ASTROSAT is the first dedicated Indian astronomy satellite. It was launched from Sriharikota, India on September 28, 2015. It is a multi-wavelength (Optical + UV + X-ray) astronomy space mission in a near-Earth, near-equatorial orbit. For more detail click : HERE .


  • 2 more rmf files are added on 14 June 2020
  • SXT Level2 pipeline version 1.4b released on 03 Jan 2019
  • SXT Camera Door Opened (First Light Seen) on 26 Oct 2015
  • SXT Telescope Door Opened on 15 Oct 2015
  • SXT switched on 30 Sep 2015
  • SXT aboard ASTROSAT launched on 28 Sep 2015

X-ray Telescope

Telescopes make clear images of cosmic objects by collecting large amount of light using mirrors and by focusing them on a detector at the focal point. In case of X-rays, the reflections from the mirrors have to be at very small (grazing) angles. So the geometry of an X-ray telescope is quite diffrent from that of a telescope which works in visible light.
One such geometry is the Wolter-I geometry, in which X-rays are reflected twice, first by a paraboloid mirror and then by a hyperboloid mirror, before being focused. Usually many nested mirror shells are used to increase the collecting area. The surface quality of the mirror is required to be very good (roughness of a few Angstroms) to avoid scattering, and therein lies a challenge.

Soft X-ray Telescope (SXT) on ASTROSAT

SXT is the first Indian X-ray telescope, which is a major milestone in Indian technological advancement. A schematic image of SXT is shown on the right. Its gold covered mirrors and other major components were built and assembled at the Department of Astronomy and Astrophysics (DAA) , Tata Institute of Fundamental Research (TIFR), Mumbai, India, except the focal plane camera with cooled charge-coupled device (CCD), which was built in collaboration with the University of Leicester, U.K., and for which the electronics was built entirely at DAA, TIFR, Mumbai.

Main Science Goals of SXT

  1. Studying matter in extreme conditions and testing fundamental laws of physics by observing neutron stars and black holes.
  2. Carrying out spectroscopy of hot thin plasmas in galaxies, clusters of galaxies, nuclei of active galaxies, quasars, supernova remnants and stellar coronae.
  3. Studying the physics of shocks and accretion disks, coronae, photo-ionized regions and their density, temprerature, ionization degree and elemental abundance.
  4. Studying low energy absorption and the nature of absorbers, for example whether these are cold (neutral) or warm (ionized).
  5. Studying soft X-ray excesses due to a blackboy emission in active galactic nuclei and in X-ray binaries in conjuction with other higher energy X-ray instruments.
  6. Carrying out spatially resolved spectroscopy of supernova remnants and clusters of galaxies.


If you are using the data from SXT, please refer the following two papers.

1. "In-orbit performance of SXT aboard AstroSat"
Kulinder Pal Singh, Gordon C. Stewart, Sunil Chandra, Kallol Mukerjee, Sanket Kotak, Andy P. Beardmore, Varsha Chitnis, Gulab C. Dewangan, Sudip Bhattacharyya, Irfan Mirza, Nilima Kamble, Vinita Navalkar, Harshit Shah, S. Vishwakarma, J. Koyande, 2016, SPIE, 9905-46.

2. "Soft X-ray Focusing Telescope Aboard AstroSat: Design, Characteristics and Performance"
K. P. Singh, G. C. Stewart, N. J. Westergaard, S. Bhattacharayya, S. Chandra, V. R. Chitnis, G. C. Dewangan, A. T. Kothare +33 coauthors, 2017, JApA, 38, 29.

In the Acknowledgement section in any publication utilising the SXT data, please add the following line:
"This work has used the data from the Soft X-ray Telescope (SXT) developed at TIFR, Mumbai, and the SXT POC at TIFR is thanked for verifying and releasing the data via the ISSDC data archive and providing the necessary software tools."

The SXT page was last updated on 19 APRIL 2021.