It's there!
Because if you have a large separation
then they do sense different turbulence.
Simple as that.
Now the thing is
that less than 10% of the objects
you have on sky
which you are normally interested
do have a sufficiently close and bright star
nearby.
So what to do?
And now we come to the lasers. *laughter*
Because if don't have your....
If the don't wanna play nicely
build your own themepark with yes ... you know.
So make your own star!
This is what we do.
Because if the star is not nearby,
a sufficiently bright one,
well, why has it to be sufficiently bright?
Because if you want to do this computation
a thousand times a second, well,
then the time for your CCD when you record this image
for your wavefront is a thousands of a second.
And if you don't have enough photons
in a thousands of a second, well,
then there is no computation of this offset
of this little green dots on that grid.
So you need a lot of photons.
So let's get enough photons!
And there are actually two things
what you can do.
There is a conveniently placed sodium layer
in the upper atmosphere.
*laughing*
It's 19 km above ground
and there is a sodium layer.
And what you actually can do is
you can take a laser on ground here,
and then shot laser which corresponds
to the energy transition of this sodium atoms
which is 589.2 nm. It's orange.
And excited those atoms up there
in the atmosphere and they will
start to glow.
And if you have a focus,
if you focus it in there,
and than you have a blob of sodium atoms
lighting up in the upper atmosphere,
maybe... what ever some hundred meters long
and some meters wide as big as your focus is there.
This can be done with a continuous laser.
This has been done in the past.
Yes, of course.
And actually the first instruments
were build like that.
The thing is
in those days they were very, very expensive.
There is no sodium laser.
There are only Di LASERs and they are messy
and expensive.
Nowadays we can build this as fibre laser
but not ten 10 years ago or 15 years ago.
An other solution is to actually
use Rayleigh scattering in the atmosphere.
You use a Nd-YAG LASER
which is 532nm. It's green.
It's easily available, it's cheap
compared to the other one.
And then you focus it in the atmosphere.
The only thing is:
You will do have backscatter of photons
all along the way.
So you have to think about
how can I only record light from
a certain height above ground?
Because otherwise I don't have a spot,
I have a ...ehhh... a laser beam column
somewhere there.
Okay!
How do this things look like?
Can we dim these lights actually a bit?
Or is it only an off switch?
Can you check on this? Let's check on there...
Just push the button... come on...
No? No. No!
laughing
Nooo!
It's still on here...
*gasp*
All right, it's looking like this.
Who has been at the camp?
There was an astronomy talk at the camp
from Liz.
Actually if this talk had been tomorrow
we would had have a live conference
to that side because Liz is right now here
and she send me that picture
just some hours ago.
That is how the just do things on
Paranal in Chile.
The thing I will talk about
is the green one to the right.
That's the thing I have been involved with.
Yea, let's look into that.
So if you shoot the laser into the atmosphere
of course you do have problem.
The star is very far away,
it's infinitely far away.
And the light that comes down
is in a cylinder.
And if you shoot a laser up, it's a cone.
So you only probe the green region.
The unsampled volume of turbulence is to the side.
That is a problem with our laser AO.
An other problem we face is this one.
When we take a star to measure the wave front
then it passes only once through the atmosphere.
The laser beam goes up and down.
And so there is a component
called tip tilt component
which is actually just the thing moving around
It's not just the phase
that gets disturbance introduced
in the wave front but this moving around.
So not the bright and more or less bright twinkling
little star thingy,
but the moving around.
And that can not be sensed with a laser guild star.
So when ever we do laser AO
We do need an other star
to get this component.
But this star can be a bit further away,
like an arcminute or 2 arcminutes or so.
So it's that... is wide. There are enough.
And then we should think about
actually what we have to correct and so
we should make a profile of the turbulence
above ground.
And this is how it looks like.
And for example for the side
where we are there in Arizona
we see that most of the turbulence
is actually just above the ground.
So we maybe should care mostly
about the ground layer.
It's not so much about the high altitude things.
So and then what we do is:
Well we want to sample
the ground stuff nicely
so we don't take one but 3 lasers.
