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Insights into Editorial: India gets world’s first liquid-mirror telescope for astronomy




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, has seen its first light.

It has now entered the commissioning phase and will start scientific observations sometime in October 2022.

The International Liquid Mirror Telescope (ILMT), which is the largest in Asia, has been set up at the Devasthal Observatory.

The observatory is housed in the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital in Uttarakhand.

The International Liquid Mirror Telescope (ILMT) is the only liquid-mirror telescope operational anywhere in the world.

It will also hold the unique tag of being the maiden liquid-telescope globally to be designed exclusively for astronomical purposes.


How will Liquid Mirror telescope work?

The observatory has been developed by scientists from India, Belgium, and Canada. The Liquid Mirror telescope is a 4-metre-diameter rotating mirror made up of a thin film of liquid mercury to collect and focus light.

Mercury is used as it is a reflective liquid and is spun so that the surface is curved into a parabolic shape which is ideal for focusing light.

To protect its distortions from the wind, it is covered by a thin transparent film of mylar.

The reflected light passes through a sophisticated multi-lens optical corrector that produces sharp images over a wide field of view.

The unique telescope will monitor the sky for transitory or variable objects such as supernovae, gravitational lenses, space debris, and asteroids.

International Liquid Mirror Telescope (ILMT) is the country’s first and largest liquid-mirror telescope, as well as the largest in Asia.


Threat of Space Debris:

  1. According to an old 2021 data, around 6,542 satellites are there in space, out of which 3,372 satellites are active and around 3,170 are inactive and adding to the already crowded space junk.
  2. It is said that space debris is no longer a nuisance as it has already reached a level of grave threat.
  3. Evidently, in November 2021, a chunk of a Chinese satellite almost hit the International Space Station (ISS), although the mishap was averted, the threat is constantly looming as a mere small nut bottle can damage more than a cannon because of the speed at which the debris roam around in space.
  4. That is the reason why, acting as a responsible nation, India has stepped up to establish this world’s first liquid mirror telescope to correctly detect, predict the path of space junk, debris and asteroids to avoid collision, mishap and loss of crucial military and civilian communication satellites.
  5. With this India yet again proves its prowess in the space sector as well as taking a lead as a space detective to protect the World from any mishap.
  6. The telescope was designed and built at the Advanced Mechanical and Optical Systems Corporation and the Centre Spatial de Liege, Belgium.
  7. The major instrumentation funding was jointly provided by Canada and Belgium while India will be responsible for the operations and upkeep of the telescope.


How is it different from a conventional telescope?

  1. A conventional telescope is steered to point towards the celestial source of interest in the sky for observations.
  2. 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.
  3. In other words, a liquid-mirror telescope will survey and capture any and all possible celestial objects — from stars, galaxies, supernovae explosions, asteroids to space debris.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. Such a surface is ideal to collect and focus light. The mirror has a diameter of 4 metre.
  9. Another difference between the two is their 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.
  10. For protecting it from moisture during monsoon, the ILMT will remain shut for operations between June and August.


Other Significance of ILMT:

Enormous amount of data (10-15 GB/night) will be generated. This will be significant for the global scientific communities.

Latest computational tools, like Artificial Intelligence, Machine Learning and big data analytics will be deployed for screening, processing and analyzing the data.

Selected data can be used as a base data for carrying out further focused research using spectrographs, near-Infrared spectrograph mounted on the in-house DOT.

Over the past one month, all collaborators have been working in fine-tuning and setting up the operations of the ILMT before it is readied for full-scale scientific observations post the monsoon season.

Unlike the conventional telescopes that can be steered to track specific stellar source objects, the ILMT will be stationary.

It will basically carry out observations and imaging at the zenith, that is, of the overhead sky. This is  a survey telescope having high potential for discovering newer objects



The ILMT data will be ideally suited to perform deep photometric and astrometric variability surveys over a period of five years.

The ILMT will operate every night for five years and carry out daily imaging except between June and August monsoon months, a precaution to protect the instruments from humid conditions.

With such large voluminous data soon to be generated, Experts confirmed that the applications and algorithms using big data, Machine Learning (ML) and Artificial Intelligence (AI) will be implemented while classifying the celestial objects.