Ok, so Céline, what are you working on here at the moment?
So this is an adaptive optics experiment.
It's not meant to be used for astronomy, but it's going to be used for another
project dealing with space debris tracking and the orbiting.
So we're actually going to use lasers to get rid of space debris?
Yes, they use a powerful infrared laser that they shine at debris
and they do imaging and they can determine based on the time of flight
of the light to the debris and back, what's the orbit and it's actual location.
Now the key part of any adaptive optics system is a deformable mirror.
I believe this is your deformable mirror here. (Yes)
How does this work?
So this mirror deforms in real time. It's got some
actuators in the back that can push and pull and deform the front surface here
and it runs about a kilohert. So a thousand times a second, you'd change the shape of the mirror.
So the other crucial part of an adaptive optic system is a wavefront sensor. You have to
know what the distortion of the waves are before you can correct them. Where's that?
So this is this camera here. It's a very powerful camera that can detect single photons
and it's got a lenslet array right here in front of it and that's where you actually do the image analysis.
So what's a lenslet array?
It's a tiny piece of optic that is like an array of miniature lenses.
One adjacent to the other and you can analyse what the shape
of the waveform is based on that.
Right. Thankyou.
So, Francois and Céline...
you guys helped developed what is the most advanced adaptive optics system in the world right now
which is the GeMS system which uses five lasers at a time. Maybe you can explain a little
bit how that works. And Francois, why don't you start out about the adaptive optics and
then you can tell us about the lasers.
Yes, well one of the limitations of classical
adaptive optics is that it corrects for the atmosphere aberration but in one direction.
So if you look away from this direction, if you move off, it's going to be a little bit more blurry.
So that's clearly a limitation because people, you know, are interested in
imaging and correcting the whole... the largest field possible. So there is this new technique that
appeared at the end of the 1990s, that is basically using tomography techniques
like when you're imaging the brain, for instance. So you are taking information from different angles
and then from this information which is 2D information, two dimensional information
because it's taken from different angles you can actually install the 3D contents of your information.
And therefore, if you have three dimensional information about the atmospheric turbulence
you can also correct it in a 3D fashion and therefore you correct it in any direction.
So what it does is that effectively it enlarges the field which is accessible
with the adaptive optics improving its quality.
Ok. And that instrument is now working, I believe.
Yes, its been very very challenging because as you say it has five lasers
it has three deformable mirrors and five waveform sensors.
So there's physically classical adaptive optics, multiplied by five
and the complexity also went up with maybe not by a factor of five, but at least a factor
of two or three. So, it's a very complex system. And it took some time and effort to make it
work, but eventually it was working, and delivering, you know, very very nice results.
And Céline, that laser system... I remember seeing, trying to get the laser system there. But once you
get the laser system working in California, how do you get it working on top of a telescope
in the middle of Chile, night after night? And how does it work, in detail?
Well, you need to have a team to support operations, so typically there is a dedicated laser engineer
who is in charge of making sure everything's going to run smoothly, and he works with two
laser technicians so that before a laser run, typically it runs our schedule in periods
of, say, seven to ten nights in a row. So before the laser run, they'll start the laser
realign it if it doesn't perform as well as it should, and then during the run they're going
to be there operating the laser system and making sure, you know, everything goes smoothly.
Ok. I'd like to finish off by asking, where do you think the future of adaptive optics
is going to go? What's going to happen in the next few years? Is it going to get drastically
better, or are we already close to the limits?
Oh, no no. There's still room for improvement.
One of the next very very interesting adaptive optics systems that's coming online is actually
a GPI, which is coming online in a few weeks at Gemini South, so at the same telescope
as MCAO installed right now. And GPI is an adaptive optics of a different kind. Instead of correcting
a wide field well, it does an extremely narrow field, but extremely well. So it means that
there will be, it will correct 99% of the atmospheric turbulence, leaving only a
very very small residual. And this is for planet detection. GPI stands for Gemini Planet Imager.
A lot of people are actually extremely anxious and impatient to see what this system is going to deliver.
So we'll know in a few weeks.
Great. Thankyou very much.
You're welcome. (Thankyou)