After 13 straight days of nearly perfect cloudless photometric conditions, we woke up to this today.
The first clouds of our run.
So, of course, we decided to go on sky for the first time.
Earlier I caught the grown ups attempting to run the system by themselves. That's Simone Esposito actually operating a Pyramid Wavefront Sensor, and Laird Close taking data with the world's virst diffraction limited visible imager on a large telescope. Phil Hinz offers encouragement and advice. I'm pretty sure this was when tonight's plan was hatched.
We haven’t completed all of our internal calibrations, but going on sky will let us see if they are valid so that we can complete them with confidence. Furthermore, there are many other things we can learn by looking at a real star, with a moving-pointing-guiding telescope. To do this, we had to pull off our calibration return optic (CRO), a.k.a. The Crow. We decided that tonight was the night at about 4pm. The LCO crew responded – Juan, Mauricio, and Pato sprang into action to help us pull the CRO and get the telescope ready. So by dinner, all we needed was a sunset.
After a quick chicken dinner, we just went up and closed the loop.
The complete MagAO system under an evening LCO sky.
Ok. It was harder than that.
The PI ponders the possibilities. All of them.Alfio closes the MagAO loop for the first time on-sky.On-sky closed-loop pyramid pupils. The bottom plots show ASM status.Jared with VisAO's first light.First light (at Magellan) PSF for Clio2.Later we looked at a binary. This let us verify that our rotations and platescales are about right.
Thanks to everybody who helped make this happen. We’re just getting started, and there’s lots more to come. Stay tuned!
Some quotes from today:
Laird: “We didn’t come here to get Lucky. We came here to be good.”
Povilas: “We have a situation here, where you’re arguing both sides.”
Simone: “Yes. I’m trying to sound wise.”
Laird: “There had better not be any frisbee tonight.”
Katie: “We’ll never run out of cookies.” (seriously, there are a lot of cookies up here)
We passed a big milestone today with the ASM working in closed loop with 400 modes at 1 kHz (the most complex AO mode)! This 400 mode interaction matrix has been made possible by the excellent trouble shooting from our friends at Arcetri Observatory, Simone, Enrico, Alfio, Armando and Marco!
It was such an exciting event that Alan Uomoto made a movie:
How did this happen? Well, yesterday the AO loop was struggling to close on the bumps we were referring to as Viscachas:
The Viscacha is a bump causing a dark spot in the Pyramid pupils at around 2:30 o'clock.
When the loop tried to close on this, we would get a higher and higher unstable patch of actuators trying to correct it:
Here is the ASM display after closing the loop yesterday on 200 modes at 600 Hz. You can see the commands on the bad patch at ~2:30 o'clock; the mirror is working hard to correct something there, but we didn't know what.
So Simone and Enrico figured out that we were actually getting cross-talk from the Pyramid, because the phase bump was so high. This is similar to a quad-cell Shack-Hartmann without a guard band, where a subpupil may wander into an adjacent subaperture. Here is Simone’s drawing where he works out the solution:
Simone's drawing to solve the problem of the viscacha
So the solution is kinda a hack, whereby we applied a negative sign to the interaction matrix for that patch — and the bump and the viscacha disappeared!
Evolution of the Viscacha -- Final rendition, all corrected!
And so tonight we were able to close the loop with our new interaction matrix, and get a nice flat wavefront!
Result: Closed loop, flat wavefront, no viscacha!
New arrivals today: T.J. Rodigas (Steward) and Runa Briguglio (Arcetri).
Sorry for the tardiness of this post. The internet was down on the mountain when the night shift went to bed this morning. The day was a struggle, but we finally got at least something working, and then did some testing through the night.
The issue was a feature in our pupil which Simone has dubbed the Viscacha.
Our Pyramid pupils from this afternoon, with a Viscacha head clearly visble.
We tried several things. One quick and dirty modification was to remove the field stop for the Pyramid. Simone and Enrico climbed into the NAS to do this – after first convincing Laird that this was a good idea.
Simone and Enrico perform minor surgery on the NAS.
The day shift ended with a somewhat working 200 mode interaction matrix. So the night shift did some closed loop testing.
