Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Techniques of Radio Astronomy   This chapter provides an overview of the techniques of radio astronomy. This
study began in 1931 with Jansky's discovery of emission from the cosmos, but
the period of rapid progress began fifteen years later. From then to the
present, the wavelength range expanded from a few meters to the
sub-millimeters, the angular resolution increased from degrees to finer than
milli arc seconds and the receiver sensitivities have improved by large
factors. Today, the technique of aperture synthesis produces images comparable
to or exceeding those obtained with the best optical facilities. In addition to
technical advances, the scientific discoveries made in the radio range have
contributed much to opening new visions of our universe. There are numerous
national radio facilities spread over the world. In the near future, a new era
of truly global radio observatories will begin. This chapter contains a short
history of the development of the field, details of calibration procedures,
coherent/heterodyne and incoherent/bolometer receiver systems, observing
methods for single apertures and interferometers, and an overview of aperture
synthesis.

15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
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The categories of this paper are: nlin
14
The categories of this paper are: math-ph