Giant metrewave radio telescope - its possible use for SETI

Abstract

A Giant Metrewave Radio Telescope (GMRT) is being set up at Khodad, about 80 km north of Pune in India, to study a wide range of outstanding problems in modern astronomy such as those concerning pulsars, quasars, radio galaxies and the origin and evolution of the Universe. GMRT will consist of 34 fully-steerable parabolic dishes of 45 m diameter each. A novel design has been adopted for the dishes which uses rope trusses placed between 16 parabolic frames to support the reflecting surface. Sixteen of these would be placed in a compact central array of about 1 × 1 km² in size, including nine forming a 3 × 3 grating to facilitate deep searches for new pulsars. The other 18 antennas will be placed along the arms of a Y-shaped array with each arm extending to about 14 km. GMRT is being designed to operate in six different frequency bands between 38 and 1420 MHz. The reflecting surface of the dishes will be made of stainless steel wires of 0.55 mm diameter. The size of the mesh in the central part will be 10 × 10 mm, in the middle 15 × 15 mm and in the outer part it is 20 × 20 mm. A 512 channel FFT unit with a bandwidth of 16 MHz placed at each antenna followed by a complex correlator (FX system) is planned to cross correlate outputs of all the 34 antennas for both polarizations. This is advantageous for spectral line observations and also for rejection of considerable RF interference expected at metre wavelengths. The total effective area of GMRT will be about 27,000 m² at 1420 MHz, nearly the same as for the Arcebo Radio Telescope, but GMRT has a much wider declination range and less radio interference suceptibility. Hence, GMRT will be extremely valuable for the Search for Extraterrestrial Intelligence (SETI). The possible use of GMRT for SETI is described in this paper. It is suggested that the GMRT antenna design may be used for a low-cost 1000 element SETI Array (EISA) as an international endeavour.