Transcript LBC-Blue pre-commissioning runs

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
Opto-mechanical Design
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)
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…
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
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
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
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.
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
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)