MAPS Oct. 2025B Observing Run: Nights 1-6

We’ve just come down from a 6 night MAPS run at the MMT. We had 5/6 clear nights and figured out what we need to do to improve AO operations with CACAO. We also completed testing offloading the first THREE modes (tip, tilt, and focus) to the azimuth mount, elevation mount, and hexapod. Finally, we have two distinct nod positions working — next up on that will be arbitrary positions.

Alignment: Over the summer we built a new telescope simulator to output an f/15 beam for testing. This enabled us to build a matrix for nodding with the periscope quite well. Unfortunately the Vis PyWFS pupils were too small and thus we are not certain the beam was, in fact, f/15. So instead we planned to spend the first night or two doing on-sky alignment. This is all an attempt to more precisely conjugate the Vis PyWFS to the pupil of the telescope.

Vis WFS: Early on the first night we tested the CCID-75 and it was working. Later we power-cycled it… and never got it back up. We could see that it was reading out, but it would not accept commands over the serial. We are now getting help from the manufacturer. For the run we switched to IR WFS.

IR WFS: On the second night we switched to IR WFS. But we couldn’t communicate with the Saphira, so during the third day our crew came back up and discovered that two fibers had been swapped. After replacing those, the Saphira worked great and we were able to operate the IR WFS for the entire run. Hooray for having two wavefront sensors!

On Night 3 we completed on-sky alignment with a working IR WFS and by centering the beam on the dichroic by eye (with a card and target). We carried on to CACAO. Unfortunately we were seeing a lot of noise in the slopes step. During the next day our software engineer discovered a bug because the pupils were closer to the edge so there was a bit depth problem.

Side note: the pupils were closer to the edge because they seemed to be larger. So something about our realignment with Vis WFS was also upstream of both and caused the IR WFS pupils to be larger — does that mean we changed the f/#?

On Night 4 now we were aligned, our camera was working, and our software slopes calculation was working, we were able to close on 20 modes and work on bootstrapping to higher modes. We decided we needed to turn on offloading to make sure we had enough stroke to put on a higher signal in the calibrations. So we spent some time to finalize the focus offloading to the mount (had already done tip and tilt) to the hexapod. By the end of the night we got a good 20 modes reconstructor on the IR WFS.

On Night 5 we continued to bootstrap to higher modes, going up to 50. This included testing ways to increase the amplitude of the calibration poke, but modally: We simply multiplied the lower orders in the basis set that we were applying. We also had difficulty with the pupil tracker at one point when we went to a new star and the pupils drifted. By the end of the night we had taken a new 50 modes calibration, but the selfRM was clipped above 32 modes due to a software parameter set somewhere that we couldn’t find ourselves.

On Night 6 we were completely clouded out. But we worked on the software, and on our user manual.

ASM testing: Our instrument scientist took telemetry at various elevations and with the mirror power but uncontrolled, vs. controlled at the flat shape. He found that there wasn’t much difference in elevation, but the outer rings move a lot when uncontrolled, indicating the noisiness at the edges where air damping doesn’t work and velocity damping is needed.

All in all a very useful run for making progress on AO performance!

Song of the run: “If All of the Raindrops” by Old Town School of Folk Music:

MAPS Jun. 2025A Night 5: 100% efficiency

Tonight we tested the new ASM-cooling fans for introduced vibrations:

It was a great time to do this test since we were getting E-stops on the ASM from some overheating actuators. We found that the fans did not introduce appreciable vibrations that couldn’t be taken out by the AO, so we went ahead and turned the fans on for the rest of the night!

We then analyzed the test we did yesterday where we took 5 RMs and compared them to make sure the RMs are actually repeatable modes. We found that they were modal and repeatable!

The next thing was off-loading focus to the hexapod.

And then we tested a 50-modes loop with the IR WFS:

And took some data:

We had some over temperatures so we paused to let the ASM cool down. But the fans were helping because this is no where near the amount of pausing we had to do last June.

And that’s the end of a great run where we made a lot of progress working on CACAO and the IR WFS, and the first run where we’ve had 100% efficiency! 5 nights on the schedule, 5 full nights of clear skies, good weather, and working instruments!!!

The song of the night is “Bridget’s Song” by Celia Farran:

MAPS Jun. 2025A Night 4: RM modes

Tonight was another beautiful clear night. Seeing ranged from around 1-3 arcseconds. At the start of the night we were confused why we were seeing very little AO correction — it turns out the TT mirror was not modulating, oops! After this we took several sets of AO-on vs. AO-off Pisces data. We also compared the response matrix modes for a set of 20-modes-RM taken with 5 trials and it is encouraging that we are seeing the Zernike-ish modes as expected!

The song of the night is “Num Num Cat TikTok Chain but its actually good lol”:

MAPS Jun. 2025A Night 3: IR CACAO

The return of IR WFSing! After squashing some software bugs we closed the loop on 3 and then 20 modes with CACAO using the IR WFS:

I’m back at home where I’m finding it brilliant, reliable, intelligent, diligent, glorious, exceptional, and troublesome. Thanks to the mountain team for enabling a good remote-observing session.

The song of the night is Malagueña – Michael Lucarelli, classical guitar:

MAPS Jun. 2025A Night 2: Aligning CACAO

Tonight after some daytime work on the rotator we tried the rotational centering again. Alas Brian saw that the star was still jumping when he sent the command, and thus we still couldn’t find the chief ray. We moved on and attempted a curvature wavefront sensing test where we defocussed the hexapod and that helped us get as close as we could get with alignment.

From last night’s opening:

Next up was CACAO to start improving our AO modes. This took us a while to get set up, especially the IR WFS which we haven’t used for almost a year. By the end of the night we had a 3 modes loop and were attempting to move on but needed more help with the gains gui that was again not working. Tomorrow we’ll keep going!

Here is the MLAT with the IR WFS:

The song of the night is “Diggy Diggy Hole” by Wind Rose: