EPIC MediumScale Optical Design

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EPIC Medium-Scale Optical Design

• Huan Tran
• Brad Johnson
• Mark Dragovan
• April 2009

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EPIC-IM optical layout
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EPIC-IM optical properties

• Crossed Dragone
• ABS, Clover, QUIXOTE, QUIET .
• Unprecedented Large FOV
• 30x20 degrees
• Extreme Compact design
• Maximize resolution/throughput in shroud
• Telecentric
• NO refractive elements

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EPIC-IM optical properties
Oversize mirrors
force telecentric focal plane gt cold aperture
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EPIC-IM aberration performance

• Elliptical focal plane
• Limited by vignetting in Y
• Limited by aberration in X
• Multiband
• High Frequencies in center
• 30800 GHz
• 11,000 bolometers

850 GHz
30 GHz
30 deg/ 160 cm
30 GHz
150 GHz
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EPIC-IM cold vs warm
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Main Beam Simulations

• Beam shapes
• No Refracting elements
• Calculated with Perfect Gaussian Feed horns
• Calculated for each Hex
• Polarized beam-scale distortions
• Fit Gaussians to beams
• Compare to benchmarks

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PO co and crosspolbeams for single feed
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PO vs GO sanity check
30 GHz beam, from Grasp 9
Spot diagram, from Zemax
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Main beam effects vs benchmark
EPIC-IM mirrors alone are below benchmarks w/o
modulation
Fig. 6.4 Histograms of main beam effects. Refer
to Section 5.4.1 for definitions of each effect.
Histograms are color coded by frequency. Colored
Arrows denote the frequency dependant goals from
table 5.4. Goals for some
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Sidelobes

• Analyzed with Physical Optics(PO) an Geometric
  Theory of Diffraction (GTD)
• Aperture Integration Method
• Optics box
• Galaxy Convolution

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EPIC-IM straylight

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EPIC-IM farsidelobes
Co-pol beam, no baffling
15d simulation time
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Aperture Integration method
Set J 0 outside

Calculate Equiv J
28d sim time
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Polarized Far Sidelobes
(QT2 UT2 VT2)1/2
2 x15d sim time
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Galactic Contamination

• In order to evaluate the effect of the signal
  from the far sidelobes, we convolve the qt beam
  maps with a 150 GHz sky model.
• The beam patterns have the primary beam masked,
  so only the response to the sidelobes are evident
  in the output.
• The sky data is an all sky map at long
  wavelengths (150 GHz).
• Since the beam is asymmetric, it is necessary to
  rotate the beam with respect to the sky at each
  point to get the complete convolution.
• The convolutions were done using the
  totalconvolver code developed by the Planck
  community. (Gorski et. al.)

M.Dragovan
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(above) The 150 GHz sky map with which the
beams are convolved. Units are log(uK). (below)
The results of the convolution, qt beam with
the above sky . Units are (uK).
M.Dragovan
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In order to further quantify this result, we make
two histograms the number of pixels with a
given intensity (left plot), and the integrated
histogram giving the total number of pixels less
than a given intensity (right plot). This is
similar to the plots that are shown for site
surveys.
Goal 1nK
By inspection one can see that fully 90 of the
pixels are lt0.2nK.
M.Dragovan
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GTD and Polarization of sidelobes

• Our Far sidelobe simulations were for 3.25 f l,
  but

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Conclusions

• EPIC-IM has enormous throughput
• Systematic beam effects are below benchmark
• Sidelobes are manageable
• More analysis time required to be sure