TMS Meeting Minutes, February 2, 2023

Attendees: Andrew, Heejoo, John, Joon, Olga, Trenton (Zoom Meeting)

One LBC Night (last Thursday)
  • 7 channels on each side
  • IQ worse on red side than blue, but reverted after a while
  • Heejoo didn't find any channel combo change during this IQ improvement
  • Likely some other parameters impacting the IQ (will dig into the data)
  • Looking at John's plot on the Dx side, the images taken at high elevation had poor IQ, while the images taken later at low elevation
  • John notes that there was funny stuff going on with TCS at the start of the night (wouldn't worry about the actopt Ry and Rx too much)
  • Thermal focus was out of range on the temperature difference plot
  • Z4 wavefront correction in excess of 6000 nm (Andrew's algorithm)
  • FPIA was run when the target was changed but a new TMS reference was not taken (MISTAKE)
  • If reference had been taken, we could have corrected thermal coma and correctly fixed thermal spherical
  • Suggestion to include a notice to the telescope operator to run a TMS reference when FPIA is run upon acquiring a new target
  • Sx side has similar performance over the course of the whole night
  • Olga notes that the observer that the image quality on the red side went bad two separate times, which was noted in the log
  • This behavior has been seen before, where red drifts away
  • There may be some uncorrected spherical aberration that creeps in on the OB
  • John notes that the red IQ seeing went from 1 to 2" FWHM/seeing @ zenith
  • Olga sent around pupil images because she was wondering how bad they looked
  • Est. seeing on the blue side is greater than the spherical correction threshold, so no spherical correction was applied
  • Initially, large corrections on spherical on the red side, which is consistent with the big temperature swings on red
  • 20230127.023606, big correction applied on red
  • 20230127.00827 also had significant corrections
  • Each FPIA run is making quite a big focus change
  • Also some significant coma, and the pupil images looked comatic to Olga
  • Heejoo notes that we would really like to have an automatic TMS reference taken upon FPIA runs, or at least a notification prompting the telescope operator to take a reference
  • Andrew notes that this data provides strong motivation to improve thermal

Power Outage Last Weekend
  • We may have more channels missing if the mirror was dropped hard on the hardpoints
  • Heejoo will look at the TMS signal tomorrow morning to see if we lost channels
  • Since we only have 7 channels on each side, we may need to ask for realignment
  • Heejoo will send out an update after checking alignment

Pointing
  • John notes that we currently have a Gregorian pointing model (not constructed with TMS)
  • Andrew remarks that the TMS pointing model should be better than the Gregorian pointing model
  • John made a comment that the pointing while using TMS has been okay, which likely means the pointing model is okay
  • However, Olga reminds us that there is an issue with the copointing, where large copointing corrections are needed at times
  • Andrew thinks it would be really useful to compare a pointing model made with TMS versus a pointing model made without TMS
  • Olga confirms that the current pointing model used on LBC is very old and does not use TMS

Engineering Night Tomorrow
(There are 3 half-nights of engineering coming up, 2/1, 2/2, 2/3 MST)
(We are sharing one half night)
  • Night center is ~30 minutes after midnight
  • Olga thinks we have about 3 hours of time available
  • We should have the second half tomorrow night
  • If weather cooperates, there may be some time for TMS testing
  • Olga suggested a couple of items for the testing based on what we discussed, particularly surrounding thermal
  • Channel dropping tests: not going to send corrections during exposure
    • Would like to test channel dropping on sky with TMS updates during exposures (has been done closed dome but not on sky)
    • Would be good to do high and low elevation runs
    • No changing filter, no dithering, just longer exposures while dropping channels
    • Possibly 30 to 60 second exposures (as long as you can without the moon screwing things up)
  • Thermal aberrations (may not work with the other tasks that are scheduled for the night)
    • Two recent science nights provided some good datatsets (red IQ drifts on 1/27)
    • Andrew would like sit near somewhere circumpolar, drive in thermals in the mirror, and run TMS continuously with a defocused mirror (similar to vfast extra) by applying a global -800 micron offset in Z (and possibly along with small offsets in Z11, Z4)
    • Olga has a script on robs to do this sort of thing
    • Olga notes that the last time we did this, the mirror temperature wasn't changing
    • There are limits to how quickly you can change the temperature of the mirror
    • Andrew was able to get a whole sine curve with a 2 deg C amplitude over a whole night
    • Andrew feels that we could probably get half a sine curve over the course of measurement (would take half a night)
    • Defocussed, obtaining pupil information, on a field where elevation doesn't change much (a bit up in altitude from the pole)
    • Bad seeing would make the thermal test a bit useless, but wouldn't care too much about clouds because breaks in sampling would be okay
    • Shouldn't do this test if the seeing is much higher than 1.4 arcsec
    • Once you start scaling FPIA with bad seeing, it reduces the usefulness of the test
  • We will determine at the start of the engineering time which test we will run, based on the seeing
  • We should prepare two scripts, one for channel dropping at low elevation; the other for thermal aberration at high aberration

TMS Journal Publication
  • Trenton will be sending out a draft of the TMS journal publication he is currently writing for everyone to look over and comment on
Trenton to hand off responsibilities to Joon!

Heejoo recommends practicing a laser tracker survey run in the lab (will be borrowing LBTO laser tracker)

-- TrentonBrendel - 02 Feb 2023
Topic revision: r1 - 02 Feb 2023, TrentonBrendel
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