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LBC-Blue pre-commissioning

This document outlines the pre-commissioning activities for the LBC-Blue camera, detailing observation preparation and execution from May to October 2023. Key developments include improvements in opto-mechanical design, filter specifications, and image analysis algorithms. The report highlights two pre-commissioning runs, addressing technical challenges such as focal plane tilt and guiding systems. Preparations for the commissioning phase set to begin on October 23 are also discussed, emphasizing automation in observation management and quality assessment through innovative algorithms.

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LBC-Blue pre-commissioning

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  1. LBC-Blue pre-commissioning • LBC-Blue • E Giallongo (PI) • Rome: diPaola, Pedichini, Speziali, Testa, Gallozzi • Arcetri/Padova/Bologna: Ragazzoni (co-PI), Barufollo, Diolaiti • Trieste: Smareglia, Gasparo • field of view, filters • taking data: preparing & executing the observations • Two pre-commissioning runs this year: • Summer (May – mid-July) • Fall (mid-Sept to present) leading up to LBC-Blue commissioning late October

  2. Opto-mechanical Design

  3. LBC-Blue: focal plane • 4 2048 x 4608 pix ‘science’ chips • 0.23”/pxl (7.85’ x 17.7’ per chip) • separated by 80 pxl (18”) gaps • ~ 27’ x 27’ field of view • 2 512 x 2048 pix ‘technical’ chips • first 256 lines masked to be used without shutter (~frame transfer CCDs) • fast readout: 1.2s for the 256x2048 area • 1’ x 7.85’ field of view • for guiding & active optics • all behind shutter & filter from “LBC Blue Channel: The CCD Camera” (Giallongo (PI), Speziali, diPaola, Pedichini , Ragazzoni (co-PI)& LBC team)

  4. Wavelength coverage • Filters intended (8/channel at one time) • LBC-Blue: • Bessel U,B,V • Sloan g’, r’ (u’ to be added) • LBC-Red: • Bessel V, R, mod-I • Sloan r’,z’ (i’ to be added) • NB 910nm/30nm fwhm (under consideration) • Sensitivities • ETC gives 5s-1hr for 0.9” seeing, 1.8” SW aperture, no moon, airmass = 1.3: • B~27.1, U~25.4, V~26.9 • First light image at B consistent with estimate from ETC. • Estimates only! to be measured during commissioning…

  5. Preparing Observing Blocks • OB tool runs on Linux & Windows (Gallozzi) • set pointing, position angle • configure Blue & Red channel: dither pattern, exposure time, Nexp • Writes out xml file

  6. Executing Observing Blocks • LBC Control SW: • Runs from firefox browser • Uploads OB • Executes observation • Interfaces with TCS: slews, obtains rotator trajectory, dithers • Guiding for exposures longer than a given threshold (~30sec) • Technical chip exposures 2,4,8,…sec taken • Automatically searched for stars; when sufficient stars found, starts guiding

  7. Focus & Collimation • Slew to target • Execute OB to move M1 down by 0.8mm (60pxl pupil) • Obtain 15-20s image using a ~1000 line window of chip 2 • Analyze with IDL algorithm (Barufollo & Ragazzoni): • Automatically finds bright isolated pupils • computes Zernike coefficients • sends the results to the TCS/PSF which adjusts mirror position & forces • 2-3 iterations to achieve focus & collimation • Frequency of focus/collimation? TBD, depends on accuracy of collimation lookup table

  8. Summer (May to mid-July) pre-commissioning • CCD Controllers (Pedichini, Skytech) • Returned from Rome/Skytech • Source of pickup noise tracked down and eliminated • Decreased image transfer time (diPaola & Smareglia) • 105s total: • 26 s readout (41 s readout & demultiplexing) • transfer from LBC CMU to archive and from • LBC archive to user machine • Development of single extra-focal image analysis algorithm (Barufollo & Ragazzoni) • MAT (4” rms) and LBC (7.6” rms) pointing models • First collimation lookup table made • Mirror position (x,y,z,rx,ry) vs elevation for about a dozen datapoints. • Outstanding Issues in mid-July: • rotator cable chain buckling • Focal plane tilt (100 microns) which had existed since fall 2005.

  9. Fall (Sept – late Oct) pre-commissioning • New rotator cable chain installed • Fixed focal plane tilt • Shimmed rotator flange by 0.38mm • Guiding works • Tasks for the next two weekends: • Refinement of collimation lookup table • Refinement of pointing models (MAT and LBC) • Refinement of active optics code (Oct 19-22) • LBC-Blue Commissioning to begin October 23

  10. Quantum Efficiencies from Pedichini F., Speziali, R., Diolaiti, E., Ragazzoni, R. 2002, “The Large Binocular Camera of LBT: The focal plane detectors”, http://lbc.mporzio.astro.it/Documentation/The_Detectors.pdf (in later document, one blue chip differs; QE for this one 1-8% lower but similar shape)

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