The Indian Astronomical Observatory (IAO) is a high-altitude astronomy station located in Hanle, India and operated by the Indian Institute of Astrophysics. Situated in the Western Himalayas at an elevation of 4,500 meters (14,764 ft), the IAO is one of the world's highest located sites for

optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

and gamma-ray telescopes. It is currently the tenth-highest optical telescope in the world.

Location

The Indian Astronomical Observatory stands on Mt. Saraswati, Digpa-ratsa Ri, Hanle in the south-eastern

Ladakh Ladakh () is a region administered by India as a union territory and constitutes an eastern portion of the larger Kashmir region that has been the subject of a Kashmir#Kashmir dispute, dispute between India and Pakistan since 1947 and India an ...

union territory of India. Accessing the observatory located near the Chinese border (

Line of Actual Control The Line of Actual Control (LAC), in the context of the Sino-Indian border dispute, is a notional demarcation lineAnanth KrishnanLine of Actual Control , India-China: the line of actual contest, 13 June 2020: "In contrast, the alignment of ...

), requires a ten-hour drive from

Leh Leh () is a city in Indian-administered Ladakh in the Kashmir#Kashmir_dispute, disputed Kashmir region. The application of the term "administered" to the various regions of Kashmir and a mention of the Kashmir dispute is supported by the WP:TE ...

city.

Nyoma Nyoma is a principal village of southern Ladakh in India, the headquarters of an eponymous subdivision, tehsil, community development block and Indian Air Force Base in the Leh district.B. V. Sreekantan recommended that a national, large optical telescope must be taken up as a priority project. The search for the observatory site began in 1992 under the leadership of Arvind Bhatnagar. The scientists from the Indian Institute of Astrophysics found the site at Hanle. The first light was seen by the Observatory 2-metre telescope on the midnight hour between 26 September and 27 September 2000. The satellite link between the Centre for Research and Education in Science and Technology (CREST), Bangalore, and Hanle was inaugurated by the then Jammu and Kashmir Chief Minister

Farooq Abdullah Farooq Abdullah (born 21 October 1937) is an Indian politician who serves as current president of the Jammu & Kashmir National Conference. He has served as the chief minister of Jammu and Kashmir on several occasions since 1982 till 2002, and ...

on 2 June 2001. The Observatory was dedicated to the nation on 29 August 2001.

Dark-sky preserve and astrotourism

Hanle Dark-sky preserve

IAO-Hanle-high energy gamma-ray telescope-AtNight

In September 2022, the area surrounding Hanle became India's first

dark-sky preserve A dark-sky preserve (DSP) is an area, usually surrounding a park or observatory, that restricts or reduces light pollution or maintains and protects naturally dark night skies. Different terms have been used to describe these areas as national or ...

. The Hanle site is deemed to be excellent for visible, infrared and

submillimeter Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy that is conducted at submillimetre wavelengths (i.e., terahertz radiation) of the electromagnetic spectrum. Astronomers plac ...

observations throughout the year. Specifically, the observation conditions yield about 255

spectroscopic Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectrosc ...

nights per year, approximately 190 photometric nights per year, and an annual rain-plus-snow precipitation of less than 10 cm. In addition, there are low ambient temperatures, low humidity, low concentration of atmospheric aerosols, low atmospheric water vapour, dark nights, and low pollution. The preserve extends to the 6 hamlets of Hanle revenue village—Bhok, Dhado, Punguk, Khuldo, Naga, and Tibetan Refugee habitation within 1073 sq km

Changthang Wildlife Sanctuary The Changthang Wildlife Sanctuary (or the Changthang Cold Desert Wildlife Sanctuary) is a high-altitude wildlife sanctuary located in the Ladakhi adjunct of the Changthang plateau in the Leh district of the Indian Union Territory of Ladakh. It ...

in Changthang plateau. The northern, southern, eastern, and western extremities of the preserve are between 19.6 km and 22 km from the observatory.Hanle India's first dark sky reserve
accessed 5 June 2023. The darkness of the night sky is classified on the

Bortle scale The Bortle dark-sky scale (usually referred to as simply the Bortle scale) is a nine-level numeric scale that measures the night sky's brightness of a particular location. It quantifies the astronomical observability of celestial objects and the ...

from 1 ("excellent," i.e., extremely dark) to 9 ("inner-city sky," i.e., partially dark). Hanle is categorised as an excellent dark astronomical site with Bortle colour key "Black." The dark sky is important for the conservation of

nocturnal animals ''Nocturnal Animals'' is a 2016 American neo-noir psychological thriller film written, produced, and directed by Tom Ford in his second feature, based on the 1993 novel '' Tony and Susan'' by Austin Wright. The film stars Amy Adams, Jake Gylle ...

