Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Characterization and Status of a Terahertz Telescope   The Receiver Lab Telescope (RLT) is a ground-based terahertz observatory,
located at an altitude of 5525 m on Cerro Sairecabur, Chile. The RLT has been
in operation since late 2002, producing the first well-calibrated astronomical
data from the ground at frequencies above 1 THz. We discuss the status of this
telescope after 18 months of operation and plans for the upcoming observing
season.
  There are many practical challenges to operating a telescope at these
frequencies, including difficulties in determining the pointing, measuring the
telescope beam and efficiency, and calibrating data, resulting from high
receiver noise, receiver gain instabilities, and low atmospheric transmission.
We present some of the techniques we have employed for the RLT, including the
use of atmospheric absorption lines in the place of continuum measurements for
efficiency and beam measurements, and the utility of a Fourier-transform
spectrometer for producing reliable data calibration.

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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc