ON January 20, 1962, Govind Swarup, a 33-year-old aspiring radio astronomer working at Stanford University, received a telegram from Homi Bhabha, Director of Tata Institute of Fundamental Research (TIFR) in Mumbai (then Bombay), who was laying the foundations for the growth of modern science in India. It read: “We have decided to form a radio astronomy group stop letter follows with offer stop.” In the letter that followed, which Swarup received on April 3, 1962, Bhabha wrote: “If your group fulfils the expectations we have of it, this could lead to some very much bigger equipment and work in radio astronomy in India than we can foresee at present.”
Swarup, imbued with a spirit of nationalism (having been inspired in childhood by Mahatma Gandhi and the novels of Premchand, and later by people like Jawaharlal Nehru, C.V. Raman and M.N. Saha during his days at Allahabad University), saw this as a golden opportunity to realise his dream of working at the frontiers of observational astronomy in India and decided to accept the offer. He joined TIFR in April 1963. Even before he left the United States, Swarup began to think about the kind of work he would do and the kind of equipment that working at the frontiers would need. With the experience he had gained by working with the greats in the field, first at the radio physics (RP) division of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Sydney, Australia, and later in the U.S., first at the Fort Davis Radio Astronomy Station in Texas of the Harvard Observatory and then at Stanford University while doing his PhD, Swarup set out to do what Bhabha expected of him.
In fact, he more than fulfilled Bhabha’s expectations and turned his words into prophecy by not only building world-class radio astronomy facilities but also putting India firmly on the radio astronomy map of the world by training, mentoring and nurturing a large group of students, engineers and microwave electronics specialists who would keep his legacy for years to come. But the void he left when he passed away on September 7 will be hard to fill. While people of his heritage will certainly carry forward the knowledge, skill and insight he had imparted, it will be hard to find someone with similar originality and inventiveness, a similar vision of science, the same missionary zeal, a never-say-die spirit and a single-minded focus to achieve a goal.
Swarup was born in Thakurdwara, a town in western Uttar Pradesh, about 50 kilometres from Moradabad, in 1929. He studied at Allahabad University obtaining a degree in physics in 1948 and a postgraduate degree in 1950. He was influenced by his teacher K.S. Krishnan, who had worked with C.V. Raman and made contributions to his Nobel Prize winning work in 1928. Krishnan had taught electricity and magnetism in 1946-47. As destiny would have it, after completing his postgraduation, Swarup joined the National Physical Laboratory (NPL) in Delhi, which was founded in 1947 with Krishnan as its founding Director.
On the road to radio astronomy
With Krishnan’s interests having shifted to quantum theory of magnetism, Swarup began to work on paramagnetic resonance under his guidance. Krishnan put Swarup on the job of building suitable equipment to study the phenomenon of electron spin resonance at a wavelength of 3 centimetres (or 10 GHz frequency). Although he had no previous experience in building an electronics instrument, Swarup succeeded in making the required apparatus in 18 months by cannibalising parts from the several radar sets that NPL had acquired from discarded Second World War equipment. The famous ‘Rad Lab’ volumes (a 28-volume classified compilation of results of microwave radiation research done at MIT’s Radiation Laboratory during the Second World War, a set of which had ended up at NPL), had come to Swarup’s rescue. This is where Swarup first learnt to dirty his hands to develop something new. It was Krishnan who set Swarup on the road to radio astronomy, the area in which he made an indelible mark.
With the discovery of radio wave emission from our galaxy in 1930, radio astronomy, aided by research in microwave research and radar development during the War, began making rapid strides. Some remarkable discoveries were made in the following years, particularly by the RP Group at Sydney led by Joseph Pawsey and the Martin Ryle group at Cambridge. Krishnan attended the 1952 general assembly of the International Radio Science Union (URSI), the only forum that discussed radio astronomy those days, and listened to many stalwarts of radio astronomy.
