‘Made in India’ spectrograph commissioned on Devasthal Optical Telescope

Such spectroscopes were so far imported from abroad involved high costs. The ‘Made in India’ optical spectrograph, named as Aries-Devasthal Faint Object Spectrograph & Camera (ADFOSC), designed and developed by Aryabhatta Research Institute of observational sciences (ARIES), Nainital, an autonomous institute of Department of Science and Technology (DST), is about 2.5 times less costly compared to the imported ones and can locate sources of light with a photon-rate as low as about 1 photon per second.

The spectroscope, the largest of its kind among the existing astronomical spectrographs in the country, has been successfully commissioned on the 3.6-m Devasthal Optical Telescope (DOT), the largest in the country and in Asia, near Nainital Uttarakhand.

This instrument, a backbone of the 3.6-m DOT for observations of extremely faint celestial sources, uses a complex arrangement of several lenses made of special glasses, polished to better than 5-nanometer smoothness to produce sharp images of the celestial sky. Photons coming from distant celestial sources, collected by the telescope, are sorted into different colours by the spectrograph and are finally converted into electronic recordable signals using an in-house developed Charge-Coupled Device (CCD) camera cooled to an extremely low temperature of (-) 120 oC. The total cost of this instrument is nearly Rs4 crore.

The project was undertaken by a team of scientists at ARIES led by Amtesh Omar along with a technical and scientific team that researched and developed various optical, mechanical, and electronics subsystems of the spectrograph and camera. The spectrograph is currently being used by astronomers from India and abroad to study distant quasars and galaxies in a very young universe, regions around supermassive black-holes around the galaxies, cosmic explosions like supernovae and highly energetic Gamma-ray bursts, young and massive stars, and faint dwarf galaxies.

“The indigenous efforts to build complex instruments like ADFOSC in India is an important step to become ‘Aatmanirbhar’ in the field of astronomy and astrophysics,” said Prof. Dipankar Banerjee, Director, ARIES.

Expertise from various national institutes, organisations, including the Indian Space Research Organisation (Isro) and some micro-small-medium-enterprises, were involved to review and build parts of the instrument serving as an example of effective collaboration. With this expertise, ARIES now plans to commission more complex instruments such as spectro-polarimeter and high spectral resolution spectrograph on the 3.6-m Devasthal telescope in the near future.