The sun’s atmosphere is an ideal place to
study and test many magneto-hydro-dynamic (MHD) processes controlling turbulent
plasma. Sadakh, the cold desert in India, will have the world’s largest
state-of-the-art solar telescope on the earth soon for this purpose. This
National Largest Solar Telescope (NLST) will be set up at high altitude Pongong
Tso Lake Merak near Line of Actual Control on the Sino-Indian divide. It will
be unique globally because the largest solar telescope, the Mc-Math-Pierce
Solar Telescope, in the world at present is 1.6 meters. It is situated in Kitt
Peak national Observatory at Arizona in the United States. The NLST will have
the reputation of being the world’s largest telescope till 2020. It is expected
that a larger telescope may become operational in the US by 2020-2021.
NLST is a Gregorian multi-purpose open
telescope. It will be on-axis with the provision of carrying out night time
stellar observations using a spectrograph. It will be able to study particles
spread across 50 kilometers of the sun. It is expected to resolve features on the
sun of the size of about 0.1 arcsec. The focal plane instruments are to
include a high resolution polarimetric package to measure polarization with an
accuracy of 0.01 %, a high spectral resolution spectrograph to obtain spectra
in 5 widely separated absorption lines simultaneously and high spatial
resolution narrow band image in various lines.
Tech
specs
The telescope will be fitted with a 2 meter
reflector which will enable scientists to carry out cutting edge research to
understand the fundamental processes taking place on the earth. The design is
by an international company which also designed the 1.5 meter telescope located
at Tenarife Island in Spain. All the telescope’s instruments will be developed
by the Indian Institute of Astrophysics (IIA) and will be remotely operated
through the master control facility at Bangalore. The link will be through a
satellite which will be provided by the Indian Satellite Research Organisation
(ISRO). Night-time observations will be made using an instrument which will be
built in collaboration with the University of Hamburg, Germany.
Scientists will study the sun’s microscopic
structure, and long term changes in the earth’s climate and environment. This
will provide useful data to carry out research in order to minimize or remove
disruptions to communication network and satellite due to periodic solar-winds.
The telescope will address the fundamental
question about the nature of solar magnetism. It will aim to resolve flux tubes
and measure their strength; address the development of magnetic fields on the
sun which are responsible for almost all the observation phenomena on the sun.
They include solar dynamo, solar cycle and solar variability that determine and
control space weather.
Selection
of the Site
To install the telescope, the Indian Institute
of Astrophysics studied two other sites-Hanle, Leh and Devasthal near Nainital
in Uttarakhand but eventually opted for Merak in Ladakh.The cloudless skies and
low atmospheric water vapour have made it one of the best sites in the
world for optical, submilimeter and millimeter wavelengths.
The Himalayan regions provide certain
atmospheric conditions required for such telescope functioning. It provides a
large number of clear hours for making observations with very good visibility.
The water vapour in the field is also low which helps making observations in
infrared wavelength for high accuracy of magnetic field and velocity
measurements. The lake side provides better seeing condition. Because of lake
water, there is extremely low water vapor content and this is unaffected by the
monsoon.
The NLST project is a major multi-party
initiative involving IIA, ISRO, Aryabhatta Research Institute of Observational
Sciences, Tata Institute of Fundamental Research (TIFR) and Inter University
Center for Astronomy and Astrophysics (IUCAA). The project will involve an
investment of over Rs 250 crore, most of which will go in procuring equipment.
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