2004 ASTRONOMY & ASTROPHYSICS - Indian Academy of Sciences

RADIO ASTRONOMY
The first telescope to be built was at Gauribidanur
about 75 km north of Bangalore. This “array”
consists of 1000 dipoles arranged in the form of
the letter “T”, with a 1.4 km long east–west
array and a 0.45 km long southern arm. The
response of this array is steered by suitably
phasing the telescope. At the operating frequency
of 34.5 MHz, this telescope has an angular
resolution of 26’ × 42’ and a collecting area of
18,000 m 2 at zenith.
Radio astronomy at such long wavelengths is a
niche activity in India because in the more
developed countries there is widespread use of
these frequency bands which interferes with
astronomical observations. This instrument was
used to map the visible sky within ±50 degrees of
zenith angle. Given the angular resolution and the
sensitivity of this telescope, this is the best map
made so far at such a low frequency and this
entire survey has now been made available to the
worldwide community of astronomers. Radio
recombination lines from highly excited carbon
The Mauritius Radio Telescope
atoms, as well as several nearby pulsars have been
studied.
In the late 1980s, the groups at the Raman
Research Institute and the Indian Institute of
Astrophysics collaborated with the University of
Mauritius to set up the Mauritius Radio Telescope.
This is an array of helical antennae arranged in an
arm of the order of a kilometre, and operates at a
wavelength of 2 m. A major survey of the southern
sky has been carried out with this telescope.
Again in the late 1980s, the PRL group set up
A map of the sky at 34.5 MHz synthesized with the Gauribidanur array
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