Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Far Sidelobes from Baffles and Telescope Support Structures in the
  Atacama Cosmology Telescope   The Atacama Cosmology Telescope (ACT) is a 6 m telescope located in the
Atacama Desert, designed to measure the cosmic microwave background (CMB) with
arcminute resolution. ACT, with its third generation polarization sensitive
array, Advanced ACTPol, is being used to measure the anisotropies of the CMB in
five frequency bands in large areas of the sky ($\sim 15,000$ $\rm deg^2$).
These measurements are designed to characterize the large scale structure of
the universe, test cosmological models and constrain the sum of the neutrino
masses. As the sensitivity of these wide surveys increases, the control and
validation of the far sidelobe response becomes increasingly important and is
particularly challenging as multiple reflections, spillover, diffraction and
scattering become difficult to model and characterize at the required levels.
In this work, we present a ray trace model of the ACT upper structure which is
used to describe much of the observed far sidelobe pattern. This model combines
secondary mirror spillover measurements with a 3D CAD model based on
photogrammetry measurements to simulate the beam of the camera and the comoving
ground shield. This simulation shows qualitative agreement with physical optics
tools and features observed in far sidelobe measurements. We present this
method as an efficient first-order calculation that, although it does not
capture all diffraction effects, informs interactions between the structural
components of the telescope and the optical path, which can then be combined
with more computationally intensive physical optics calculations. This method
can be used to predict sidelobe patterns in the design stage of future optical
systems such as the Simons Observatory, CCAT-prime, and CMB Stage IV.

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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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The categories of this paper are: econ