So to fill this area nicely.
And yes, of course, we can also combine this
and this looks like that.
This combination we will not talk about today.
We will only talk about that.
This is how it looks like.
So this is our telescope, the primary mirror
which receives the light from outer space
it then deflects on the secondary, tertiary
and than somewhere here.
But first we need to have to shoot the laser up.
And it's launched from a laser box
onto a mirror behind that secondary mirror
over there into the atmosphere
and after 40 microseconds it reaches
an altitude of 12 km.
And then of course it comes back.
After 80 microseconds it's here
in our detector again.
So the star then lights up,
has this cone, get's focused there, focus,
reflected to here
and we do have our signal in our detector after 80 ms
and as said, because of course
the laser has scattering all along its path,
you want to gate this information to 12 km
and well then you just -just- look at
when your laser pulse started
wait. wait. wait. wait. wait.
open the shutter for the detector
for short time after 80ms,
close it again and then analyse
and read out what you just did.
Easy, huh?
So we are done.
Thank you for coming to my talk
and now go out and build your own lasers
with... to...
*laughing*
Now we are going to look at this thing
which is actually build and which works.
So this is called ARGOS.
It's a ground layer AO system.
That's what we want to build.
It has wide field corrections.
That means you can not correct
just a tiny patch on sky but for for astronomical use
a huge area, meaning it's not just
a circle of 10 arcseconds but
this thing can correct 4 by 4 arcminutes
which is huge,
so all the objects that are in there.
We have a multi-laser constellation.
We have seen that why we need this,
because we want to fill
the complete ground layer.
So we have 3 laser guild stars per eye.
Why per eye?
This will be clear in minute.
And we use high power pulse green lasers.
And this deformable mirror is actually
build in the telescope system already.
The secondary mirror is the deformable mirror
which is very convenient,
because then all the instruments,
that sit on the telescope can benefit from
this system.
It's installed at this telescope.
Look's pretty odd. Yes, I admit that.
That's the Large Binocular Telescope.
It's two telescopes on one mount.
One primary, two primaries.
It's roughly 23 by 25 by 12 meters.
It sits on Mont Graham in Arizona.
And it has an adaptive secondary mirror
which is this violette coloured thingy
up there in the middle on top.
This is how it looks like.
This is the control room
where you sit.
This stays fixed.
All this shiny part rotates.
That's the actual telescope,
the red thing that moves up and down.
So the whole building rotates and it moves
up and down.
It's from ceiling... the ceiling is at level 11.
So when you actually sit there,
you can watch around a bit
... this is outside... it's winter... yuh!... let's see...
There is a ladder...
Yes, this thing is huge...eh.. nice.. cool
Okay, that's what it's looks like
when you are actually there.
Okay, our system layout is like this.
We have this adaptive secondary mirror
which is the deformable mirror.
We have the primary, tertiary.
That is clear already.
So we have a laser box.
The green things is the lasers themselfs.
So that's how it looks like.
We produce some laser beams.
We have steering mirrors in there
to get them into the right pattern on sky
of course.
We do have control cameras,
if : Is the focus right?
Is the position right?
This is one control loop
another control loop, another control loop
an other control loop.
The black thing is the shutter.
Because we have to close this whole thing,
when aircrafts are overhead,
when satellites are overhead.
So if you want to use this system,
you have to, 6 weeks in advance, you have to
put out your list of observable targets
to some military agency.
And they will tell you: Okay! Not Okay!
Okay! Not Okay! Not Okay! Not Okay! Okay!
Not Okay, meaning something is passing overhead.
Hmm... what could this be?
*laughing*
Of course, at some point the lasers
come down again in this cone shape.
They will reach the primary mirror
and ultimately it will end up
in the wave front sensor
which is much more complex than just this box.
I showed you before.
So there are aquisition cameras
which detect are we at the right spot.
Do the spots get onto the detector
in a nice fashion.
We do have to do this gating, remember?
We have to open this shutter
for the CCD when we want to record the light.
This tiny fraction after 80ms.
After the laser pulse has been launched.
It's done in here.
These are Pockel Cells.