On his return, Krishnan gave a colloquium at NPL describing the latest developments in radio astronomy. “These caught my imagination… and I… was fascinated by this new field,” Swarup wrote in 2006 in Journal of Astronomy Heritage and History (JAHH). Krishnan initiated radio astronomy research at NPL and recommended Swarup’s name for a two-year fellowship under the Colombo Plan to work at the RP division in Sydney to get exposed to radio astronomy research at the frontiers. With that began Swarup’s grand journey as a radio astronomer.
At Sydney, Swarup and R. Parthasarathy (who was at Sydney to develop a 10.7 m solar radio telescope for the Kodaikanal Observatory in Tamil Nadu) got the opportunity to work with the L-shaped grating radio interferometer telescope at Potts Hill, which had 1.7 m parabolic dishes. The two converted its operating wavelength from 21 cm to 60 cm (500 MHz frequency) and studied the limb brightening of the quiet sun at that frequency as had been predicted before. Swarup and Parthasarathy showed that the prediction was indeed correct.
Radio astronomy research
“For us,” wrote Swarup in JAHH, “this was a great experience: building dipoles, a transmission line network and a receiver system; making the observations; and finally, carrying out data reductions….” In 1955, the RP group decided to scrap 32 parabolic dishes of the east-west (E-W) arm of the interferometer. With Krishnan’s idea of starting radio astronomy research in India in his mind, Swarup requested Pawsey to donate the discarded dishes to NPL. Pawsey readily agreed with the proviso that India should pay for their transportation. Krishnan welcomed this proposal. Swarup had indicated to Krishnan that he planned to use the 32 dishes to set up a grating interferometer with a baseline of 640 metres for simultaneous dual frequency solar observations at 500 MHz and 165 MHz. Krishnan wrote back to Swarup: “I agree with you that we should be able to do some radio astronomy work even with the meager resources available.”
Swarup returned to NPL in August 1956 and immediately got down to designing and building a receiver system for operating the instrument at 500 MHz. However, Krishnan could not succeed in getting an approval from the Council for Scientific and Industrial Research (CSIR) for transporting the dishes from Sydney. Although Krishnan had managed to create a radio astronomy group, real experimental work could not take off because the foreign exchange situation at that time proved to be a hurdle even for erecting a modest telescope with gifted dishes. With no immediate resolution in sight, Swarup decided to go to the U.S. for a year or two. In the next couple of years, most of the other members of the group (who would later become noted radio astronomers in their own right) also left NPL. But before Krishnan’s death in June 1961, the dishes arrived from Sydney after the CSIRO decided to bear the transportation cost too.
Bhabha’s telegram to Swarup was actually in response to a joint letter written in September 1961 by four Indian radio astronomers wanting to return to India. At the urging of Swarup, Indian radio astronomers T. Krishnan from the RP group, T.K. Menon from Harvard, M.R. Kundu from France and Swarup met on the sidelines of the International Astronomical Union (IAU) meeting in August 1961 and planned to send a proposal to the heads of major scientific agencies and key research institutions in India, which included Bhabha. Only Bhabha’s response was encouraging. Like Swarup, the others, too, had similarly heard from Bhabha. But only Swarup accepted Bhabha’s offer and returned to India in March 1963. For the others, the offer was unsatisfactory.
Thus, it was Swarup who all by himself created that nascent radio astronomy group at TIFR and nurtured it to achieve major milestones in a very short period. Barring T. Krishnan, the other two radio astronomers joined TIFR in later years, Kundu in 1965 and Menon in 1970. Though they, particularly Kundu, contributed significantly to the early growth of radio astronomy at TIFR, both eventually went back to the U.S., Kundu in 1968 and Menon in 1974. The commitment, will and determination to achieve is what sets Swarup apart from the others. It should be noted that, unlike the general trend, particularly today, Swarup decided to work towards a formal PhD only in 1957, when he moved to Stanford (to work under R.N. Bracewell) from Fort Davis Radio Astronomy Station of Harvard Observatory, where he had initially gone from NPL. Swarup had already produced significant observational work in Australia under Pawsey. At Fort Davis, he had made an even more significant discovery in December 1956: the so-called U-shaped radio burst in the frequency from the sun. This is another indicator of his attitude towards scientific research.
