Interview W.M. Keck Observatory
Interview W.M. Keck Observatory

ALPAO is proud to have the W.M. Keck Observatory among its references. In December 2022, Sam Ragland gave us an interview. He answered some questions about Adaptive Optics technology for astronomy and his feedback on ALPAO’s products.

How would you explain in a few words Adaptive Optics to children or beginners?
That’s quite challenging. I could start with an astronomy example and then see if it could be made very generic.

From an astronomy standpoint, ever since Galileo looked at the sky, he was interested in understanding the universe around us. So, the very simple idea was to collect more photons, this created the telescope. Then we built even larger telescopes to collect more and more photons from the cosmos to understand why we are here on the planet and how we came to exist. Very fundamental questions raised by humanity, philosophers, and scientists.

Quickly we realized that we live under the atmosphere that is necessary to survive, it provides us oxygen to breathe and live, but which hides part of the information that we are looking for by disturbing the light. That’s where AO comes in the picture, we correct the light wave as it enters the atmosphere to make it as if we are outside the atmosphere.

Technologies have been developed over the last few decades. It’s great that ALPAO is one of the frontliners in the industry that is making part of the AO reality. We are very happy as astronomers, at least myself I am very happy to collaborate with an entity like ALPAO to bring new technology to reality.

In what context did you use AO during your previous job at W.M. Keck Observatory?

For the specific science cases, it’s at the front level. We used it to make very fine corrections, this is called Extreme AO or XAO. I collaborated with ALPAO to take the existing system and bring it to the next level. Those projects, those instruments are mostly targeted towards Exoplanets, both characterization and detection of them.

There are other use cases and fields, W.M. Keck Observatory did a lot of work, for instance the Nobel Prize in 2020 for the galactic center. Those things were different, we cannot achieve the same levels of correction like we do for some other fields, they are fainter, you require other techniques. But still in those areas, without AO the galactic center would look like a small globe, but we are able to resolve it with all the stars in the field.

The galactic center was a very successful idea at W.M. Keck Observatory that we used AO for.

Gravitational lensing is gaining more interest now because you are able to see it. It was more of a theory in the past. Now with AO we can look at very distant targets even if you’re not correcting as much in some cases but still it’s required to resolve objects.

In the longer wavelength we did a little better but in the shorter wavelength we still have to develop AO technology further because the shorter wavelength requires finer corrections in actuator space. That’s why W.M. Keck Observatory is currently developing the 58 x 58 actuator DM. Unfortunately, that is not the end of it, we also need a faster frame rate, so there are challenges.

What are the major benefits of AO for your previous and present jobs?

Some of the things we’ve done couldn’t have been achieved without it, for example the galactic center is a good example, you don’t get the spatial resolution you need to even think about those projects, it’s the minimum necessary.

But some cases, now that you are putting all the light into a compact core, you are able to increase the sensitivity.

If you want to do spectroscopy without AO you can, we are using traditional instruments. However, if you could collapse a big blob of light, about an arcsecond wide into 50 milli arcseconds wide, you could increase the light throughput of your instrument.

Most of the science cases though, we wouldn’t even be able to think about those.

It’s really hard to imagine Astronomy without AO now?

Yes, especially any telescope larger than say 4 meters it’s almost not possible to do meaningful Astronomy. Just be careful in the sense that there are people working in Cosmology who look into the old universe who don’t really care and just want to collect more light. There are some projects but most of the projects you are right, without AO you wouldn’t be competent.

What would like in your dreams as next feature from Adaptive Optics systems?

Ideally, I would see AO become like a black box. I am a developer, I’m an astronomer, scientist but I spend most of my time doing development for AO, to make it work, maintain it. I visualize AO becoming like a plug and play. Have it fully integrated into the telescope so that you don’t have to work too hard to do basic things. But while still pushing performance to the limit.

How long have you been working with ALPAO?

I think about 3 years I would say.

What advantages do you see in our products and technology?

The ALPAO approach likely gives you enough dynamical range for most of the application, so there is a good potential.

Having said that since I work in the XAO it is very hard to dimension. Perhaps we have to go for two-stage systems. There’s a space where ALPAO has a clear role to play and is already playing.

Could you let us know where the mirror is used and what for?

There is two telescopes at W.M. Keck Observatory, Keck I and Keck II. We will take the existing mirror of Keck II and replace it by the ALPAO one. It will be used for all kinds of AO observations.


Sam Ragland earned a Ph.D. in Physics from Physical Research Laboratory in India and held postdoctoral appointments at Arcetri Astrophysical Observatory, Observatoire de la Côte d’Azur, Indian Institute of Astrophysics, and Harvard-Smithsonian Center for Astrophysics.

He was Senior Adaptive Optics Scientist at the W. M. Keck Observatory.
At the W. M. Keck Observatory Sam held staff and leadership roles with the Keck Interferometer prior to shifting his focus to adaptive optics. He has an extensive record of accomplishment in astronomical instrumentation and its applications, reflected in publications and grant funding.

Now, Dr. Sam Ragland as the Observatory’s new Adaptive Optics Head at the Large Binocular Telescope Observatory. In his new role, Sam is responsible for managing the operations of LBT’s existing AO systems and leading the development of new AO initiatives to enhance the scientific productivity of the telescope.