and ecology. To minimize light pollution and to ensure dark skies, Hanle preserve has many restrictions such as lights being indoors only in certain places, mandatory light-blocking curtains on windows and doors, street light colors limited to yellow, no high-beam headlights on vehicles, no vehicle movements at night, and more.India’s new tourism boom is in the sky. Uttarakhand to Andamans, stargazing on the rise
The Print, 5 June 2023. To avoid

altitude sickness Altitude sickness, the mildest form being acute mountain sickness (AMS), is a harmful effect of high altitude, caused by rapid exposure to low amounts of oxygen at high elevation. People's bodies can respond to high altitude in different wa ...

, tourists must acclimatize for a day or two at Hanle (at 4500 m elevation) or Leh.

Astrotourism

There are many astrotourism locations in India, ranging from Ladakh,

Himachal Pradesh Himachal Pradesh (; Sanskrit: ''himācāl prādes;'' "Snow-laden Mountain Province") is a States and union territories of India, state in the northern part of India. Situated in the Western Himalayas, it is one of the thirteen Indian Himalayan ...

Uttarakhand Uttarakhand (, ), also known as Uttaranchal ( ; List of renamed places in India, the official name until 2007), is a States and union territories of India, state in North India, northern India. The state is bordered by Himachal Pradesh to the n ...

South India South India, also known as Southern India or Peninsular India, is the southern part of the Deccan Peninsula in India encompassing the states of Andhra Pradesh, Karnataka, Kerala, Tamil Nadu and Telangana as well as the union territories of ...

Andaman Nicobar Islands The Andaman and Nicobar Islands is a union territory of India comprising 572 islands, of which only 38 are inhabited. The islands are grouped into two main clusters: the northern Andaman Islands and the southern Nicobar Islands, separated by a ...

. Among these, Uttarakhand has the highest number of public and private night sky observatories, such as

Aryabhatta Research Institute of Observational Sciences Aryabhatta Research Institute of Observational Sciences (ARIES) is a research institute in Nainital, Uttarakhand, India which specializes in astronomy, solar physics, astrophysics and atmospheric science. It is an autonomous body under the ...

(ARIES) in Devasthal in

Nainital district Nainital district is a district in Kumaon division which is a part of Uttarakhand state in India. The headquarters is at Nainital. Nainital District is located in Kumaon Division, and is located in the lower Himalayas. Haldwani is the largest ...

. The Uttrakhand government is also setting up observatories at

Abbott Mount Abbott may refer to: People * Abbott (surname) * Abbott (given name), a list of people named Abbott or Abbot Places Argentina * Abbott, Buenos Aires United States * Abbott, Arkansas * Abbott, Mississippi * Abbott, Nebraska * Abbott, Texas * ...

in Champawat district,

Pithoragarh Pithoragarh ( Kumaoni: ''Pithor'garh'') is a Himalayan town with a Municipal corporation in Pithoragarh district in the Indian state of Uttarakhand. It is the largest hill town in Uttarakhand. Etymology "The district is named after its hea ...

Kausani Kausani ( Kumaoni: ''Kôsānī'') is a hill station and Village situated in Bageshwar district in the state of Uttarakhand, India. It is known for its scenery and its 300 km-wide panoramic view of Himalayan peaks like Trisul, Nanda Devi an ...

Jadhang Sang (Jadhang) is a small hilly village in Uttarkashi District, Uttarakhand, India, and claimed by Zanda County, Ngari Prefecture, Tibet, China. A tributary of the Jadh Ganga, itself an important tributary of the Bhagirathi River, flows throu ...

(or Jadung, under the Vibrant Villages programme), and Takula (in Nainital). In Uttarakhand, a startup named Starscapes also has private astrotourism observatories at

Bhimtal Bhimtal (Kumaoni language, Kumaoni: ''Bhīmtāl'') is a town and a nagar palika, near Nainital, Nainital city in Nainital district in the state of Uttarakhand, India. It is situated at an altitude of 1370 meters above sea level and is about 22 ...

, and astrovillage Benital in

Chamoli district Chamoli district is a district of the Uttarakhand state of India. It is bounded by China's Xizang Autonomous Region to the north, and by the Uttarakhand districts of Pithoragarh district, Pithoragarh and Bageshwar district, Bageshwar to the eas ...

