Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: RadioAstron -- a Telescope with a Size of 300 000 km: Main Parameters
  and First Observational Results   The Russian Academy of Sciences and Federal Space Agency, together with the
participation of many international organizations, worked toward the launch of
the RadioAstron orbiting space observatory with its onboard 10-m reflector
radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with
some of the largest ground-based radio telescopes and a set of stations for
tracking, collecting, and reducing the data obtained, this space radio
telescope forms a multi-antenna ground-space radio interferometer with
extremely long baselines, making it possible for the first time to study
various objects in the Universe with angular resolutions a million times better
than is possible with the human eye. The project is targeted at systematic
studies of compact radio-emitting sources and their dynamics. Objects to be
studied include supermassive black holes, accretion disks, and relativistic
jets in active galactic nuclei, stellar-mass black holes, neutron stars and
hypothetical quark stars, regions of formation of stars and planetary systems
in our and other galaxies, interplanetary and interstellar plasma, and the
gravitational field of the Earth. The results of ground-based and inflight
tests of the space radio telescope carried out in both autonomous and
ground-space interferometric regimes are reported. The derived characteristics
are in agreement with the main requirements of the project. The astrophysical
science program has begun.

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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: hep-th
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin