calibration of the lsst camera andy scacco. lsst basics ground based 8.4m triple mirror design...
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![Page 1: Calibration of the LSST Camera Andy Scacco. LSST Basics Ground based 8.4m triple mirror design Mountaintop in N. Chile Wide 3.5 degree field survey telescope](https://reader036.vdocuments.site/reader036/viewer/2022062722/56649f2a5503460f94c43932/html5/thumbnails/1.jpg)
Calibration of the LSST Camera
Andy Scacco
![Page 2: Calibration of the LSST Camera Andy Scacco. LSST Basics Ground based 8.4m triple mirror design Mountaintop in N. Chile Wide 3.5 degree field survey telescope](https://reader036.vdocuments.site/reader036/viewer/2022062722/56649f2a5503460f94c43932/html5/thumbnails/2.jpg)
LSST Basics
• Ground based
• 8.4m triple mirror design
• Mountaintop in N. Chile
• Wide 3.5 degree field survey telescope
• ~30 Tbits / night of data
• Dark energy / cosmology
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LSST Layout
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Etendue
• Etendue = FOV * Collecting area• Measures the rate of incoming data
0
40
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160
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320
Ete
nd
ue
(m2 d
eg2 )
LSST PS4 PS1 Subaru CFHT SDSS MMT DES 4m VST VISTAIR
SNAPOpt+IR
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The point spread function
• Stars are point sources
• PSF is image of a point source
• Combination of atmosphere + telescope aberration
• Measured by the full width at half maximum (FWHM)
• PSF of LSST has a
30 micron FWHM
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Atmospheric Seeing
• Atmosphere blurs images
• Instrumental blurring is much less than atmosphere
• Large ground based telescopes need adaptive optics
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Camera Design
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Focal Plane CCD Array
• We need a 30 micron spot on focal plane
• CCD wells are 10 x 10 microns
• LSST has 3.2 Gpixels
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Laser
• TEM00 mode
• Helium-neon / Tunable
• Gaussian beam
• Very good for optics analysis
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Monochromator part 1
• Filter / Monochromator
• Pinhole produces Frauenhofer diffraction
• Airy diffraction pattern
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Monochromator part 2
• Airy pattern resembles Gaussian
• Second pinhole cuts off all but the central peak
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Lens aberrations
• Lenses aren’t perfect
• Astigmatism
is biggest
problem for us
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Astigmatism
• Sagittal / tangential rays focus to different locations
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Camera ZEMAX Design
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Spot size as a function of wavelength for a Gaussian beam with an initial waist radius of 15 microns striking the center of the focal plane at an angle
14.5
15
15.5
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17.5
0.000 0.200 0.400 0.600 0.800 1.000 1.200
wavelength in microns
Rad
ius
of
spo
t in
mic
ron
s
0
14
14
19
19
23
23
Azimuthal component
Radial component
Angle in degrees
23°
19°
14°
23°
19°
14°
0°
u g r i z YFilter
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Radial spot size as a function of wavelength for a 15 micron radial waist Gaussian beam pointed at a 0 degree angle from varying distances from the center of the focal plane
14.5
15
15.5
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16.5
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17.5
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18.5
19
0.000 0.200 0.400 0.600 0.800 1.000 1.200
Wavelength in microns
Sp
ot
rad
ius
in m
icro
ns 0
50
100
150
200
250
300
317
Distance from center in mm
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Radial spot size as a function of wavelength for a 15 micron radial waist Gaussian beam pointed at a 0 degree angle from varying distances from the center of the focal plane
14.5
15
15.5
16
16.5
17
17.5
18
18.5
19
0.000 0.200 0.400 0.600 0.800 1.000 1.200
Wavelength in microns
Sp
ot
rad
ius
in m
icro
ns 0
50
100
150
200
250
300
317
Distance from center in mm
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0.384 micron wavelength Gaussian beam at an angle
0
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180
-400 -300 -200 -100 0 100 200 300 400
Distance from center of focal plane in mm
Sp
ot
rad
ius
in m
icro
ns
0
14
19
23.6
14
19
23.6
Angle in degrees
AzimuthalRadial
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0.994 micron wavelength Gaussian beam at an angle
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500
-400 -300 -200 -100 0 100 200 300 400
Distance from center of focal plane in mm
Ra
diu
s o
f s
po
t in
mic
ron
s
0
14
14
19
19
23.6
23.6
Angle in degrees
AzimuthalRadial
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Testing Schematic
Reference
Photodiode Laser
30 micron spot
Photodiode
Array
Focal Plane
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My Other Project…
• Testing a laser sensor system for use in measuring distance very precisely
• It will be accurate enough to be used to measure the flatness of the focal plane of the LSST
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Apparatus
Laser displacement sensors
Optical Flat
Optical FlatPrecision movable platform
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Data
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Data #2
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Further work
• Figure out why the correction function differs between the two trials
• Calculate a best fit sawtooth function to subtract from the data to make it more accurate
• Use the sensor with the correction function to measure the components of the LSST
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Acknowledgements
• David Burke – my excellent mentor
• Andy Rasmussen – other excellent mentor
• Steve Rock
• The DOE, Office of Science
• SLAC
• Stanford
• All my fellow SLAC-ers
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References
http://www.cambridgeincolour.com/tutorials/graphics/airydisk-3D.png
http://navj.wz.cz/061116_025307-70_56_19_226.jpg
http://www.rp-photonics.com/img/gauss_r.png
http://publication.lal.in2p3.fr/2001/web/img344.gif
http://laser.physics.sunysb.edu/~wise/wise187/2005/reports/deb/gauss1.gif
http://cache.eb.com/eb/image?id=3246&rendTypeId=4
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References 2• “Large Synoptic Survey Telescope”, Available at http://www.lsst.org
(2007 August 9).• D. Burke, private communication (2007).• “Point Spread Function”, Available at http://en.wikipedia.org (2007 August
6).• “Astronomical Seeing”, Available at http://en.wikipedia.org (2007 August 3).• “Full Width at Half Maximum”, Available at
http://www.noao.edu/image_gallery/text/fwhm.html (2007 August 6).• “Gaussian Beam”, Available at http://en.wikipedia.org (2007 July 25).• A. Sonnenfeld, private communication (2007). • “Airy Disk”, Available at http://scienceworld.wolfram.com/physics/ (2007 July
25).• “Astigmatism”, Available at http://en.wikipedia.org/wiki/Astigmatism (2007
July 25).• “Aberrations”, Available at http://grus.berkeley.edu/~jrg/Aberrations/ (2007
July 25).