. There are more than 100 planetariums in India.

Nehru Planetarium Nehru Planetariums are the five planetariums in India, named after India's first Prime Minister of India, Prime Minister, Jawaharlal Nehru. These are located in Mumbai, New Delhi, Pune and Bengaluru, plus there is a Jawahar Planetarium in Prayagr ...

is based in five locations at

Mumbai Mumbai ( ; ), also known as Bombay ( ; its official name until 1995), is the capital city of the Indian state of Maharashtra. Mumbai is the financial capital and the most populous city proper of India with an estimated population of 12 ...

New Delhi New Delhi (; ) is the Capital city, capital of India and a part of the Delhi, National Capital Territory of Delhi (NCT). New Delhi is the seat of all three branches of the Government of India, hosting the Rashtrapati Bhavan, New Parliament ...

Pune Pune ( ; , ISO 15919, ISO: ), previously spelled in English as Poona (List of renamed Indian cities and states#Maharashtra, the official name until 1978), is a city in the state of Maharashtra in the Deccan Plateau, Deccan plateau in Western ...

Bangalore Bengaluru, also known as Bangalore (List of renamed places in India#Karnataka, its official name until 1 November 2014), is the Capital city, capital and largest city of the southern States and union territories of India, Indian state of Kar ...

, and

Prayagraj Prayagraj (, ; ISO 15919, ISO: ), formerly and colloquially known as Allahabad, is a metropolis in the Indian state of Uttar Pradesh.The other five cities were: Agra, Kanpur, Kanpur (Cawnpore), Lucknow, Meerut, and Varanasi, Varanasi (Benar ...

. The

Kalpana Chawla Kalpana Chawla (March 17, 1962 – February 1, 2003) was an American astronaut and aerospace engineer who was the first woman of Indian origin to fly to space. Chawla expressed an interest in aerospace engineering from an early age and took engi ...

Planetarium is in

Jyotisar Jyotisar, on the bank of Jyotisar Sarovar wetland, is a Hindu pilgrimage site in the city of Kurukshetra in Haryana state of India. According to Hindu tradition, Krishna delivered the sermon of ''Bhagavad Gita'' – the doctrine of ''Karma'' ...

Kurukshetra Kurukshetra () is a city and administrative headquarters of Kurukshetra district in the Indian state of Haryana. It is also known as Dharmakshetra ("Realm of duty") and as the "Land of the Bhagavad Gita". Legends According to the Puranas ...

Haryana Haryana () is a States and union territories of India, state located in the northern part of India. It was carved out after the linguistic reorganisation of Punjab, India, Punjab on 1 November 1966. It is ranked 21st in terms of area, with les ...

. In 2023, India had more than 15 private observatories for astrotourism that came up in the last five years, many of which have their observatories in multiple locations. Astrostays, a startup, organises astrotourism trips to Pangong in Ladakh. In

Karnataka Karnataka ( ) is a States and union territories of India, state in the southwestern region of India. It was Unification of Karnataka, formed as Mysore State on 1 November 1956, with the passage of the States Reorganisation Act, 1956, States Re ...

, the Association of Bangalore Amateur Astronomers (ABAA) meets every Sunday at the Banglore Nehru Planetarium and the

Bangalore Astronomical Society The Bangalore Astronomical Society (BAS) is a society of amateur astronomers and other interested individuals, headquartered in Bangalore. The primary objective of the BAS is to promote and popularize Astronomy as a hobby and science. History Th ...

(BAS) organizes regular astrotours to the outskirts of cities and to remote locations in India. Starvoirs, a

Chennai Chennai, also known as Madras (List of renamed places in India#Tamil Nadu, its official name until 1996), is the capital city, capital and List of cities in Tamil Nadu by population, largest city of Tamil Nadu, the southernmost states and ...

-based startup, owns private observatories in nine places across the country, including

Rameshwaram Rameswaram (; also transliterated as Ramesvaram, Rameshwaram) is a municipality in the Ramanathapuram district of the Indian state of Tamil Nadu. It is on Pamban Island separated from mainland India by the Pamban channel and is about from ...

Chidambaram Chidambaram is a major town and municipality in Cuddalore district in the Indian state of Tamil Nadu, on the banks of the Vellar River where it meets the Bay of Bengal. It is the headquarters of the Chidambaram taluk. The town is believed to b ...

Kodanad Kodanad is a rural riverside village of Ernakulam district in Kerala, South India. It is 18 km from Angamaly. Kodanad is situated on the south bank of Periyar river, about 42 kilometers east of Kochi. The village is a major tourist destina ...

