Author: Joseph Long

Last Friday, MagAO-X underwent a pre-shipment review. This is the process by which the Magellan Observatory ensures that we won’t waste everyone’s time by shipping our instrument to the telescope. It’s a multifaceted process, evaluating everything from “does your instrument work in the lab?” to “have you baked your shipping crate?”

I’m happy to report that we’ve cleared this hurdle, meaning we’re taking MagAO-X to Chile for the 2019B* run! Many thanks to all of our reviewers and the observatory staff for productive discussions and suggestions. We look forward to getting on sky with MagAO-X this December! (Since this is the MagAO blog as well, it bears mentioning that we’ll be there in November too.)

* We use ‘A’ and ‘B’ to refer to the former and latter halves of the year, since “winter” means different months depending on your hemisphere.

Also, this means Jared feels it’s finally acceptable to hand out the 2019B mission patches I designed:

The patch depicts a viscacha, one of the local fauna of Magellan, perched on a rock at sunset. (As they do.) In the sky above, a point source is diffracted by some telescope spiders to form a stylized Magellan PSF. (Or possibly a MagAO-“X”.)

As long as I don’t run out of South American animals, I plan to do a patch for every run. Then I’ll put them all on a vest and look like the world’s nerdiest boy scout.

Part of being in the XWCL is following the P.I.’s rules:

1. No unauthorized use of the label maker
2. No coding in MATLAB
3. No circus activities
4. No volunteering for Olivier
5. No metric shit running around in the lab
6. Every post must have a song of the day
7. No unauthorized use of the label maker

I regret that I forgot rule #6 in my last post, so I will take this opportunity to rectify my mistake with two songs of the day.

I’ve been digging this song about not being too hard on yourself by Alex Lahey:

And if I had been thinking about a song of the day for the back-to-school post, it might have been “Restart” by Little Daylight:

Hasta pronto.

Tucson in the summer is a bit like this, only less exciting.

However, summer is waning. (Why, it’s only 99ºF at 7:00 p.m. as I’m writing this!) Tucson is filling back up with new and returning students, and I’m no longer guaranteed a table to myself at my favorite coffee shop.

This semester, we are happy to be welcoming two new graduate students to the group!

NSF Fellow Logan Pearce (whom you may remember from this special guest appearance) is joining us in the Department of Astronomy from the University of Texas at Austin. And Maggie Kautz, another NSF fellow (and recent graduate from The University of Arizona) will now be pursuing her Ph.D. in Optical Sciences here and continuing her work with the XWCL. She was in Baltimore all summer working on the HiCAT testbed at Space Telescope Science Institute. Welcome, Logan, and welcome back, Maggie!

Meanwhile, in the lab, we’re sitting in the dark and occasionally pointing at things.

The final integration of the software and hardware for MagAO-X continues at a breakneck pace, with the number of tasks remaining before first-light described as “countably infinite”. I’d elaborate, but there’s so much to be done! More to come soon.

As of today, our 2040 actuator Boston Micromachines MEMS deformable mirror (BMC-2K DM, for short) has been moved to MagAO-X instrument optical table. With a cost of roughly three houses, it’s by far the most expensive piece of the whole project. (If you don’t count paying half a dozen graduate students for half a decade.)

So, why is it important? And what makes it so expensive?

Adaptive optics involves first sensing the shape of an incoming wavefront of light to determine aberrations, then deforming a reflective surface to perfectly cancel out as much of the aberration as you can. So, as you might guess, a deformable reflective surface is key.

Extreme adaptive optics is an informal term for the next stage in the evolution of adaptive optics for astronomical high-contrast imaging. We’re running our system faster than predecessor systems like MagAO (in terms of the number of measurements and corrections each second), placing more stringent tolerances on all of our optical surfaces, and using more actuators on our DM. Unlike the MagAO system, which deforms the telescope’s secondary mirror directly, MagAO-X uses three DMs placed at images of the pupil within the instrument enclosure.

The first DM in the optical path, an ALPAO DM97, is a large-stroke device, meaning it can deform a whole 80 µm from one edge to the other. This is about the diameter of a human hair, which doesn’t seem “large”, but for H-alpha (0.656 µm) photons 80 µm is over 120 wavelengths. The flip-side is that it has only 97 actuators. We call this the “woofer” by analogy with speaker systems, since it can only correct aberrations with low spatial frequencies.

The last DM the light will encounter before being imaged onto a detector is another ALPAO DM97. This one is tasked with squashing “non-common path” aberration: basically, any aberrations we’re introducing ourselves within the instrument that aren’t being sensed by our wavefront sensor.

The device we moved today is the “tweeter”, responsible for correcting the high-spatial-frequency modes that generate speckles in our images. These speckles can look awfully similar to planets, and can even persist in a quasi-static way in a series of images. After we’ve taken out the low-frequency content with our woofer, the residual aberration is smaller amplitude but higher frequency.

Our BMC-2K DM lets us cancel out these aberrations to a high degree, resulting in more control over speckle-causing aberrations and less light lost from the core of the image of each star or planet.

Thanks to Jared Males, Kelsey Miller, and Lauren Schatz for the patient explanations that informed parts of this writeup.