Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 4GREAT -- a four-color receiver for high-resolution airborne terahertz
  spectroscopy   4GREAT is an extension of the German Receiver for Astronomy at Terahertz
frequencies (GREAT) operated aboard the Stratospheric Observatory for Infrared
Astronomy (SOFIA). The spectrometer comprises four different detector bands and
their associated subsystems for simultaneous and fully independent science
operation. All detector beams are co-aligned on the sky. The frequency bands of
4GREAT cover 491-635, 890-1090, 1240-1525 and 2490-2590 GHz, respectively. This
paper presents the design and characterization of the instrument, and its
in-flight performance. 4GREAT saw first light in June 2018, and has been
offered to the interested SOFIA communities starting with observing cycle 6.

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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
4
The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org