The Indian Astronomical Observatory stands on Mt. Saraswati, Digpa-ratsa Ri, Hanle in south-eastern Ladakh union territory of India. Accessing the observatory, located near the Chinese border, requires a ten-hour drive from Leh Ladakh, the district capital of leh.
History
In the late 1980s a committee chaired by Prof. B. V. Sreekantan recommended that a national large optical telescope be taken up as a priority project. The search for the site of the observatory was taken up in 1992 under the leadership of Prof. 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, Bangalore and Hanle was inaugurated by the then Jammu and Kashmir Chief Minister Dr. Farooq Abdullah on 2 June 2001. The Observatory was dedicated to the nation on 29 August 2001.
Observation
The Hanle site is deemed to be excellent for visible, infrared and submillimeter observations throughout the year. Specifically the observation conditions yield about 255 spectroscopic 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.
Facilities
The Observatory has two active telescopes. These are the 2.01 meter optical-infrared Himalayan Chandra Telescope and a High Altitude Gamma Ray Telescope. The HCT is remotely operated from Bangalore from the Centre for Research and Education in Science and Technology using a dedicated satellite link.
Himalayan Chandra Telescope
The Himalayan Chandra Telescope is a 2.01 meters diameter optical-infrared telescope named after India-born Nobel laureateSubrahmanyam Chandrasekhar. 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 Himalaya Faint Object Spectrograph, the near-IR imager and the optical CCD imager. The telescope is remotely operated via an INSAT-3B satellite link which allows operation even in sub-zero temperatures in winter.
The High Altitude Gamma Ray Telescope is an atmospheric Cerenkov experiment with 7 telescopes setup in 2008. Each telescope has 7 mirrors with a total area of 4.4 square meters. The telescopes are deployed on the periphery of a circle of radius 50 meters with one telescope at the center. Each telescope has alt-azimuth mounting.
Center for Research and Education in Science and Technology
The Center for Research and Education in Science and Technology is situated 35 km to the northeast of Bangalore near Hoskote town. The Center houses the control room for the remote operations of the 2m Himalayan Chandra Telescope at the Indian Astronomical Observatory, Hanle, and the HCT data archive. The operations are controlled using a remote satellite link.
Upcoming facilities
The Indian Institute of Astrophysics is collaborating with the McDonnell Center for the Space Sciences of Washington University in St. Louis, US to operate two 0.5 meters Cassegrain telescopes to monitor active galactic nuclei. One of the observatories is to be established in Hanle. The facilities 180 degrees apart in longitude are together to be called the Antipodal Transient Observatory. A Himalayan Gamma Ray Observatory is being set up at Hanle in collaboration with Tata Institute of Fundamental Research, Mumbai and Bhabha Atomic Research Centre, Mumbai. This is currently in the advanced stage of commissioning and is expected to be functional by 2018. Major Atmospheric Cerenkov Experiment Telescope was expected to be set up here by December 2012. The Experiment expects to have a 21-meter collector which can collect gamma rays from space. The effort to establish the facility is led by Bhaba Atomic Research Center in collaboration with Tata Institute of Fundamental Research, Indian Institute of Astrophysics, Bangalore and Saha Institute of Nuclear Physics, Kolkata. The facility is estimated to cost Rs. 400 million. Once completed it will be the only such facility in the eastern hemisphere. As of June 2014 the telescope has been fabricated by the Electronics Corporation of India and is being installed at the IAO. Once installed, this Telescope will be the second largest gamma ray telescope in the world and the world's largest telescope at the highest altitude.