, the

Andaman Islands The Andaman Islands () are an archipelago, made up of 200 islands, in the northeastern Indian Ocean about southwest off the coasts of Myanmar's Ayeyarwady Region. Together with the Nicobar Islands to their south, the Andamans serve as a mari ...

, and

Nagaland Nagaland () is a States and union territories of India, state in the northeast India, north-eastern region of India. It is bordered by the Indian states of Arunachal Pradesh to the north, Assam to the west, Manipur to the south, and the Naga Sel ...

. The astrotourism potential in India is underutilised and underdeveloped. There are numerous places in India that could be developed, designated, and preserved as dark sky preserves. For example,

Madikeri Madikeri (), earlier called as Mercara is city and headquarters of Kodagu district in the Karnataka state of India. It is recognised as one of the world's eight "hottest hotspots" of biological diversity and is also a UNESCO World Heritage Site ...

Coorg Kodagu district () (also known by its former name Coorg) is an administrative district in the Karnataka state of India. Before 1956, it was an administratively separate Coorg State at which point it was merged into an enlarged Mysore State ...

is surrounded by coffee plantations and natural forests and rates 3 (rural sky) on the Bortle scale. Just as

Project Tiger Project Tiger is a wildlife conservation movement initiated in India to protect the endangered tiger. The project was initiated in 1973 by the Ministry of Environment, Forest and Climate Change of the Government of India. As of March 2025, there ...

has immensely helped the conservation of tigers, their surrounding ecology, and the reduction of carbon footprints, the issue of the conservation of dark s could help conservation of ecology and nocturnal animals, but there is very low awareness of this in India. The designation of dark sky preserve by the

International Dark-Sky Association DarkSky International, formerly the International Dark-Sky Association (IDA), is a United States–based nonprofit organization incorporated in 1988 by founders David Crawford, a professional astronomer, and Tim Hunter, a physician and amateu ...

(IDA) is a 3-year process identifying dark sky areas, preparing a development and conservation plan, and submitting a proposal to IDA for the designation. There is no nationwide plan to systematically develop more dark sky areas with mandatory lighting restrictions.

Facilities

The Observatory has several active telescopes. These are the 2.01-meter optical-infrared Himalayan Chandra Telescope (HCT), the GROWTH-India telescope, a Cassegrain telescope, and a High Altitude Gamma Ray Telescope (HAGAR). The HCT is remotely operated from Bangalore from the Centre for Research and Education in Science and Technology (CREST) using a dedicated satellite link.

Himalayan Chandra Telescope (HCT)

The Himalayan Chandra Telescope is a optical-infrared telescope named after India-born Nobel laureate Subrahmanyam Chandrasekhar.Pallava Bagla (7 January 2002)
India Unveils World's Highest Observatory
, National Geographic News, Retrieved 21 January 2011 It contains a modified Ritchey-Chretien system with a primary mirror made of ULE ceramic which is designed to withstand low temperatures it experiences. The telescope was manufactured by Electo-Optical System Technologies Inc. at Tucson, Arizona, USA. The telescope is mounted with 3 science instruments called the Himalaya Faint Object Spectrograph (HFOSC), the near-IR imager, and the optical CCD imager. The telescope is remotely operated via an

INSAT-3B INSAT-3B is an Indian communications satellite which was built by the Indian Space Research Organisation and operated by Indian National Satellite System. It is the first Geostationary satellite by India. Overview INSAT–3B is the first satell ...

satellite link which allows operation even in sub-zero temperatures in winter.Ravi Sharma (Volume 18 - Issue 20, 29 Sep - 12 Oct 2001), , ''Frontline''; Retrieved on 25 January 2011

GROWTH-India Telescope

The GROWTH-India telescope is a 0.7-meter wide-field optical telescope that had first light in 2018. It is the country's first fully robotic research telescope. It was set up as a part of the international GROWTH program, and has been widely used for

time-domain astronomy Time-domain astronomy is the study of how astronomical objects change with time. Said to have begun with Galileo's '' Letters on Sunspots'', the field has now naturally expanded to encompass variable objects beyond the Solar System. Temporal varia ...

. The telescope is operated jointly by

IIT Bombay The Indian Institute of Technology Bombay (IIT- Bombay or IIT-B) is a Public university, public research university and Institute of technology, technical institute in Powai, Mumbai, Maharashtra, India. IIT Bombay is mainly known for the hig ...

and the Indian Institute of Astrophysics.

