Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Laser Frequency Comb System for Absolute Calibration of the VTT
  Echelle Spectrograph   A wavelength calibration system based on a laser frequency comb (LFC) was
developed in a co-operation between the Kiepenheuer-Institut f\"ur
Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut f\"ur Quantenoptik,
Garching, Germany for permanent installation at the German Vacuum Tower
Telescope (VTT) on Tenerife, Canary Islands. The system was installed
successfully in October 2011. By simultaneously recording the spectra from the
Sun and the LFC, for each exposure a calibration curve can be derived from the
known frequencies of the comb modes that is suitable for absolute calibration
at the meters per second level. We briefly summarize some topics in solar
physics that benefit from absolute spectroscopy and point out the advantages of
LFC compared to traditional calibration techniques. We also sketch the basic
setup of the VTT calibration system and its integration with the existing
echelle spectrograph.

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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci
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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: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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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: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: mtrl-th