[applause]
-Francois: Good evening.
So Chris has been talking about the telescope itself and the science.
Jon has been talking about the instrument that receives the light.
And I'm gonna be talking about something which is in-between,
which is called adaptive optics.
And adaptive optics, as I will show you, is something,
a kind of instrument that pulses the light,
cleans it so that the instrument can actually take advantage of the full resolution,
the optical resolution of the telescope.
So, Australia, in the past years, have been,
we've been developing expertise in adaptive optics
and that's actually one of the area
where we feel we can contribute in a major way to GMT, as I will show.
So, what is adaptive optics and what does it do?
Well, Chris told us that when you build larger telescope, of course
it's to answer fundamental question about science.
But how does it do that?
Well, you build larger telescope because it's going to collect more light--
of course, that's an obvious point--
but something you have to know is that when you build larger optics,
the amount of detail that you can see in your object also grows.
And it grows inversely, linearly with your,
the diameter of the telescope.
Meaning that, if your telescope diameter increase by a factor of two,
the amount of detail you will be able to see in the image
is four times the amount of detail you are seeing with the initial telescopes.
That's illustrated by this slide here,
where this is your, an image that you would see with the VLT,
which is a ground-based telescope.
This is an image that can be seen, actually noticed, by the HST,
the Hubble Space Telescope,
which has a diameter of two point five metre.
So now, if you go to this eight metre telescope on the ground and
you apply the optics and you just forget that there is atmospheric turbulence,
then you can see many more details.
You can see deeper,
you can see the exposure now is going down to a 1600 second to a 160 second,
which gives you some more details.
If you go to this extremely large telescope,
that's what it will provide.
It provide, you know, many, many more detail.
You can see many, many more details
and it's the same as saying that
your angular resolution is actually increasing quite significantly.
And on top of that, of course,
because you have a larger collecting area,
your exposure time decreases quite significantly.
We demonstrate, you know, more of having larger and larger telescope.
However, what's bad when you have a ground-based telescope,
meaning a telescope which is built at sea level, on the ground,
and not in space,
it that you're going through the light
coming from astronomical object is going through the atmosphere.
The atmosphere is bad for astronomical imaging
because what happens here,
what it does essentially,
if you look at this star here with a large telescope
and you blow it up, you know,
many, many times, you're kind of zooming on the star,
what you see is that.
And that's the effect of atmospheric turbulence.
So, it's the same as if in summer,
you are looking at a distant object across a desert or across a parking lot,
you will see it's moving.
The image is moving.
Well, it's exactly the same when you are looking at stars.
And so, in effect with this,
the image that you had before
with this atmospheric turbulence in now transformed into that,
which is a blurry image.
In fact, the fact is atmospheric turbulence blurred the image
taken from the ground,
it does so so that the angular resolution of a 25 metre, for instance, the GMT,
is actually not better than the resolution
that you would get with a 20 centimetre telescope.
So, of course you have many more photons,
but if you don't do anything about it, if you don't have a better angular resolution,
which means that you won't see more details.
So, to solve that situation you can do two things:
you can go in space where you don't have anyturbulence,
you don't have any atmosphere,
but it costs a lot of money.
I mean, typically a space mission are extremely good,
but they cost about a hundred times more than an equivalent telescope on the ground.
Or, you can try to correct for this atmospheric turbulence
that has induced this blurring of the images.
So, that's what I'm saying here
and I'm going to demonstrate to you how we do it,
but adaptive optics can fix this
and restore the ultimate resolution of your telescopes.
OK, so how does it do it?
Well essentially, it does it with two main optical element--
two main elements, I would say.
One is what we call a wave front sensor,
which is in fact, you could call it light wave sensor.
So what it does is that it look at the star
and analyzes the information of the light wave
that is being induced by the atmospheric turbulence.
And then, this information is processed by computer and sent to deform,
the deformable mirror that wobbles and counteracts.
In fact, the effect of the atmospheric turbulence
so that when the light--
the distorted light-- bounces off this deformable mirror,
it's straight again.
And therefore, allows you to reach the ultimate resolution of your telescope.
That's a technique that's been around for about 25 to 30 years.
