Astrosat: India’s Unique Space Observatory
The launch of our first space observatory, the Astrosat, by the Indian
Space Research Organization (ISRO) has placed India in the elite club of four advanced
countries of the world that have their own space observatories, for probing heavenly
objects from the space-orbit into the open space. It is almost a unique feat because,
unlike similar missions by Europe and the U.S., it is a multi-wavelength
platform which affords a simultaneous observation of celestial objects across
different wavelengths, giving it a total perspective.
ISRO’s
most trusted rocket and workhorse launch vehicle, the PSLV-C30 carried this
satellite in the space to place it into a 650-km orbit following its takeoff
from the Satish Dhawan Space Centre, Shriharikota at 10 am on Sept 28, 2015.
The Astrosat is a major space-science feat of the ISRO and its mission envisages
an earth-orbiting scientific satellite with payloads capable of simultaneously
observing the universe in the visible, ultraviolet and X-ray regions of the
electromagnetic spectrum. The satellite is a multi-wavelength space observatory
, which makes it unique in the world in space research. It carries five
payloads including Ultraviolet Imaging Telescope- UVIT, Large Area Xenon
Proportional Counter–LAXPC Soft X-ray Telescope, Cadmium Zinc Telluride Imager
and Scanning Sky Monitor SSM.
Hitherto, the Indian astronomers have had to rely
on alien resources for X-ray and ultraviolet data for want of our own space
observatory. But, now with the launch of the ASTROSAT-telescope,
it would provide a shot in the arm of the Indian astronomers for such space
observations. It is all the more rejoicing for us in India, as the ASTROSAT-telescope is quite unique. Unlike
most other telescopes, the five instruments (payloads) of ASTROSAT can observe
a wider variety of wavelengths—from visible light to the ultraviolet and X-ray
bands. Even in the X-ray band as well, it can study both low and high energy
X-ray regions of the electromagnetic spectrum, while most other satellites are
capable of observing only a narrow range of wavelength band. Besides,
the capability to cover the full spectrum of wavelength simultaneously is
another unique feature of the ASTROSAT.
Though it has taken nearly 20 years in
the making, since the day the idea of such a satellite was put forward, and
about 15 years since the idea was given a concrete shape, the final realization
of what promises to be a true astronomical observatory in the sky is almost so unique
in its concept and operation that it is expected to make a significant and
niche contribution to the important field of X-ray astronomy and the study of
the X-ray universe. The Astrosat is a well dedicated astronomy satellite and a
miniature version of the Hubble, the US-European joint space observatory that
has discovered new galaxies and improved our understanding of the universe. The
Astrosat is the fourth in space, after the Hubble, Russia’s Spektr R and Suzaku
of Japan. It was initially planned for 2005 but it got delayed by a decade. However,
our scientific community has struggled hard to build it up to date with utmost precision
which such instruments need for such operations. So, delay does not matter.
The Astrosat is meant for
studying objects in the deep sky. It can make observations in ultraviolet,
optical, visible, low and X-ray wavelengths simultaneously. It will study
stars, quasars, pulsars, supernova remnants, black holes and active galactic
nuclei. The
instruments on board and spreading across ultraviolet and X-ray wavelengths,
will be capable of studying black holes, neutron stars, quasars, white dwarfs
and pulsars in space.
The Indian Space Research Organization (ISRO)
has also achieved a significant milestone in commercial satellites launch
segment as its trusted workhorse launch vehicle PSLV-C30 launched not only
the Astrosat, but, along with that, six other foreign satellites have also been
put into space from SHAR Range on September 28.
With this launch, ISRO would be crossing the
half-century mark in terms of launch of commercial satellites ever since
it launched the first ever satellite for a foreign customer on May 26, 1999 by using
the PSLV-C2. It is for the first time that
India has launched a US satellite. The US satellites are
the first from that country to be launched from India since the two countries
signed a technology safeguards agreement in 2009. The scientific objectives of ASTROSAT mission
are:
(i)
To understand high energy processes in binary
star systems containing neutron stars and black holes.
(ii)
To estimate magnetic fields of neutron stars.
(iii)
To study star birth regions and high energy
processes in star systems lying beyond our galaxy.
(iv)
To detect new briefly bright X-ray sources in
the sky.
(v)
To perform a limited deep field survey of the
Universe in the Ultraviolet region.
The five payloads of ASTROSAT are chosen to
facilitate a deeper insight into the various astrophysical processes occurring
in the various types of astronomical objects constituting our universe.
These payloads rely on the visible, Ultraviolet and X-rays coming from distant
celestial sources.
- The Ultraviolet Imaging Telescope (UVIT, capable of
observing the sky in the Visible, Near Ultraviolet and Far Ultraviolet
regions of the electromagnetic spectrum
- Large Area X-ray Proportional Counter (LAXPC, is
designed for studying the variations in the emission of X-rays from
sources like X-ray binaries, Active Galactic Nuclei and other cosmic
sources.
- Soft X-ray Telescope (SXT) is designed for studying how
the X-ray spectrum of 0.3-8 keV range coming from distant celestial bodies
varies with time.
- Cadmium Zinc Telluride Imager (CZTI), functioning in
the X-ray region, extends the capability of the satellite to sense X-rays
of high energy in 10-100 keV range.
- Scanning Sky Monitor (SSM) is intended to scan the sky
for long term monitoring of bright X-ray sources in binary stars, and for
the detection and location of sources that become bright in X-rays for a
short duration of time.
Moreover, the Astrosat is a
truly multi-institutional project, invoking collaborations even with foreign
institutions and agencies. Apart from ISRO, four other Indian institutions
involved in payload development are: Tata Institute of Fundamental
Research (TIFR), Indian Institute of Astrophysics (IIA), Inter-University
Centre for Astronomy and Astrophysics (IUCAA) and Raman Research Institute
(RRI). Two of the payloads were developed in collaboration with the Canadian
Space Agency (CSA) and University of Leiscester (UoL), UK. The International
customer satellites that have gone piggyback, along with the Astrosat, are the LAPAN-A2
- a microsatellite from National Institute of Aeronautics and Space-LAPAN,
Indonesia. LAPAN-A2 is meant for providing maritime surveillance using
Automatic Identification System (AIS), supporting Indonesian radio
amateur communities for disaster mitigation and carrying out Earth
surveillance using video and digital camera. The Second one, NLS-14 (Ev9)
is a Nan satellite from Space Flight Laboratory, University of Toronto
Institute for Advanced Studies (SFL, UTIAS), Canada. It is a maritime
monitoring Nan satellite using the next generation Automatic
Identification System (AIS). Four LEMUR nano satellites from Spire Global,
Inc. (San Francisco, CA), USA, are non-visual remote sensing satellites,
focusing primarily on global maritime intelligence through vessel tracking
via the Automatic Identification System (AIS), and high fidelity weather
forecasting using GPS Radio Occultation technology.
The Rs 178-crore
Astrosat has been hurled into space at lowest cost. It is a miracle that barely a year has passed since its first
interplanetary mission, Mangalyaan, entered the orbit of Mars, and ISRO has
crossed yet another important milestone. Scientifically the ASTROSAT is a very
different mission for ISRO from its other major missions and will add a new
dimension to its scientific capabilities. There are several advantages in having
a sky observatory. The atmosphere around the earth interferes with the signals
from space and changes their characteristics. So, what the instruments at earth
observatories receive are modified signals. These have to be adjusted to bring
in accuracy. But this space observatory would give us a truer picture.
