Building the Ooty Radio Telescope

The incredible story of how the world's longest steerable telescope was built in India

By Tata Institute of Fundamental Research

Letter From Homi Bhabha to Govind Swarup (1962-04-03)Tata Institute of Fundamental Research

In April 1963, Govind Swarup returned to India after spending nearly a decade abroad working with the leading radio astronomers of the world. He joined the Tata Institute of Fundamental Research in Mumbai. The Institute’s Director, Homi Bhabha, was looking forward to rapid developments in radio astronomy in India.

Here's the original letter written by Dr. Homi Bhabha himself.

Kalyan telescope construction (1965)Tata Institute of Fundamental Research

Swarup immediately began work on the design and construction of a solar array to be located at Kalyan, near Mumbai.

For this he used a set of 32 small dishes, sent by the Pott’s Hill Observatory in Australia.

Within months the new Kalyan Solar array was ready and began to make observations.

Emersion of radio galaxy PKS 0531+19 (1975)Tata Institute of Fundamental Research

But Swarup was already making bigger plans. The radio telescopes of that time had very limited resolution (more than a thousand times worse than the optical telescopes of the time) and therefore getting an accurate position of a radio source on the sky was extremely difficult.

This limitation could be overcome by the Lunar occultation technique where one could accurately determine the position of a radio source, depending on exactly when it disappeared behind the moon.

With this technique, one could identify the counterpart of every radio source in optical photographs.

Swarup realised that a sensitive radio telescope could make measurements of the position and angular size for thousands of radio sources and decide between competing theories of the origin of the Universe

Homi J. Bhabha (1965)Tata Institute of Fundamental Research

In August 1963, Bhabha extensively grilled Swarup about his plans and found that Swarup had already worked out all the details.

When Swarup asked him if he should prepare a project report Bhabha told him “Young man, do not waste your time writing a project report. Your main problem would be to collect a team; when you have managed that you can write a project report and proceed with its design and construction”.

With these encouraging words, work began on a war footing to design and build what would become the largest radio telescope in the world.

Site survey for the Ooty Radio Telescope (1964)Tata Institute of Fundamental Research

The first challenge was to find a suitable site for the new telescope. In early 1965, after an extensive site survey by Swarup and his student Ramesh Sinha, a site was found on a hill near Ooty in present day Tamil Nadu.

The site was located at an altitude of about 2100 m in the Nilgiri Hills. In late 1965, Homi Bhabha approved the construction of the ORT. A few days later, Bhabha tragically died in an air crash in Switzerland.

MGK Menon, Director TIFR laying the foundation of the Ooty Radio Telescope (1966)Tata Institute of Fundamental Research

The construction started in 1966 and was initiated by the new TIFR Director Prof. MGK Menon

Road Parallel to the Ooty Radio Telescope (1967)Tata Institute of Fundamental Research

The construction of the telescope proceeded rapidly. A parallel service road was constructed besides the telescope.

Ooty Radio Telescope construction (1967-05-24)Tata Institute of Fundamental Research

A laboratory building was constructed right next to the telescope.

Herring Bone Drain Ooty Radio Telescope (1967)Tata Institute of Fundamental Research

Adequate arrangement for water drainage were ensured.
By early 1970, the new telescope was ready.

Advertisement of the Bridge and Roof Comapny India (1970)Tata Institute of Fundamental Research

The challenges in construction were numerous and formidable. A complex engineering feat on this scale had never been attempted in India and Swarup’s group had to work closely with Indian industry to implement their design.

The Ooty Radio Telescope (1970)Tata Institute of Fundamental Research

The Ooty telescope consists of a 530 m long and 30 m wide parabolic cylinder located on a north-south hill slope whose slope equals the latitude of the location.

Ooty Radio Telescope by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research

The reflecting surface of the telescope is made of 1100 thin (0.38 mm diameter) stainless-steel wires running parallel to each other for the entire length of the cylinder.

These are supported on 24 steerable parabolic frames and total weight of the moving structure is 262 metric tonnes

Ooty Radio Telescope rotation (2018)Tata Institute of Fundamental Research

With this arrangement, it is possible to track a radio source in the sky by simply rotating the antenna along its long axis to compensate for the earth’s rotation. For this monumental effort, Govind Swarup was awarded the Padmashri (India’s fourth highest civilian Award) in 1973.

Group photo at Ooty (1975)Tata Institute of Fundamental Research

By 1971, Swarup had built up a team of nearly twenty astronomers and a similar number of engineers who shared his passion for building world class instruments and to use them to do cutting edge research.

He set up the Radio Astronomy Centre right next to the giant telescope that he had built. Through the 1970s the group worked in Ooty and made many new discoveries with the Ooty Radio Telescope.

Ooty Radio Telescope - group photograph by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research

He set up the Radio Astronomy Centre right next to the giant telescope that he had built.

Through the 1970s the group worked in Ooty and made many new discoveries with the Ooty Radio Telescope.

1975 paper by Govind Swarup published in MNRAS (1975)Tata Institute of Fundamental Research

By 1975, Swarup's team had demonstrated that the lunar occultation technique works.

1975 paper by Vijay Kapahi published in MNRAS (1975)Tata Institute of Fundamental Research

With their measurements, they were able to show that the Big Bang model for the formation of the Universe was more likely to be correct than the Steady State Model.

Group photo at Ooty of the the 15th National Space Science Symposium (2008)Tata Institute of Fundamental Research

The ORT put India on the radio astronomy map of the world and became one of the global radio astronomy centres.

Giant Meterwave Radio Telescope by Tata Institute of Fundamental Research (TIFR)Tata Institute of Fundamental Research

By the 1980s they were ready for an even bigger challenge - to build The Giant Meterwave Radio Telescope.

A view of the Ooty Radio Telescope (2018)Tata Institute of Fundamental Research

Even after almost 50 years of continuous operation, the ORT remains the world’s longest steerable telescope. It is now nearing the completion of a massive upgrade that will allow it see a much larger swath of sky at one time with significantly improved sensitivity.

Credits: Story

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

Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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