Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The AstroSat Mass Model: Imaging and Flux studies of off-axis sources
  with CZTI   The Cadmium Zinc Telluride Imager (CZTI) on AstroSat is a hard X-ray
coded-aperture mask instrument with a primary field of view of 4.6 x 4.6
degrees (FWHM). The instrument collimators become increasingly transparent at
energies above $\sim$100 keV, making CZTI sensitive to radiation from the
entire sky. While this has enabled CZTI to detect a large number of off-axis
transient sources, calculating the source flux or spectrum requires knowledge
of the direction and energy dependent attenuation of the radiation incident
upon the detector. Here, we present a GEANT4-based mass model of CZTI and
AstroSat that can be used to simulate the satellite response to the incident
radiation, and to calculate an effective "response file" for converting the
source counts into fluxes and spectra. We provide details of the geometry and
interaction physics, and validate the model by comparing the simulations of
imaging and flux studies with observations. Spectroscopic validation of the
mass model is discussed in a companion paper, Chattopadhyay 2021.

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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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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: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: cs
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex