Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Astrometric Foundation of Astrophysics   Astrophysical studies require a knowledge of very accurate positions, motions
and distances of stars. A brief overview is given of the significance and
development of astrometry by ESA's two astrometric satellites, Hipparcos and
Gaia, launched in respectively 1989 and 2013. The astrometric foundation of all
branches of astronomy from the solar system and stellar systems to compact
galaxies, quasars and dark matter is being revolutionized by the observations
from these satellites. The future of fundamental astrometry must be considered
in a time frame of 50 years, therefore science issues for a Gaia successor
mission in twenty years are discussed in an extensive report: "Absolute
astrometry in the next 50 years" available at http://arxiv.org/abs/1408.2190

19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol