By Tata Institute of Fundamental Research
National Centre for Radio Astrophysics
The Giant Metrewave Radio Telescope, or the GMRT is a unique telescope facility proposed and set up by National Centre for Radio Astrophysics. It is the most sensitive radio telescope in the world in the 30-1500 MHz frequency range and a very versatile instrument for investigating a variety of radio astrophysical problems ranging from nearby Solar system to the edge of observable Universe. GMRT is one of the most challenging experimental programmes in basic sciences undertaken by Indian Scientists and Engineers. This is the story of how the telescope was built.
Ooty Radio Telescope - group photograph by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research
The radio astronomy group of TIFR led by Govind Swarup constructed the Ooty radio Telescope between 1965-1970 and used it for over a decade to make several pioneering discoveries in radio astronomy. By the early 1980s the group began to think about an even larger project.
Govind Swarup in NigeriaTata Institute of Fundamental Research
Ideas began to develop within the group for a Giant Equatorial Radio Telescope - a cylindrical design like the Ooty Telescope but much larger - 2 km long and 50 m wide - to be placed at a suitable site in either Kenya or Indonesia.
UNESCO supported this effort and arranged for visits by Swarup and others to Kenya, Nigeria, Senegal and Indonesia. But for various reasons this idea fell through.
Prototype Giant Metrewave Radio Telescope dish under constructionTata Institute of Fundamental Research
Swarup then came up with another idea. Instead of one large cylinder, he decided to use several smaller parabolic dishes instead.
They invented a new technique called SMART (Stretched Mesh Attached to Rope Trusses) to build dishes that would allow for the building of large 45 m dishes, quickly and affordably.
A prototype dish was built in Ooty to test the feasibility of all their ideas . They called their new telescope - The Giant Meterwave Radio Telescope (or GMRT for short). It was to become the largest low frequency radio telescope in the world.
Preparing the foundation for a new Giant Metrewave Radio Telescope dish.Tata Institute of Fundamental Research
The government of India approved the GMRT project in 1987.
A suitable site was soon identified near Pune, in India and Swarup and his team set about constructing the telescope
Giant Meterwave Radio Telescope by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research
The challenges were many; both technical and financial hurdles had to be overcome.
On a cement pedestal, a gigantic fork mount made of steel, had to be placed.
Giant Meterwave Radio Telescope by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research
The frame of the dish was then painstakingly put together on the ground.
Giant Meterwave Radio Telescope by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research
Once each dish was assembled on the ground around the concrete base, it would be raised up by human effort using 4 winches.
Giant Metrewave Radio Telescope dish at sunset hoisted up on its pedestalTata Institute of Fundamental Research
Once a dish was raised up and properly mounted on its fork mount, it was time for the team to repeat the process for the next dish. A total of 30 dishes were constructed in this fashion.
A view of the Central Electronics buildingTata Institute of Fundamental Research
The signals from each dish had to be transported by optical fibre to the central electronics building where a great deal of electronic equipment converted the data into a form suitable for the hardware correlator to process. Almost everything was being done in India for the first time.
5 Giant Metrewave Radio Telescope dishes lit up in the twilightTata Institute of Fundamental Research
After more than a decade of relentless efforts by the whole team, the telescope was finally ready.
In 2002, it was released as an international open access facility.
Any astronomer anywhere in the world with a clever idea could propose to use the GMRT for their research.
A view of several Giant Metrewave Radio Telescope dishesTata Institute of Fundamental Research
And indeed many did; astronomers from more than 40 countries in all continents have written proposals to use the GMRT.
It has become one of the most important radio telescopes of the world.
Radio haloes and relics in Planck clusters observed by the Giant Metrewave Radio TelescopeTata Institute of Fundamental Research
Over the last decade and a half, astronomers have used the GMRT to study a number of exotic objects - galaxy clusters, quasars, radio galaxies, pulsars, supernova remnants, star forming regions and many more.
The GMRT telescope is sensitive enough to pick up signals from probes on Mars!
The GMRT data when combined with data from other telescopes has vastly improved our understanding of the Universe
This story is developed by National Centre for Radio Astrophysics, a unit of Tata Institute of Fundamental Research.
Photographs courtesy:
NCRA Archives
Govind Swaup's personal collection
TIFR Archives
For any feedback about this narrative please write to us at ncrapublic@gmail.com