Lunar occultation
On Bhabha’s request to NPL/CSIR, the 32 dishes obtained from the CSIRO were transferred from NPL to TIFR in mid 1963. In June 1963, Swarup came across two interesting papers in Nature , one on using the technique of lunar occultation to observe the first quasar to be discovered (called 3C273) and the other on characterising these compact but powerful radio sources. Quasars are star-like radio sources that are actually supermassive black holes emitting highly energetic radiation due to the accretion of energetic gases as they fall into the black holes they surround. But these objects were produced early in the universe and are, therefore, at great distances from us. Also, it meant that such objects are faint, thus making accurate measurements of their sizes difficult. So, in order to improve the observational accuracy significantly, you need telescopes with a large collecting area to receive these emitted electromagnetic waves.
Swarup’s mind began to work overtime on this. He reasoned that lunar occultation with a bigger telescope could be used for accurate angular size measurement of thousands of such distant radio sources, which can be then used to discriminate between competing cosmological models—steady state or Big Bang—and arrive at the correct description of the evolution of the universe. He estimated that a collecting area of about 10,000 square metres would be required for accurate measurements, which would be four times the collecting area of the then largest antenna with a diameter of 76 m at Jodrell Bank. Moreover, it had to be steerable to be able to track a particular source for long hours. That did not seem feasible, certainly not in India. He had to come up with a clever solution; he came up with one very soon.
Parabolic cylindrical telescope
Apparently, one day, sitting in the TIFR library that overlooks the Arabian Sea and provides a beautiful view of it, Swarup got this brilliant idea. He conceived of a large parabolic cylindrical telescope that could be rotated on its axis. If built on an N-S hill at a location close to the equator, with its slope angle equal to the latitude of the place, it would make the telescope axis parallel to the earth’s axis of rotation. This meant that a source could be tracked and observed for a long time by simply rotating the cylindrical antenna at the same rate as the earth’s rotation. Simple, elegant and ingenious!
He first sounded out M.G.K. Menon, the second in command at TIFR, who responded enthusiastically and took him to meet Bhabha. He was excited with the proposal and grilled Swarup for over two hours on the details. When Swarup asked him if he should write a detailed project document, Bhabha apparently 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 submit a project report….” By early 1965, Swarup managed to build a team of seven, which included Kundu. By the end of 1963, Swarup, along with his first two students, who were products of the Atomic Energy Establishment’s Training School, had already started setting up the 32 Potts Hill dishes to build a radio interferometer at Kalyan near Bombay to observe the sun, and completed the work in early 1965, in about 15 months. There was an urgency to achieve this because the next solar cycle (which comes roughly once in 11 years) was to begin, giving an excellent opportunity for interesting results. The Kalyan telescope was used to investigate the radio emission properties of the quiet and active sun in 1965-68. The telescope was, in some sense, a training ground before the team took on the big challenge of building the large cylindrical telescope.
In early 1965, a suitable site was located at Muthorai near Ooty (Udhagamandalam). Bhabha personally visited the site and initiated the formalities of acquiring the land. These were done quickly with the support of the former President R. Venkataraman, who was then the Finance Minister of Tamil Nadu, and by the end of 1965 Bhabha gave his approval to start the project.