It was first developed by the military in the US
and then applied to astronomy about 22 years ago.
And recently, it's been also applied
to medical imaging other type of science applications.
Alright, so it exists.
It's been around as I say for 22 years.
It's installed in most of the 8 metre
and even all of the 8 metre telescopes in the world
but a couple.
And that's actually the real result that you can, you can,
but they have both for instance in the Gemini eight metre telescope.
So this is what you get looking at this globular cluster
when you don't use adaptive optics.
And if you adaptive optics, that's what you get.
It demonstrates very, very clearly that with adaptive optics,
you see first more details,
then many more details, but you can see also deeper.
Because, OK.
Here you see all of these deep, very faint star,
either you don't see them
while it reveals the faint star here with adaptive optics.
Another very nice example is, for instance, by Keck Observatory
that Chris was mentioning earlier,
this is an image of Uranus without and with adaptive optics.
So you see the really striking difference.
So, one thing which I like to show because it's very nice is that
this is related to Laser Guide Star.
And I'm sure that if you have read about adaptive optics,
you have heard about Laser--
something that you might see within the next couple of years at [inaudible]
because we are developing also a system with Laser Guide Stars
for different application.
But it's something which is related to the need of reference tools.
As I was saying you have light wave sensor.
So, if you have a sensor,
you have to have a signal
and the signal is provided by a nearby guide star,
or a star-- just a star.
But sometimes, you're looking at a fraction of the sky in a direction
where there is no guide star.
And then, well, you [inaudible] to get a star you couldn't do anything.
You just go to somewhere else.
Well, now there is what we call Laser Guide Stars
that when if you don't have a star
you can create your own star to be your reference signal.
And you do that by actually shining a laser,
which is at the sodium wavelength,
is the same orange wavelength that you have in traffic lights.
And you actually excites sodium atoms that are 90 kilometre above ground
and they fluoresce, they shine,
and you can see you can collect some of the light.
And it serves as a guide star.
So it's extremely nice
when you go now in many, many sites you can see guide stars.
This is a picture-- long exposure picture--
taken at Gemini.
And I also have a movie which shows, that's actually,
it's being taken at Mauna Kea in the -- in Hawaii.
One of the Gemini telescope is there to which Australia has partnership.
And you can see that those are the two [inaudible]
they are pointing toward the galaxy center there.
They were using laser guide star.
And another big success actually with the discovery of the black hole and--.
Oops, OK.
So it's actually quite impressing because at the top of Mauna Kea
you have now four telescope having laser
and sometimes you see the four laser shining at the same,
during the same night.
So it's quite impressive.
The bad thing about laser is that other people know where you are pointing,
so you cannot hide it anymore.
[laughter]
Alright, so this image is dear to my heart because it's an instrument,
first of its kind was [inaudible] for that, Gemini.
Actually, AO, adaptive optics of the first concept,
but now it has diversified into different breeds.
So, you have the adaptive optics, for instance, for moderate resolution gain
but very wide field.
You have other adaptive optics to study planets
that are very, very small field,
but you go toward very, very high optic image quality.
That's an example. It's actually one of the most,
I think, exciting application of adaptive optics because now,
for instance, this is the brown dwarf GL 299
as it was discovered by Palomar, an image by HST.
And this is now what you can do from the ground with eight metre telescope.
You see how, how far, how superior this is compared to even space
because of the nice control of the light and how it's scattered.
And finally, so, as I said earlier,
the strongest expert in adaptive optics is in Australia.
There is three instruments plus a Laser Guide Star Facility and is for GMT.
And we, I hope that we'll play a major role in two of these--
these are laser tomography in adaptive optics and laser guide star facility.
And finally, OK, so this is simulation, a simulation.
This one is not a real image of what we should achieve with the GMT
with adaptive optics.
Without, sorry, and with adaptive optics.
And finally, my paragraph is to say that aside this GMT activity,
we are also applying this knowledge to other thing, like for instance,
we are participant at the ANU to the Adaptive Optics Research Centre
for space and beyond management.
We're applying adaptive optics techniques to track
and eventually maybe de-orbit some of the space debris,
so that's a very interesting application.
Thank you.
[applause]