Merak Village, Ladakh:

The Sun is the harbinger of life on Earth, but we understand so little of our nearest star. The Sun occasionally gets very angry; it then unleashes massive solar storms that take down or burn satellites and electronic equipment on Earth. To track the Sun, India seeks to set up the National Large Solar Telescope (NLST) in Ladakh.

Spearheading the project is professor Annapurni Subramaniam, Director of Indian Institute of Astrophysics (IIA), Bengaluru, who says site characterisation has been undertaken and land has been acquired. Only the final clearance is needed for this massive and much-needed project to get off the ground. It is almost a decade late.

According to the IIA, the National Large Solar Telescope will be a two-metre class optical and near infra-red (IR) observational facility. It is designed to address an array of key scientific issues related to the origin and dynamics of solar magnetic fields at a spatial resolution of 0.1-0.3 arc-second.

The instrument has a broad scope to support and substantiate the multitude of solar atmospheric observations from the space-based Aditya L1 satellite mission and ground-based solar telescope in Rajasthan’s Udaipur.

According to IIA, solar storms or Coronal Mass Ejections are large expulsions of billions of tons of plasma and its associated magnetic fields from the Sun into the interplanetary space, some of which can hit the Earth and produce geomagnetic storms. Extreme geomagnetic storms have the potential to harm space-technology dependent human life on Earth, such as disrupting radio communication, GPS signals, etc. Predicting these storms is an important area of scientific research at IIA and many other institutions in India as well.

(Above) Dr Ajay K Sood, Principal Scientific Advisor to Government of India (second from right) visiting the Merak site for the National Large Solar Telescope.

The telescope is to be installed on the banks of the Pangong Tso Lake in Merak, Ladakh, at an altitude of around 4,200 metres. Being a high-altitude cold desert, this location is best suited for optical and near IR observations. The site provides significant periods of clear skies with high transparency. The laminar winds with mild gusts throughout the day provide periods of outstanding clarity.

The National Large Solar Telescope was to be the ground-based counterpart to ISRO’s space-based solar observatory, the Aditya L-1 satellite.

Dr Subramaniam says it so happens the satellite is already in orbit and providing results while the NLST got delayed. She adds if all goes well, very soon the approvals will come through and the telescope may come up in a few years. The telescope project will cost upwards of Rs 150 crore.

Locating the telescope on the banks of the massive Pangong Tso Lake has many advantages – the water body offers a calmer atmosphere to make sharper observations and the continuous breeze will also help keep the instruments cool since solar telescopes tend to heat up very fast.

The Office of the Principal Scientific Advisor recently brought out a document ‘Mega Science Vision – 2035’ where it says “the NLST will be the largest solar telescope in the country. We recommend this as the highest priority project in solar astronomy.”

On July 6, 2024, India’s Principal Scientific Advisor Ajay K Sood visited the site of the solar telescope and took stock of the developments. “The region is known for its exceptionally clear skies and low light pollution, making it an excellent location for stargazing.”