Ooty Radio Telescope
The telescope was completed in December 1969. The first occultation observations were made on February 18, 1970. With the Ooty Radio Telescope (ORT), lunar occultation observations of more than 1,000 radio sources were made in the 1970s. This resulted in accurate positions and angular sizes to arc-second resolution of these sources. The data provided independent support to the Big Bang model. By early 1971, the radio astronomy group at TIFR had grown to 16 members. The ORT is a parabolic cylinder 530 m long in the N-S direction and 30 m wide in the E-W direction, built on a hillside, roughly with 11° angle slope, equal to the latitude of the place. The intended operating RF band for ORT being around 326.5 MHz (92 cm wavelength), to reflect such large wavelength radiation, a solid surface is not necessary. The reflecting surface is made of 1,100 steel wires 530 m long and 0.38 mm diameter, which is supported by 24 solid parabolic steel frames separated by 23 m. Since the telescope is a cylinder, the focus for the reflected radiation is actually a 530 m long line placed along which are 1,024 dipoles to detect the reflected waves.
The effective ‘collecting area’ of the ORT is about 8,000 sq. m. To have a similar collecting area, a dish antenna should be of 140 m diameter, which would have been impossible to build in the 1960s. Bhabha died in January 1966 in a plane crash in the Swiss Alps and did not live to see this grand edifice, which is even now yielding good science, and the growth of the discipline at TIFR.
The ORT was built indigenously. It was a real technical challenge to build such a complex engineering structure in the 1960s, when Indian industry had not matured enough, but guided by Swarup and his team, whose median age was only 27. Tata Consulting Engineers (then called Tata Ebasco) did the structural and engineering design, and the Calcutta firm Bridge and Roof carried out the mechanical construction. When the consultant engineers wanted their design reviewed by overseas experts, Swarup apparently retorted: “In that case I could have as well continued doing radio astronomy abroad.”
The successful indigenous design and construction of the ORT led to the development of a large microwave antenna industry in India, starting with the construction of the Arvi satellite earth station near Pune in 1971 by Electronics Corporation of India Ltd (ECIL) with which Swarup was involved closely. The entire technology for designing and constructing a microwave antenna had been transferred to ECIL. But when it was decided to build the second antenna at Arvi as a turnkey project by Nippon in the 1990s, Swarup, according to the then Current Science Editor S. Ramaseshan, apparently said his blood boiled. In the journal, he quoted Swarup as saying: “It is a shame on the Indian electronics companies who already possess the antenna technology.”
“Building the ORT,” says S. Ananthakrishnan, a long associate of Swarup and a core member of his team, “trained a core group of young scientists and engineers on how to build large antennas, sophisticated electronics, analyse large radio data, publish in reputed international and national journals, and prepared them for even larger projects.” After some 10 years of successfully operating the ORT, Swarup began to think of a bigger project although he could have easily rested on the laurels of the ORT’s success. But Swarup was made of different stuff.
The GMRT Project
Ananthakrishnan recalls how the idea of the next large project, the Giant Metrewave Radio Telescope (GMRT) took shape: “In 1980-83, there were intense discussions in the group on how to build the world’s most sensitive radio telescope at low frequencies of 100 to 1,500 MHz in a cost-effective manner using indigenous technology. Swarup was one of the original ‘Make in India’ persons.” A highly sensitive radio telescope at metre wavelength was necessary to answer some outstanding questions about the formation of galaxies in a Big Bang universe. If, as conjectured, galaxies formed out of condensation of hydrogen clouds in the early epoch, the signature of primordial hydrogen in the form of the characteristic 21 cm emission line from hydrogen should be detectable. Because of the expansion of the universe, a 21 cm radiation would have stretched to metre wavelengths. Also, these early epoch signals would be very weak. Hence the need for building metrwave radio telescopes with very large collecting area (for high sensitivity).
Swarup’s original idea was to build a very large array consisting of several parabolic cylinders placed in a Y shape over several kilometers, much like the Very Large Array (VLA) built in the early 1980s in New Mexico. The sizes of the cylinders were to be about three-four times that of the VLA dishes, but would operate at low frequencies as a complementary facility to the high frequency VLA. The plan, according to Ananthakrishnan, went through several iterations and discussions, both among Indian and foreign experts, and it was ultimately decided that the GMRT would consist of parabolic dishes, and not dashes (cylinders).