So its an electro optical effect.
And then there is also something
in addition because I said
we can't do without the tip tilt
and there is another unit in here
that sits right in front of the science instrument
that detects this tip tilt star,
this additional star.
So you have the laser wave front light,
the green one, you do have this tip tilt light,
the blue one,
and you do have the actual science light
from the object you want to observe on sky.
That goes directly into this scientific instrument
in the end.
And then you have a lot of control things.
Of course, you do need a common clock
for this synchronization of all this pulses
and the gating and what not.
And of course you need the information
for the tip tilt component and for the wave front
into this computer
which sends then all the slops
- you remember we have to do this
linear approximation pieces wise, yes -
into the secondary mirror
which than deforms in real time.
And does this a thousand times a second.
This is how it looks like.
So when I am there I am roughly that tall.
The two black tubes right in the middle,
those are the two tubes which go up.
Looks like this.
So, this is how the components are distributed
over the telescope... once back.. okay
primary mirror, primary mirror,
some instruments in the middle,
some tertiary mirror,
the secondaries, the adaptive ones up there.
Yes, I hate to use this laser pointers.
*laughing*
Because I am always going like this... eee
(green laser pointer on the slides)
*laughing*
That's my man! *laughing*
So okay!
So we do have the adaptive secondary
up there and then it goes back on the
tertiary down there and then it goes over
into the science instrument,
all the wave front sensors and what not.
Again, we do have a laser system.
We have to place somewhere a launch system
for the laser, a dichroic to separate
between the laser light, the tip tilt light and the science light.
We do have to have a wave front sensor
to check how the wave front looks like.
We do have to have this tip tilt control.
We have calibration source.
A calibration source would be nice
to calibrate the system during daytime,
aircraft detection, yes, satellite avoidance,
-also an issue here- and a control software.
There are many people just writing...
...just haha... writing software for this.
And this is really hard.
Some are also on the conference.
They don't want to be pointed out
as I learned, but you will find them
at the conference, if you look at the right places.
That's where the laser box is located.
Just next to it is the electronics rack.
How does this thing look like?
So that is one of our lasers.
It's about 20 W. Don't get your finger in there.
*laughing*
It really hurts.
(Did you try?) No!
There is a mandatory annual laser training of course.
Yes, if you want to have something like this at home,
you do need a huge refrigerator next to it
just for the cooling of that thing.
This is nothing you want to have at home.
Just because it's... that bulky... no..it's not..
but actually when you do
this green laser pointer thingy
then there is always this always this:
"Don't use this for more than 10 seconds."
Because why? Because the crystal inside
heats up.
And if you can't dissipate that heat
the crystal at some point breaks
and then your laser pointer is broken.
This thing gets continuously cooled.
So, therefore it's a bit more expensive.
*laughing*
If you than put it up,
so this is still on the lab table
when it was integrated and tested
and than at some point it gets put all
in a box with all this control mirrors
and cameras and what not.
But finally you see in the middle
on this picture there is
a focusing lens and then you see
these 3 tiny little beam coming out of there
which than expand on sky in size
of course when they are in 12 km height
but that's how they come out of it.
And if you install this in the telescope,
you actually have to tilt the telescope,
because otherwise you can't reach it.
And then you need your climbing gear.
So once you have produced the lasers,
you need to propagate them to a through
a dust tube onto a launch mirror,
a folding mirror and from there to
a launch mirror.
Yes and then it looks like this!
Okay, so the lasers come from here into that
and then over to the other side
over the secondary mirror and then
being shot right up into space
like this.
Okay, so if you want to have that at home,
.... eh... but I can tell you the whole facility
does cost less than one fully equipped Eurofighter
*laughing* *applause*
Thank you for taking the hint.
Yeah, that's how it looks like.
It's.... yes it's... *laughing* ... yeah...
*laughing**applause* Okay?
okay... I have to admit this are a bit longer exposers.
It's not that bright and green
when you are actually at the telescope up there.
But if you have been in the dark long enough
around ten minutes, then I really becomes bright.
There is a little telescope that observes,
where actually the spots are on sky.
