With 30 antennas and a maximum baseline length of 25 km , the Giant Metrewave Radio Telescope ( GMRT ) is the premier low-frequency radio interferometer today .
We have carried out a study of possible expansions of the GMRT , via adding new antennas and installing focal plane arrays ( FPAs ) , to improve its point-source sensitivity , surface brightness sensitivity , angular resolution , field of view , and U-V coverage .
We have carried out array configuration studies , aimed at minimizing the number of new GMRT antennas required to obtain a well-behaved synthesized beam over a wide range of angular resolutions for full-synthesis observations .
This was done via two approaches , tomographic projection and random sampling , to identify the optimal locations for the new GMRT antennas .
We report results for the optimal locations of the antennas of an expanded array ( the “ EGMRT ” ) , consisting of the existing 30 GMRT antennas , 30 new antennas at short distances , \lesssim 2.5 km from the GMRT array centre , and 26 additional antennas at relatively long distances , \approx 5 - 25 km from the array centre .
The collecting area and the field of view of the proposed EGMRT array would be larger by factors of , respectively , \approx 3 and \approx 30 , than those of the GMRT .
Indeed , the EGMRT continuum sensitivity and survey speed with 550 - 850 MHz FPAs installed on the 45 antennas within a distance of \approx 2.5 km of the array centre would be far better than those of any existing interferometer , and comparable to the sensitivity and survey speed of Phase-1 of the Square Kilometre Array .