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Gauribidanur Low Frequency Array
 
This decametrewave telescope at Gauribidanur, about 100 km from Bangalore, is operated as a collaboration between the Raman Research Institute and the Indian Institute of Astrophysics.

Operating at 34.5 MHz, it is essentially a meridian-transit instrument with some amount of tracking capability. The telescope consists of 1000 fat dipoles arranged in the form of the letter 'T'. The dipole orientation being along the east-west direction the instrument is sensitive to only the east-west component of the polarization. The usable bandwidth is about 10 MHz centred at 32 MHz, while the maximum available effective collecting area is about 18000 square metres.


The array beams can be steered by appropriately phasing their elements. The beam of the N-S arm can be tilted within a declination range -45° to 75°. The beam of the E-W array can be tilted similarly in hour-angle within 10° around the meridian enabling tracking for a minimum of 42 minutes.

The mean sky brightness temperature at this frequency is about 10,000 K and so the minimum detectable flux density for a point source is about 10 Jy with an integration time of 10 s and a bandwidth of 200 kHz. This telescope has been used for continuum surveys of the accessible sky, studies of supernova remnants, giant HII regions, as well as of radio emissions from the undisturbed sun and solar bursts. Using the tracking facility, observations of low-frequency radio recombination lines and emission from many nearby pulsars have been made.
 
 
Mauritius radio telescope
 
 
The Mauritius Radio Telescope (MRT) is a Fourier synthesis array, constructed and operated collaboratively by the Raman Research Institute, Indian Institute of Astrophysics, and the University of Mauritius. The telescope is situated at Bras d'Eau, in the north-east of Mauritius, an island in the Indian Ocean.

The telescope is a T-shaped non-coplanar array, consisting of 2048 m long East-West (EW) arm and an 880 m long South arm. In the EW arm 1024 helices are arranged in 32 groups; in the south arm, 16 trolleys with 4 helices each that move on a rail are used for synthesis.

A 512 channel, 2-bit 3-level complex correlation receiver is used to measure visibilities. At least 60 days of observations are required for obtaining the visibilities up to 880 m spacing. After calibration, the visibilities are transformed to adjust for the non-coplanarity of the array and to produce an image of the area of the sky under observation.


 
 
 
 
 
   
 
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