TMS Meeting Minutes, November 19, 2020

Attendees: Andrew, Breann, Heejoo, John, Trenton, Matthieu, Yang (Zoom Meeting)

Meeting Notes:

Summary from Past Week
  • 11 hours passive TMS run yesterday with NO ISSUES!
  • Heejoo working to vizualize data
  • Taking telescope data from TCS elevation, telemetry, and plotting with TMS data
  • Andrew noted some jumpiness on the TMS channels data
  • Suspects wind gust on the primary mirror (buffeting)
  • Didn't happen on channels across the mirror, but the channels above the mirror
  • Andrew would like to see time-stamped animometer data
  • Curious to see if there's more chop when we are looking into the wind on the primary mirror
  • Andrew would like to work with Yang on the ch dropping variation we're seeing
  • Are we getting divergence from the very stable eTalon data we are seeing vs. Yang's code?
  • Andrew planning to use a variety of different Jacobians with eTalon data
  • Andrew asks Yang to do the same process with his code; will send Yang Mathematica notebook with the Jacobians he's using
  • We need to understand this jumping that we are seeing with continuous dropping of channels

  • Andrew points out that the first time we ran TMS with channel dropping, we saw jumps after about an hour with continuous ch dropping applied
  • The proposed analysis will help us understand what was happening with this failure
  • Yang suggests that what is needed for validation is an enhanced error-checking and channel filtering methodology
  • The current filter is too simple
  • Andrew wants to push ahead with getting on sky, controlling the telescope and collecting LBCr images
  • We have not yet controlled the telescope while collecting on sky images and run TMS

  • By next week, Andrew to describe what we would like to do on-sky to move towards validation/commissioning

Andrew's Paper: A laser-truss-based optical alignment system on LBT.
  • TMS team to contribute to Andrew's publication by providing suggestions
  • Andrew asking Yang to provide recommendations for software section
  • Deadline: November 25th (per Andrew's request)
  • Page Length Limit (SPIE) is 20 single-sided pages
  • Please send a .docx file with changes tracked
  • Andrew mentions a pure degeneracy between shape and position, which may be very interesting when applied to AOM (Active Optics Metrology) on the GMT

Heejoo's Questions RE: Data Processing
  • Planning to take pose data at certain time for each object, as this is likely to have the best
  • REMINDER from John: Need to use the start time that's in the FITS file header, NOT the time of modification
  • Will be interesting to see if there is a correlation between FWHM and comatic ellipticity with TMS results
  • TMS should predict coma and focus, so it will be great to see if LBCr and TMS

IQ from Last Night (Christian)
  • Christian showed results from last night on LBCb and LBCr
  • Focus images shown; generally changes made when going to a new target, but if things degrade quickly, focus is reacquired
  • Nice, sub-arcsec seeing images, meaning you can use ellipticities on the focal plane to pull out information
  • High peak noted at lbcr.20201119.051229 on just one side
  • Andrew asked Christian to make a copy of the blue/red/focus LBC IQ plot with seeing included
  • Seeing degraded over the night
  • IQ better on the blue side towards start... which is weird
  • Red should generally be better than blue
  • Once the seeing went bad, the images were actually better than the seeing indicated
  • Would be interesting to see an overlay of TMS data to see predictions from decenters and focus terms; interesting to see if correlation between DZ's on TMS and the degradation of IQ
  • Christian to provide a four by grid with IQ, ellipticity, FWHM, etc
  • Andrew: Is there an easy way to distinguish between ellipticity and astigmatism?
  • To really differentiate between astigmatism signal and coma signal, need to do some pixel photometry (suggests using IRAF tool)

Ciddor Correction
  • Trenton's MATLAB and Yang's Python Ciddor corrections give the same results
  • Andrew suggests we should compare the Ciddor correction to the eTalon system (which uses a default temp of 20 C for vacuum correction)
  • With same pressure and humidity, as well, which is included on the XLS file
  • Use the eTalon temp telemetry

EO Collimator Lens Barrel/Lens
  • Heejoo suggests using EO or ThorLabs lens barrel (look for similar file)
  • Also, could use URIC to fabricate lens barrels, if needed (cost about $800-$1000 dollar to prototype 2-3 barrels)
  • Andrew to talk to Chinese fabricator to make his collimators with their glass and manufacturers
  • Heejoo suggests purchasing a 1550 nm source
  • Andrew suggests using 633 nm interferometer with a double pass source to focus the collimator
  • If we want to null the fiber collimator
  • Andrew suggests using Shack-Hartmann with 633 nm for alignment
  • Right now, Trenton designing with a 25 mm lens... however, Andrew's collimator designing uses a 15 mm diameter
  • With the 15 mm collimator, compared to the 7 mm collimator, doesn't make the
  • Trenton suggests comparing the 25 mm diam. collimator to the 15 mm diam. collimator, to the 7.5 mm diam.
  • Beam walk tolerance on retro-reflectors to collimators is interesting problem for a student at the UofA

Regarding Focus Diversity Applied to FPIA
  • Trenton to be connected with Subasa by Andrew
  • Trenton has been doing lots of reading of references

About Running Yang's Code w/o Yang Present
  • Yang to provide some shortcuts to allow Andrew and Heejoo to run Yang's code
  • Andrew and Heejoo would like to be able to test the TCP/IP dropping fault on their own

  • Heejoo will share about any change to do an engineering run with TMS
  • Andrew would like to be able to run Yang's code and try to recreate the TCP/IP fault
  • Remember to provide Andrew with feedback on the paper this week!
-- TrentonBrendel - 19 Nov 2020
Topic revision: r1 - 20 Nov 2020, TrentonBrendel
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