And if we have clear sky,
then we have this constellation on the right.
So that is how the lasers come up.
As I said you do see them all the way up,
but we are interested in the little dots
at the end.
You can barely see them.
If there are high clouds,
well than we produce something like this.
We have the dichroic when the light comes back down
as said.
Which separates the science light in red
and the laser light in green.
This is how it looks like.
Actually the dichroic is right in front of Sebatian there
and from there it gets then reflected
on a reflector and then up into the
wave front sensing unit.
So there is the dichroic, there is the reflector,
and it goes over in this unit
which is the wave front sensing unit
which sits there, at the side.
That's how it looks, when it gets installed.
And that is how it looks inside.
So you have the 3 laser beams coming
from the side, from the sky, of course.
You have patrol cameras
which monitor where are these?
Are they at the right spot?
Do we have to steer the lasers a bit?
Than we have some control for the position
of the laser spots and the field.
The Pockel cells are the ones
that do this opening and closing in front
of the shutter.
You can't use a mechanic shutter in front
of the CCD.
We have to do this electro optically
So you have a polarization of the laserbeams.
And you have a polarizer... a cross polarizer
and then you just turn the polarisation
of the crystals.
It's an electro optical effect
and then it gets passed through
or it gets blocked.
Then you also of course have this lens slit arrays
in there and then the CCD
which actually records this dot pattern.
You remember, this 4 by 4...
well it's not 4 by 4 in our case we do
have a bit more resolution.
The sensory looks like this.
This is actually a custom build CCD.
Very special.
The imaging area is in the middle
and when you read out the thing,
you split the image in half,
you transfer it to the sides
to the frame store area and than read it out.
'Cause read out is slow, transfer is fast.
And you have to do this a thousand times
a second at very low read out noise,
which is only 4 electron read out noise.
For the experts here in the audience,
this is very good.
It's not many pixels but it's more than enough for us.
So how does this look like?
It looks like that!
So there you have your pattern again,
regularly spaces pattern of course
from 3 laser guild stars you get 3 patterns
and then you analyse, well, the position,
the relative position, the absolute position
of those stars on their grid,
and somehow compute this slopes
from there feed them back, compute then
actually electrical information from them
which you can than feed into your
deformable mirror again
which sits on top of the telescope
and then hopefully everything works.
This you can digest at home. *laughing*
It's in the stream now so it will be
saved for all eternity
and all the aliens
which record all the electromagnetic field
from Bielefeld... (mumbling)
*laughing*
Anyway, so, just in short.
There is down in green there is this thing
that goes up from the lasers through
some steering mirrors.
We have diagnostics, then we got to focus
check launch mirror one and launch mirror two
onto sky and then we go back
up there N1 is the primary mirror.
And then we go through this whole chain
and there are various control loops
sitting in there.
And all this things have to talk together
on very high rates.
Sometimes you see 1 kHz other things are a bit slower.
This all needs highly sophisticated control software.
And the programmers can be real proud
of what they did in the past
with all this control loops.
The tip tilt is very... much much much easier,
because all the...
you remember this tip tilt
so this all is moving around.
So you have 4 quadrants at a little cell
and it moves to somewhere up, down,
left, right.
You can easily detect that.
That is feed into an array
of 4 Avalanche Photon Diodes
to actually record this and for that
we don't need many photons.
So this tip tilt star can comparably...
be comparably dim.
The calibration unit for the daytime calibration
can be put into the beam,
so this arms can swing over,
over the primary mirror and then we can
inject artificial stars via a hologram
into the whole unit during daytime
and calibrate this whole thing.
And than yes, we are back here.
This is how we look like.
Maybe concentrate on this two areas first.
I will flip back an forth many times.
But, yeah, what is this?
Are this two stars which are just fuzzy
and dim?
Or is this an extended object?
The upper one may be a galaxy because it's
elongated.
Okay, concentrate on that.
Well, it actually just a bunch of stars.
And this is over a huge field.
So the correction is not just in the middle
but you can see also at the very edges
of this image, we do see this improvement
in image quality.
Of course you can have the diagram, if you want.
