Calibration of the LSST Camera

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Calibration of the LSST Camera

• Andy Scacco

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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

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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 arent 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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Testing Schematic
Reference Photodiode
Photodiode Array
Laser
Focal Plane
30 micron spot
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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
Optical Flat
Precision movable platform
Laser displacement sensors
Optical Flat
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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//navj.wz.cz/061116_025307-70_56_19_226.jpg
http//www.cambridgeincolour.com/tutorials/graphic
s/airydisk-3D.png
http//www.rp-photonics.com/img/gauss_r.png
http//publication.lal.in2p3.fr/2001/web/img344.gi
f
http//laser.physics.sunysb.edu/wise/wise187/2005
/reports/deb/gauss1.gif
http//cache.eb.com/eb/image?id3246rendTypeId4
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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.wolf
  ram.com/physics/ (2007 July 25).
• Astigmatism, Available at http//en.wikipedia.or
  g/wiki/Astigmatism (2007 July 25).
• Aberrations, Available at http//grus.berkeley.e
  du/jrg/Aberrations/ (2007 July 25).