Katie at the AO operator's workstation.
Things are hopeful. With only 200 modes we have a fairly high Strehl ratio PSF. The problem is keeping it stable. These two videos, taken with the VisAO CCD 47 at 32 fps, show this.
Youtube noted that my image was shaky, and asked if I wanted to fix it. F*&!$^ you Google. Here’s the same data set, but keeping only the best 5% of the images (Lucky imaging style).
After breakfast Laird reduced this data by “shifting and adding”. Here’s what our images will look like soon:
Our SAA z' PSF with a Vischacha contaminated 200 mode IMAT.
To try to control the vibrations that even Google noticed we put the Clio rack on some foam pads. This improved the power spectrum, at least removing the ~2 Hz spike.
The CCD 47 spot x position power spectrum after putting Clio2 electronics on some foam to isolate the pump.
Quotes:
Simone: “Laird, take a seat. You want to take your seat. I think we need to remove the Pyramid . . . field stop.”
Tyson: “Why don’t you just say you’re a carnivore plus vegetables and cheese.”
Laird: “I thought you were trying to take the frisbee away.” (To Phil, after realizing that Phil was playing frisbee with grad students and the post-doc.)
Phil: “I was just trying to help them meet their 100 hours for the week.”
Simone, on the viscahcha in the PWFS pupil images:
“The viscacha again!”
“There is a clear viscacha.”
“It is not a dynamic viscacha, it is a static viscacha.”
Laird: “It looks like a viscacha that’s been run over by a car.”
Simone: “Yes, but it’s still a viscacha!”
Laird: “I’d really like a headless, tail-less viscacha.”
"Wild" viscachas from the backside of the telescopes. Wild as opposed to the "tame" viscachas who live in the ASB.A group shot of the first wave of the MagAO team. Armando left us this morning, so yesterday we gathered the team for a group shot. We'll repeat these as people come and go. From the left, front row: Marco Xompero, Alan Uomoto, Laird Close, Katie Morzinski. Back row: Armando Riccardi, Enrico Pinna, Alfio Puglisi, Simone Esposito, Jared Males, Tyson Hare, Phil Hinz. (Not pictured: Derek Kopon)Ya-Lin and Kate joined us today. Time to get to work.Phil, Laird, Ya-Lin, and Kate wait for the green flash.
Usually an AO system has the opposite problem: There are aberrations you can correct but not measure. And of course, there are all sorts of aberrations you can neither measure nor correct, like the very highest spatial frequencies. (And if you don’t have enough stroke, you can saturate your attempt to correct an aberration — but that wasn’t the case today.)
Contemplating and debating the riddle
But today while we were making our interaction matrices, we found we had 3 high spatial frequency dots in our pupil images (a couple times the size of an actuator) and we spent some time trying to track down whether they were phase or amplitude, and whether it was a dirty optic, scattered light, or misalignment.
Pato takes Enrico up in the scissor lift to inspect the optics
Jared had to power-cycle the CRO controller, and so he and Armando went up on the scissor lift to check if the CRO was in the right position and to inspect the optics.
Jared and Armando on the scissor lift, checking if the CRO motors are working properly
When we closed the loop, these “dots” could not be corrected. We tried shifting some optics to see if we could move the spots, and we concluded they weren’t an amplitude error (too bright). Finally, we tried setting the ASM back to an older flat shape — and the dots disappeared! This means that these phase errors were somehow introduced to the system at the time we were calibrating the interaction matrices. So then when we closed the loop, we were driving toward that shape — not toward a true flat.
So the answer to the riddle is, the shape you can measure but not correct is an error in your null!
Now that we’ve solved the riddle, tomorrow we’ll re-do our interaction matrices with a flatter null.
Vizzy contemplates the calibration riddle from her perch
Yesterday:
Simone: “Hey, I think we should try taking the pyramid out.”
Laird: “No.”
Armando: “No.”
Phil: “No.”
Jared: “No.”
Katie: “What? Is he serious???”
Today:
Laird: “Hey, maybe we should try taking the pyramid out.”
Simone: “No. The last thing we want to do is take the pyramid out!”