So the blue line is without the thing beam activated,
open loop,
and if we close the control loop, to do
this measurement and correction in real time
we do squeeze all the energy into a few pixels
which of course also means
our signal to noise level in a single pixel
goes up tremendously.
Meaning you can decrease
your exposer time.
Which is important if you want to observe galaxies
at this telescopes
it's 200 Dollars a minute.
*laughing*
It's not cheap.
Okay, good so... the thing...
just last week there was another commissioning run
testing commissioning run for this system.
And my colleges José Borelli and Lorenzo Busoni
have done a nice video.
The music btw. "hallo gamer"
it's royalty for ears...
If it was now darker therefore I asked,
this would come up nicer,
but let's see!
There is sound hopefully,
so the sound guys, let's see!
*applause*
Of course this a longer exposure.
It's not that starwars like
I would have loved to use some starwars
tones along those. But you know, all those rights
and... what not... yes... anyway!
That's how it looks like.
So you have 3 laser beams per eye.
Remember, we have 2 telescopes on one mount.
They look roughly in the same direction
but still...
So if you observe two telescopes
at the same time it's only 100 dollars a minute.
Yea, This is not so much the shiny part
on the dome itself, but if you actually
do stand on the mountain during night
and are a bit dark adapted,
you see the laser beams like that.
And don't be fooled!
If you are at the valley,
or very far away you hardly see them.
You don't see them at all.
You see them there.
If you are two kilometers off side already,
it's merely a dim greenish something.
If you are down in the valley 10 km off,
you don't see them any more.
If you take a camera, 5 minutes exposer, yes!
But otherwise, No!
There is no such thing as
"The people in the valley down can see like
these lasers pew pew every night.".. and no.
Ok, which gets me to the last part.
How, do you become
and how do you work as a laser rocket scientist?
Yes, I put this in the talk directly,
because I do get this question in the Q&A, normally,
when I talk about these things,
and it's always like:
"What do I need to do if I want to do this?"
Maybe you have already an idea about this
because you have seen how complex this thing is.
And, there are so many things to do in these kind of projects
and on various levels, also in the administration,
also for senior people, new people, maybe master thesis works on that
or bachelor, or PHD or then as a post-doc.
It's very complex.
Yes, and it's not only about just shooting lasers in the end.
Sometimes it's just about checking the cables
It needs to be done.
There is a tremendous amount of electronics and electrics involved.
There are all the mechanical components in such a system are custom built.
Either the institutes built it themselves
or they give it out of house.
There are these real time computers, for example.
this is by the way our real time computer
from micrograde, if you want to look that up.
it's company. It builds these things.
They need to be programmed.
Oh, if actually somebody is here in the audience
with real hard core experience on
real time computing, coding and such things,
do talk to me!
*laughing*
Yeah, this is how our software system looks like.
A very small part of the GUIs. It's a lot of code
and a lot of work and a lot of sleepless nights
in front of these computers and just testing it and testing it
and then testing some more, and testing even more.
And, to be involved in these kind of projects,
you don't need to be a laser physicist,
because there is no one thing.
If you want to take 3 messages out of this, it's:
it's a team effort, there are many tasks,
and there are many jobs, and you have to pick one.
Because in this one job you do in these projects
you have to be very, very, very good.
Because there are other people that are very, very, very good.
If you work in these kind of projects, if you meet a new person for the first time
just assume that he or she knows everything about this
and you know nothing.
You will quickly realize if that is true.
But otherwise, if you assume it the other way round,
you just make a fool of yourself, okay?
Don't do that.
People in science, second most important thing if you really want go into this,
people in science are just like people outside science
meaning you will meet nice people and you will meet.....
*laughing*
just like in life.
It's not that these things are spheres where people are, you know
floating above the lab surface and nice coloured.
No, it's hard work.
And if you actually go into this like study physics
or maybe if you want to construct this,
of course all the drawings are done by
people how have learned this in there studies,
so "Maschinenbau" what ever...
Go for that one.
Building optics needs optics experience.