“The conversion of ‘dashes’ into ‘dishes’ involved considerable design changes, and higher costs. It also required innovative ideas, which required both scientists and engineers to spend several days and nights. The final idea was a low-cost innovative design, which became the signature GMRT dishes,” he says.
Conventional parabolic dishes with high sensitivity at such wavelengths become expensive because of structures needed to withstand the high wind loads on the solid reflecting surfaces. Swarup came up with an ingenious design, which he called the “Indian rope trick”. This brought down the GMRT cost greatly without compromising on its sensitivity and accuracy. Christened SMART by Swarup, an acronym for Stretched Mesh Attached to Rope Trusses, in this the conventional back-up solid structure of the antenna is replaced by a series of rope trusses made of stainless steel wire ropes supported by radial parabolic frames. A low solidity wire mesh, stretched at appropriate tension over the rope trusses, forms the reflecting surface.
Mammoth radio telescope
The GMRT consists of 30 steerable parabolic dishes of 45 m diameter each located in a large Y-shaped array, which extends 14-15 km in length along each arm (North-East, North-West and South). Twelve of them form a compact array at the centre of the Y (see graphic). The design is equivalent to a 25 km-sized antenna, which makes GMRT a mammoth radio telescope array and the most sensitive one in the world at low frequencies even today. “Several engineering innovations were implemented along the way. The engineering contractors faced formidable problems, but the array telescope was completed in 2000. Although Govind had retired by then, it could not have been achieved without his inspiring leadership as well as a very energetic scientific and engineering team,” says Ananthakrishnan.
According to Ramaseshan, Swarup tried hard to get Indian engineers back from the U.S. for building the GMRT but failed. He apparently said in disgust: “They are only interested in money; all this talk of lack of challenge in India is bunkum, you cannot ask for a greater challenge than GMRT.” Interestingly, as he once told this writer, despite his many lectures at the various Indian Institutes of Technology about the GMRT, students did not show much interest in it. But, with his ‘one-track mind’ and aided by the ORT team, he set about training his students and those who joined him and achieved what would have seemed impossible in the Indian context. After visiting GMRT, Subramanyan Chandrasekhar, the Nobel Laureate astrophysicist, wrote: “Shouldn’t have thought that such things could be done.”
The GMRT is being used extensively by scientists from more than 50 countries and is today among the front-ranking telescopes of the world. It is likely to retain this position for several years to come. With its recent upgrades spanning 2012- 2019, it has become the most sensitive radio array for investigating outstanding problems of astrophysics and cosmology at metre wavelengths (< 1,500 MHz). Only recently, the GMRT detected radio emission from a galaxy that is 12 billion light years away, the most distant radio galaxy ever observed.
Swarup was equally passionately concerned about the status of higher education in India. “I dream of India where we have world-class universities,” Swarup had said in an interview. He felt education and research should be integrated. He was the prime mover behind the concept of setting up the Indian Institutes of Science Education and Research (IISERs) offering a five-year integrated course. Between 1996 and 2004, he determinedly tried to get support for the proposal he and V.G. Bhide, the former Vice Chancellor of Pune University, had drawn up. The proposal was approved in 2004 after the Science Advisory Council to the Prime Minister (SAC-PM), headed by C.N.R. Rao, lent support to the initiative of setting up five IISERs. Today, there are more IISERs, suggesting the success of the model. “I consider this a bigger achievement than building the GMRT,” Swarup had told the interviewer.
Ananthakrishnan said: “His ready and infectious smile hid a sharp mind. An innovator with high skills, he was extremely hard working and focussed on his goal. He had this ability to break down complex engineering problems into parts and analyse those based on simple principles of physics and engineering and later assemble all those parts to make a whole. Most of all, he enjoyed the company of young bright minds and could argue with them on equal terms on scientific problems; it invigorated everyone. This ambience was different from what one finds in many academic circles today in India.”
His vision has inspired generations of students and engineers since 1963. The astronomy community will miss him greatly.
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