AO4ELT7 Days -5 to -2: The CDI Prologue, AO-istas in France

First stop after the plane, because how else will the people know we’re in Paris?

This is the prologue to the long sweaty conference the XWCL team will be spending in Avignon, in which some of us spend a shorter but just as sweaty time at a workshop in Paris. (There is a heatwave here, and it’s humid, and the desert kid in me is struggling to adapt.). Last year Sebastian, having good ideas as he does, collaborated with other high contrast imaging folks to think up a workshop on Coherence Differential Imaging, or CDI. As the whole point was to entice the next generation of instrumentalists with the siren song of coherent starlight subtraction in control and post processing, I was an easy target to convince to attend. Jared, having never been to Paris before, was also more than willing to spend a few days in the discussion. So here we are, tourists in a world-dominant optics hub.

Day -4: What is CDI again?

“The Castle” – Observatory de Paris, Muedon

The first day of our CDI journey gave us a late start and a delightful Uber driver, who not only saved us from walking up a long hill to the conference location, but also regaled us with a deep dive into just how bad the drivers there really are.

We found that big tower again from the suburbs.

The Observatory itself was nestled overlooking over the city from it’s Parisian suburb, magnificent among the larger park and woods that presumably came with the original estate.

Overview talks included the Self Coherent Camera (SCC) design.

We started the day with a series of very helpful overview talks, in which I rapidly went from not even really knowing what CDI stood for to appreciating cutting edge efforts to use the coherent properties of starlight with our high contrast systems. Barnaby Norris, Sarah Stieger, Axel Potier, and William Thompson should be commended on how much effort they put into the breadth and depths of their review talks. If you had listened closely, over the birds and the beatific breeze, you would have heard my brain expand three sizes in just an hour.

Pastries for thought.

Almost as helpful as the actual programming were our extended coffee breaks, catching up and floating ideas with some of the leading experts in the field amid delicious pastries. It’s a good reminder that no matter how deep in the trenches I am with my little calibration codes, plenty of my colleagues in the field are right there beside me, banging their heads against similar walls.

Gratuitous pictures of snack tarts and our struggles with slicing them.

At the end of the day we snuck in a little solar observing in an H-alpha filter. What a welcome sight to see the small saguaro on the solar telescope, designed and built by Lunt Solar Aystems in Tucson Arizona! With that petite piece of home, this place started to feel familiar.

With just this little guy we saw stellar prominences in great detail.

Day -3: Discussions and downpour

We did ask Sebastiaan if he wanted an umbrella…

Our second day was focused on hands-on teamwork exercises, which the MagAO-X team prepped for with the team exercise of figuring out how to get on the train, in the rain, from the wrong end of the station. It made us miss our chatty uber driver, especially with the quarter-mile hill treck from the train station to the workshop. Sweaty and drenched and a little dazed, we quickly got into our day of working through simulations and practical implementations of CDI algorithms and architectures.

a quick look into the wavefront correction on THD2 – To the left, the pupil, and to the center the PSF

One of our hands-on notebook experiences allowed us to play with the test bench right here in Paris. Their team has done great work to show a possible use case for AO telemetry, and in some of them we were even able to use their complex coronographic phase mask to pull out the planet!

Using a model of the THD2 test bench and well-calibrated telemetry to reconstruct a PSF, and a planet!

After the day wrapped up, and to much nicer weather, Vincent Deo, a Paris local, walked us through the Meudon streets to a delightful sidewalk restaurant. There, discussions continued, though perhaps on much sillier topics, over wine and Belgian Beers and Charcuterie.

Cheers to charcuterie

Meanwhile… word has reached us that the Space Force AO4ELT contingent has arrived on the other side of France …

Day -2: Reflect, Revise, Repeat (in 2-3 years?)

Sebastiaan and I finally made our train, and made it to the workshop mostly on time

And before you know it its over. We wrapped up our discussions on the final day, summarizing our progress, thoughts, and future projects to the rest of the attendees. It was required that the students do the talking, and because of that the final presentations had much fresher face than the introductory ones. It did feel like

Thank you to our LOC and SOC for being such wonderful hosts!

Of course, for all we’re learned, it was also a treat to be able to see another world center for astronomy, and another old telescope. Though this site is mostly for solar observing in the modern day, it has a history of observing that you can feel wandering the halls.

The original Lyot Coronograph

Finally, we finished this productive and educational tour de force with a very french dinner. More cheese, duck, and good friends from California and Australia.

Everyone but XWCL looks good in this picture, so I guess we’ll use it.

See you all soon in Avignon!

Song of the Day(s):

Blog Rules for the french trip: Every post should use at least one french word, have a song of the day, and be tied to a memory of the trip.

Summer Breeze by The Main Ingredient

The streets of Meudon were perfumed by the many jasmine bushes, wafting along a puff of breeze. I can understand why they’d want to host a workshop out there.