If you want to actually build stuff,
well, there are many people in this institutes
or universities who work
in the mechanical fabrication departments
or electronics departments.
They just do PCB layouting all the time.
But this things do need sophisticated electronics
and this all custom built.
This is nothing you can buy of the shelf.
Nothing of it! Almost nothing.
And this means you might end up
with something equally cool.
It's not that you can have this one thing
and then BAM ten years later you will be
the laser-rocket scientist. You won't!
You might become one
and then even after 10 years,
you might realize this is not the thing
you want to do forever.
So I have to correct
the introduction in one point:
I'm no longer working there.
I recently left.
I'm now have my own company.
I'm still involved in these things.
I do calculations for this kinds of things,
but I'm not at an institute any more,
because I decided for example for me
that the contract conditions in this type
of scientific work are not of the type,
which I want to live with any more.
Like one year contracts.
*applause*
And so there are many ways of being involved in this
and don't just... don't just focus on the this!
Focus on what you really want to do and
you might end up in this
and if you don't,
well you do something equally cool.
All right! Questions?
*applause*
Herald: Okay, first of all
thank you for our daily dosis of lasers.
I have said... Ich hab keine Zeit...
cause we have really not much time left for Q&A,
so I'm first asking the signal angel,
if there are any questions from the internet,
because... was that a 2? 2! ok.
because this people can't ask questions afterwards, soo...
Peter: I'll be all congress and if you want to reach me
directly 7319 is this telephone.
Herald: Ok, the signal angel questions.
Signal A.: Yeah, the first question from the internet was:
How strong the laser actually is
or if it could be any danger for something
in the vicinity?
Peter: Actually, no!
So we shoot up around 15 to 20 W
per laser beam.
If there was actually a plane flying through
our laser beam,
then nothing happens to the pilots.
They don't get blinded or what not,
because it's di... the beamsize at that altitude
is so big already.. they will of course look like:
"Errr what is this?"
And that's what we do not want,
because then they might push some other buttons
which they are not suppose to push.
*laughing*
If you of course work directly at the system,
you have to maintain it,
you open it, you have to align the lasers
and what not beyond there self aligning capabilities,
you do have to wear all this protective laser goggles
and what not, because if you do...
if you don't you do have instant eye damage.
It is not... no its instant.
You might not see it instantly.
But the instant... it's there instantly, period.
So really, folks, don't experiment on this
laser stuff at home,
if you are not following basic laser safety rules.
Not prying this things from the DVD burners
or no blue ray thingys "uuh does it really work?"
Just, just don't!
Your eyesight is not worth it. period.
It's not!
Herald: Please remember to cover your still working eye!
Peter: Yeah... only look into the laser beam
with your remaining eye.
Herald: The other question?
Signal A. :And the second question from the internet
was... It's actually commenting that,
this was a very cool concept already been used
and where do you see this going
in the next 10 years, so what's the outlook
for observation from the Earth's surface
in the next 10 years?
Peter: Oh, of course
the telescopes will get bigger and bigger.
The next generation of the telescope is coming up
in the 2020s.
The European Extremely Large Telescope
will be about roughly around 40 meters in diameter.
These are so huge they can't work in
seeing limited operation any more.
They do have to have laser AO all the time.
It will look similar to this.
So this is in that sense also
a technology demonstrator.
There will be a combined thing.
You may remember this diagram
with the one sodium laser in the middle
and the others outside.
So these combined things.
And then you can also imagine something,
that you probe different heights
in the atmosphere,
because you do have different turbulence layers
and all of these then have their own
deformable mirror.
So it's a very comp... gets a very complex set,
a multi conjugate AO as it's called.
And then there are of course
new... there is research being done on
how to detect this wave front
most efficently.
And there is a so called thing called
the pyramid sensor.
You can look for that, also
we do have one in our system.
And this is very efficient.
So it takes much less photons
to get to the same signal to noise level.
This is active research and... well...
Every major telescope of course now has this.
And every big telescopes in the future
will have this all over the place.
Herald: Okay, we're completely out of time. Again.
Again, so thank you very much.
Peter: Thank you!
*applause*
*postroll music*
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