Giant Meterwave Radio Telescope (GMRT), located near Pune in India, is the world's largest radio telescope at metre wavelengths. It is operated by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research, Bombay. An office of NCRA is located in the Pune University campus right next to IUCAA. There are fourteen telescopes randomly arranged in the central square, with a further sixteen arranged in three arms of a "Y"-shaped array (similar to the VLA) giving an interferometric baseline of about 25 km. The GMRT is an interferometer which uses a technique known as aperture_synthesis to make images of radio sources.

Each antenna is 45 metres in diameter and, instead of a solid surface like many radio telescopes, the reflector is made of wire rope stretched between metal struts in a parabolic configuration. This works because of the long wavelengths (21 cm and longer) at which the telescope operates. Each antenna has four different receivers mounted at the focus. Each individual receiver assembly can rotate so that the user can select the frequency at which to observe.

The maximum baseline in the array gives the telescope an angular resolution (the smallest angular scale that can be distinguished) of about 1 arcsecond at the frequency of neutral hydrogen (1420 MHz).

Astronomers from all over the world regularly use this telescope to observe many different astronomical objects such as galaxies, pulsars and supernovae.

Each year on National Science Day the observatory invites the public and pupils from schools and colleges in the surrounding area to visit the site where they can listen to explanations of radio astronomy, receiver technology and astronomy from the engineers and astronomers who work there.

External links

• GMRT Homepage
• Y-shaped array
• Article on Science Day