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Calibration of the LSST Camera

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Camera Design. Focal Plane CCD Array. We need a 30 micron spot on focal plane ... Lens aberrations. Lenses aren't perfect. Astigmatism. is biggest. problem for ... – PowerPoint PPT presentation

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Title: Calibration of the LSST Camera


1
Calibration of the LSST Camera
  • Andy Scacco

2
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

3
LSST Layout
4
Etendue
  • Etendue FOV Collecting area
  • Measures the rate of incoming data

5
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

6
Atmospheric Seeing
  • Atmosphere blurs images
  • Instrumental blurring is much less than
    atmosphere
  • Large ground based telescopes need adaptive optics

7
Camera Design
8
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

9
Laser
  • TEM00 mode
  • Helium-neon / Tunable
  • Gaussian beam
  • Very good for optics analysis

10
Monochromator part 1
  • Filter / Monochromator
  • Pinhole produces Frauenhofer diffraction
  • Airy diffraction pattern

11
Monochromator part 2
  • Airy pattern resembles Gaussian
  • Second pinhole cuts off all but the central peak

12
Lens aberrations
  • Lenses arent perfect
  • Astigmatism
  • is biggest
  • problem for us

13
Astigmatism
  • Sagittal / tangential rays focus to different
    locations

14
Camera ZEMAX Design
15
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20
Testing Schematic
Reference Photodiode
Photodiode Array
Laser
Focal Plane
30 micron spot
21
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

22
Apparatus
Optical Flat
Precision movable platform
Laser displacement sensors
Optical Flat
23
Data
24
Data 2
25
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

26
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

27
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
28
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).
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