ISRO Missions and Discoveries

International Liquid Mirror Telescope (ILMT)


From UPSC perspective, the following things are important :

Prelims level : International Liquid Mirror Telescope (ILMT)

Mains level : Not Much

The four-meter International Liquid Mirror Telescope (ILMT) saw the first light recently, gazing out from its vantage on Devasthal, a hill in Uttarakhand.

What is the ILMT?

  • The telescope has been built by a collaboration of scientists from Canada, Belgium and India.
  • It is located at an altitude of 2,450 metres on the Devasthal Observatory campus of the Aryabhata Research Institute of Observational Sciences (ARIES) in Nainital district.
  • A large pool of mercury placed in a vessel is spun around so fast that it curves into a parabolic shape. Since mercury is reflective, this shape helps in focusing the reflected light.
  • Nearly 50 litres of mercury, weighing close to 700 kilograms, is spun hard to form a paraboloid mirror of just 4 mm thickness and a diameter of about 4 metres.
  • A thin sheet of mylar protects the mercury from the wind.
  • Once it starts making observations, the telescope will collect gigabytes of data, which will need to be analysed using artificial intelligence and machine learning (AI and ML) tools.

It’s utility

  • The telescope will make sky surveys possible and obtain images that can help observe transient phenomena.
  • It will help analyse events such as supernovae and record the presence of space debris or meteorites — basically, watch the skies.

What is the first image?

  • The first image made by the telescope consisted of several stars and a galaxy, NGC 4274, which is 45 million light years away.
  • The telescope, having a primary mirror that is liquid, cannot be turned and pointed in any direction.
  • It “stares” at the zenith and watches the sky as the earth rotates, thereby giving a view of different objects.
  • This property can be used to scan and survey the sky, and observe transients and moving objects such as meteorites.
  • It will work in tandem with the existing 3.6-metre Devasthal Optical Telescope.


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