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doi:10.1038/nindia.2013.104 Published online 8 August 2013

India chips in to make largest telescope ever

Jaimon Joseph

India is building key parts of the largest optical and infrared telescope ever made by man — the Thirty Meter Telescope (TMT). Last month (July 26, 2013), the country pledged to bear about 10 per cent of the total cost of the $1.5-billion TMT, to be completed by 2022 at Mauna Kea, Hawaii, one of the clearest spots for astronomical observation in the world.

Five countries — the US, Canada, China, Japan and India — are collaborating on the prestigious project with India's share at roughly $160 million or Rs. 1,000 crore. In comparison, India's investment in CERN, Geneva for the Big Bang experiment was a mere $25 million.

What the TMT will finally look like.
© TMT Observatory Corporation

"Nothing like this exists in the world right now. India is building the edge sensors, the actuators, the segment support systems and some of the mirror assemblies on the project," B Eswar Reddy, TMT's India programme director told Nature India.

Almost Rs 600 crore worth of equipment will be designed and manufactured in India. The Indian Institute of Astrophysics (IIA), Bangalore, the Inter-University Centre for Astronomy and Astrophysics (IUCCA), Pune and the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital have come together to design the components.

The institutes have passed on design specifications to companies like General Optical Asia Ltd. (GOAL), Puducherry; Avasarala Technologies, Bangalore and Godrej, Mumbai for production of these components. Reddy says the first batch of edge sensors and actuators have already been tested at the Jet Propulsion Lab (JPL), USA and the feedback is "extremely positive".

The largest existing optical telescopes in the world are only about 10 metres across. They were built more than two decades ago.

Imagine a concave mirror, roughly circular in shape. It measures thirty meters across — about one third the length of a football field. It's hard to make a slab of glass that big. So 492 smaller, six pointed pieces are used to make it. Each of those pieces is about 1.44 m across, about the height of a seventh standard school kid.

The pieces have digital sensors that constantly correct deformations caused by temperature, gravity, wind and seismic vibrations. The sensors correct shifts in atmospheric density that blur light from distant stars – the first telescope in the world to do so. They also ensure that all 496 pieces are perfectly aligned and move together as one flawless mirror.

The sensors do this through actuators — computer controlled pistons and levers attached to the bottom of each mirror — which gently knead and distort its curvature according to the need of the hour. Each mirror will be mounted on a Segment Support Assembly (SSA), with a number of tiny but remarkably accurate sub-components.

Besides the TMT in Hawaii, two other super-sized telescopes are simultaneously being built in Chile — the European Extremely Large Telescope (E-ELT), 39.3 m in diameter funded by Europe, and the Giant Magellan Telescope, 24.5 m in diameter funded by the US, Australia & Korea. For a long time, Indian astronomers weren't sure which of these projects they should invest in.

"The E-ELT price tag was beyond India and GMT wanted only monetary payments. TMT was okay with contributions mostly in kind, which means that almost 70 per cent of the money can be spent in India to benefit Indian industry and academia," says Somak Raychaudhury from Presidency Univerisity, Kolkata's department of astrophysics. He and another scientist Ashoke Sen from Assam University Silchar, are currently observers on the TMT project.

India has never made segmented mirrors before, says Ajit Kembhavi from the Inter University Centre for Astronomy and Astrophysics, Pune. "We're now setting up a manufacturing unit within the country. Once we master the technology, we're bound to get contracts from abroad for other projects too," he says. Similarly, the software to move the telescope, process astronomical data and create visualizations, will be made by Persistent Systems, Pune.

The Department of Science and Technology (DST) and the Department of Atomic Energy (DAE) will jointly fund the Indian component. According to the arrangement, Indian astronomers will get observational time in proportion to India's share in the total project cost.

The TMT will resolve objects three times better than the 10 m-class telescopes at Hawaii and 12 times better than the Hubble Space Telescope (HST).

It is expected to receive light from some of the oldest and farthest stars in our universe and thus reveal secrets about its birth and evolution of galaxies. It will observe dark matter, believed to make up almost 95% of our universe. It will also observe dark energy, a strange repulsive force that is pulling the universe apart.

The TMT will locate black holes– gravitational cesspools that suck up everything around them. It could identify potential life bearing planets far beyond our galaxy – the light they reflect, carries tell tale signs about the presence of oxygen and water in their atmosphere. Within our own solar system, the TMT will clearly pick out tiny asteroids and satellites around far away planets.

Participation in the TMT experiment will allow Indian scientists to cross-check data they get from India's Giant Metre Wave Radio Telescope (GMRT); from ASTROSAT, India's dedicated astronomy satellite and from the upcoming Square Kilometer Array, the world's largest and most sensitive radio telescope.

"It is hard to predict what the spinoffs will be for lay people. Remember, digital cameras and USB drives came from the last round of mega astronomical projects like the Hubble Space Telescope. When billions of dollars are spent on new technology, spinoffs always happen", Raychaudhury adds.