Punjabi University, Patiala (Punjab) 24-inch Cassegrain telescope Observatory

In the 1980s, a Cassegrain telescope was installed at a height in a huge dome on the observatory in the Punjabi University, Patiala campus. The Department of Physics, Punjabi University, Patiala is the only department in northern India with this unique facility.

IIA-Washington University Cassegrain telescope

Since 2011, the Indian Institute of Astrophysics (IIA) has collaborated with the McDonnell Center for the Space Sciences of

Washington University in St. Louis Washington University in St. Louis (WashU) is a private research university in St. Louis, Missouri, United States. Founded in 1853 by a group of civic leaders and named for George Washington, the university spans 355 acres across its Danforth ...

to operate two 0.5-meter

Cassegrain telescope The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas, the main characteristic being that the optical path folds back onto itself, relative to th ...

s to monitor

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

. One of the observatories is established in Hanle. The facilities, 180 degrees apart in

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

, are together to be called the Antipodal Transient Observatory (ATO).

High Altitude Gamma Ray Telescope

IAO-Hanle-high energy gamma ray telescope-UnderRainbow

The High Altitude Gamma Ray Telescope (HAGAR) is an atmospheric Cerenkov experiment with 7 telescopes set up at Hanle in 2008. Each telescope has 7 mirrors with a total area of . The telescopes are deployed on the periphery of a circle of radius with one telescope at the center. Each telescope has alt-azimuth mounting. A Himalayan

Gamma Ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

Observatory (HiGRO) was set up at Hanle in collaboration with

Tata Institute of Fundamental Research Tata Institute of Fundamental Research (TIFR) is a leading research Institute under the Department of Atomic Energy of the Government of India. It is a public deemed university located at Navy Nagar, Colaba in Mumbai. It also has a centres in ...

and

Bhabha Atomic Research Centre The Bhabha Atomic Research Centre (BARC) is India's premier nuclear research facility, headquartered in Trombay, Mumbai, Maharashtra, India. It was founded by Homi Jehangir Bhabha as the Atomic Energy Establishment, Trombay (AEET) in January 1954 ...

, Mumbai. The

Major Atmospheric Cerenkov Experiment Telescope Major Atmospheric Cerenkov Experiment Telescope (MACE) is an imaging atmospheric Cerenkov telescope (IACT) located near Hanle, Ladakh, India. It is the highest (in altitude) and second largest Cerenkov telescope in the world. It was built by ...

(MACE) was set up here in December 2012. The Experiment has a collector which can collect gamma rays from space. The facility is a result of an initiative led by

in collaboration with the

, Indian Institute of Astrophysics,

and Saha Institute of Nuclear Physics,

Kolkata Kolkata, also known as Calcutta ( its official name until 2001), is the capital and largest city of the Indian state of West Bengal. It lies on the eastern bank of the Hooghly River, west of the border with Bangladesh. It is the primary ...

. The facility cost in 2011 was Rs. 400 million. As of 2011, it was the first and only such facility in the

Eastern Hemisphere The Eastern Hemisphere is the half of the planet Earth which is east of the prime meridian (which crosses Greenwich, London, United Kingdom) and west of the antimeridian (which crosses the Pacific Ocean and relatively little land from pole to p ...

. The telescope was fabricated by the Electronics Corporation of India and was installed at the IAO in June 2014. This telescope became the second-largest gamma-ray telescope in the world and the world's largest telescope at the highest altitude.

Center for Research and Education in Science and Technology

The Center for Research and Education in Science and Technology (CREST) is situated 35 km to the northeast of

near

Hoskote Hoskote (historically known as Ooscota or Ooscata) is a taluk or city in Bangalore Rural District, India. Headquartered at the Hoskote town, it consists of five hoblis - Kasaba , Anugondanahalli, Jadigenahalli, Nandagudi and Sulibele. There ...

town. The Center houses the control room for the remote operations of the 2-meter Himalayan Chandra Telescope (HCT) at the Indian Astronomical Observatory, Hanle, and the HCT data archive. The operations are controlled using a remote satellite link.

References

External links

* Official Website
Indian Astronomical Observatory

2-m Himalayan Chandra Telescope with the 50-cm Antipodal Transient Observatory in the background

Bangalore scientists, techies to help build largest telescopes
{{Portal bar, India, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science Astronomical observatories in India Space programme of India Indian Institute of Astrophysics Buildings and structures in Ladakh Leh district Science and technology in Ladakh 2001 establishments in Jammu and Kashmir