Indian Astronomical Observatory (IAO)

About the Indian Astronomical Observatory (IAO)

• Location:
  • Indian Astronomical Observatory is located in Hanle village near Leh in Ladakh.
  • Indian Astronomical Observatoryis situated at an altitude of 4500 meters atop Mt. Saraswati in the vast Nilamkhul Plain in the Hanle Valley of Changthang.
  • The site is a dry, cold desert with sparse human population and the ancient Hanle monastery is its nearest neighbour.
• Key highlights of Indian Astronomical Observatory, Hanle:
  • Hanle is one of the world’s highest located sites for optical, infrared and gamma-ray telescopes.
  • It is currently the ninth highest optical telescope in the world.
  • It was established in 2001 and is operated by the Indian Institute of Astrophysics, Bangalore.
• Major Telescopes at Indian Astronomical Observatory, Hanle site:
  • Himalayan Chandra Telescope (HCT): It is an optical-infrared telescope named after India-born Nobel laureate Subramanian Chandrasekhar. This telescope is remotely operated from CREST, Bangalore using dedicated satellite links.
  • GROWTH-India Telescope: It is the country’s first fully robotic research telescope.
  • High Altitude Gamma Ray Telescope (HAGAR): It is an atmospheric Cerenkov experiment with 7 telescopes setup in 2008.

Indian Astronomical Observatory: Major Highlights of the Study

• Objective: To find ideal locations around the world to build next big telescope based on local meteorological data collected over many years.
• Plan of action: As part of the study, researchers have carried out a detailed analysis of the night time cloud cover fraction over 8 high altitude observatories:
  • Indian Astronomical Observatory (IAO) in Hanle, Merak (Ladakh) and Devasthal (Nainital) in India,
  • Ali Observatory in the Tibet Autonomous Region in China
  • South African Large Telescope in South Africa
  • University of Tokyo Atacama Observatory
  • Paranal in Chile
  • National Astronomical Observatory in Mexico.
• Findings of the study:
  • The Paranal, located in a high-altitude Atacama Desert in Chile, is the best site in terms of clear skies with around 87% of clear nights in a year.
  • The Hanle site, which is much drier than Devasthal and has around 270 clear nights in a year, is one of the emerging sites for infrared and sub-mm optical astronomy (This is because water vapour absorbs electromagnetic signals and reduces their strength).
  • IAO-Hanle, and Ali observatories, which are located around 80 km from each other, are similar to each other in terms of clear night skies.
  • Devasthal has a slightly larger number of clear nights compared to the other sites in the sub-continent but are affected by monsoons for about three months in a year.
  • However, night observations at Indian Astronomical Observatory-Hanle from 2m-Himalayan Chandra Telescope (HCT) are possible throughout the year without any interruption due to monsoons.

Indian Astronomical Observatory: Dark Sky Reserve

• Recently, in September 2022, the Department of Science & Technology (DST) has announced the setting up of India’s first Dark Sky Reserve in Hanle, Ladakh.
• A Dark Sky Reserve is a designation given to a place that has policies in place to ensure that a tract of land or region has minimal artificial light interference.
• The International Dark Sky Association is a U.S.-based non-profit organization that designates places as International Dark Sky Places, Parks, Sanctuaries and Reserves, depending on the criteria they meet.

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