Liquid Mirror Telescope

Context : In early 2022, India’s first liquid-mirror telescope, which will observe asteroids, supernovae, space debris and all other celestial objects from an altitude of 2,450 metres in the Himalayas, saw its first light as it peered into the zenith from the Devasthal observatory in Uttarakhand. Having entered the commissioning phase, it became the world’s first liquid-mirror telescope to be commissioned for astronomy. 

What is a liquid-mirror telescope?

• The International Liquid-Mirror Telescope (ILMT) has been set up at the Devasthal Observatory campus owned by Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital in Uttarakhand.
• Located at 2,450 metres above mean sea level, there are two firsts with this — it’s the only one to have been developed for astronomy research and is also the only one of its kind to be operational anywhere in the world.
• The handful of liquid-telescopes that were previously built either tracked satellites or were deployed for military purposes. ILMT will be the third telescope facility to come up at Devasthal — one of the world’s pristine sites for obtaining astronomical observations. With ILMT set to commence full-scale scientific operations in October this year, it will work along with the 3.6-metre Devasthal Optical Telescope (DOT), the largest telescopes operating in India (of the 4-metre class). Also operating at the location is the 1.3-metre Devasthal Fast Optical Telescope (DFOT) inaugurated in 2010.

Difference between Liquid and Conventional Telescope

• A conventional telescope is steered to point towards the celestial source of interest in the sky for observations.
• The liquid-mirror telescopes, on the other hand, are stationary telescopes that image a strip of the sky which is at the zenith at a given point of time in the night.
• A liquid-mirror telescope will survey and capture any and all possible celestial objects — from stars, galaxies, supernovae explosions, asteroids to space debris.
• Conventional telescopes have highly polished glass mirrors — either single or a combination of curved ones — that are steered in a controlled fashion to focus onto the targetted celestial object on specific nights. The light is then reflected to create images.
• As opposed to this, as is evident by the name, the liquid-telescope is made up of mirrors with a reflective liquid, in this case, mercury — a metal which has a high light-reflecting capacity. About 50 litres (equal to 700kgs) of mercury filled into a container will be rotated at a fixed constant speed along the vertical axis of the ILMT. During this process, the mercury will spread as a thin layer in the container forming a paraboloid-shaped reflecting surface which will now act as the mirror. Such a surface is ideal to collect and focus light. The mirror has a diameter of 4 metre.
• Operational time : While conventional telescopes observe specific stellar sources for fixed hours as per the study requirement and time allotted by the respective telescope time allotment committee, ILMT will capture the sky’s images on all nights — between two successive twilights — for the next five years starting October 2022.
• For protecting it from moisture during monsoon, the ILMT will remain shut for operations between June and August.

Which countries are involved in its development?

• India, Belgium, Canada, Poland and Uzbekistan are the main countries who have collaborated to set up the ILMT.
• The telescope was designed and built at the Advanced Mechanical and Optical Systems Corporation and the Centre Spatial de Liège in Belgium.
• The funding, estimated to range between Rs 30 to Rs 40 crore, was jointly provided by Canada and Belgium.
• The operations and up-keep of this telescope is to be done by India.
• Along with ARIES, the other international institutes involved in the development process include the Institute of Astrophysics and Geophysics, Liège University, Belgium; the Canadian Astronomical Institutes from Vancouver, University of British Columbia; University of Montreal, University of Toronto, University of Victoria, York University, Laval University, Poznan Observatory, Poland; Ulugh Beg Astronomical Institute of Uzbek Academy of Sciences and the National University of Uzbekistan.

What is the data that will be generated and how will it be used?

• It is estimated that the ILMT is capable of generating 10-15 GB/night. With ILMT set for operations every night during nine months a year for the next five years starting October 2022, there will be data generated in gigantic volumes.
• According to international norms, the data generated by a new telescope facility will be cleaned, maintained and archived at either of the host/participating institutes, in this case, the AIRES. The norms also mandate that for an initial stipulated period, the data will be open only for researchers from these participating institutes. At a later stage, the data will be accessible to all global scientific communities.
• In order to sieve, process and analyse the large datasets, the ILMT will deploy the latest computational tools, like Artificial Intelligence, Machine Learning and big data analytics.
• Another advantage for having such large data sets is that the select data can be culled out as base data which can then be followed-up for further focused studies using spectrographs, near-Infrared spectrograph mounted on the in-house DOT.