TMS Meeting Minutes, May 12, 2022

Attendees: Andrew, Christian, Heejoo, John, Olga, Yang (Zoom Meeting)
  • Trenton was unable to attend as he was busy at the Optical Sciences Commencement Ceremony receiving his Masters degree and celebrating other graduates from LOFT
Two LBC Nights, 5/6 and 5/7
  • Jennifer gave a glowing review of TMS, indicating that she felt that the collimation downtime was greatly reduced with TMS running
  • Heejoo noticed unfamiliar trends in large corrections in Group Y and Tilt X, which continued for two days; though the images were nice, the trend is a bit odd
  • It turns out that this is something we shouldn't be concerned about
  • There is a certain tilting to the hub, which allows a rotation of the primary around the coma-neutral point, which shows up as Y and Rx on the TMS
  • Interesting inflection on the left side around 7 UT in Ry
  • Is it possible that our pointing correction is fighting the guider? - John
  • Andrew remarks that we should strongly consider using the TMS collimation model which was generated four years ago, according to John, but never implemented, maybe
  • For the most recent data set that was taken about 4 months ago, a new TMS pointing model was never constructed; this is on Olga's list of things to do
  • John cautions the team that we need to be very careful when implementing new pointing models, as we can't afford to break other instrument configurations with our setup
Drift Observed when Tracking Field through High Elevation
  • Olga is curious about the behavior of the system while tracking a field through high elevation and through transit as observed during the engineering night on April 18th (red only)
  • Olga repeated this on 5/05 with both LBC, but saw a much smaller drift than observed on 4/18
  • Andrew has convinced himself that, given that we do see thermal coma, we will absolutely see thermal tilt, which is a completely uncontrolled mode
  • Andrew plans to spend more of his bandwidth working on decomposing higher order thermal shape on the mirror using his Mathematica model
  • "The biggest game of whack-a-mole in the world" - Andrew
  • Olga notes it is quite difficult to drive in the thermal changes needed when the mirrors are in good thermal equilibrium
  • John has added a new option to his beautiful plots which shows all channel dropping including which channels drops
  • Heejoo plans to go back and re-plot some our data that included jumps to see if channel dropping was the cause
20220506 Data
  • There appears to be some differences where the left side only starts correcting Y and Rx at 4 UT while the right side corrects right from the start
  • Andrew mentions that there could be a way that we could suss out the differences in Y and Rx in terms of structural deflections, we would need to subtract out the elevation dependence
  • John notes that the two sides are really not in similar thermal environments, as wind could blow over one mirror
  • Olga clarifies that if we were not using TMS, we would see a lot of error building up in the Y motion, up to about 250 microns over 6 hours
  • Even if TMS weren't running, there would be still be some correction to Y and Rx, but we are measuring the errors relative to the pointing model and the collimation model
  • Allowing the guiding corrections to come through, so the guiding corrections take care of the pointing model (no differential pointing model, b/c the pointing model is the same on both sides)
  • TMS is correcting errors to make the primary look like it's not moving with respect to the hub, so bogus corrections from the pointing model w.r.t. elevation can be corrected out
Channel Dropping (Yang's Detailed Email)
  • Might be better to discuss it by email (responses may take an hour or more to compose)
  • Team will continue working on this via email
Channel Dropping Test During Engineering
  • Andrew suggests that we should consider testing this during the day at Zenith
  • Heejoo notes that the softare has already successfully passed this test
  • John states that the problem is that the algorithm works fine when the telescope is sitting stationary but it does not work when the telescope is moving around
  • John thinks that it should be a very simple fix
  • Olga lists the upcoming engineering nights:
    • 5/28
    • 6/6
    • 6/7
    • 6/16
    • 7/3
  • Very few opportunities left this semester
  • Heejoo hopes to have a fully functional code with channel dropping by 5/28
  • Andrew notes that we should also test that TMS can run with focus and spherical corrections by running during the daytime and dropping channels

-- TrentonBrendel - 19 May 2022
Topic revision: r1 - 20 May 2022, TrentonBrendel
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