ISRO’s ASTROSAT launch: India reaches for the stars

Astrosat is India's first dedicated multi-wavelength space observatory and was successfully launched on board the PSLV on 28 September 2015.

After the success of the satellite-borne Indian X-ray Astronomy Experiment (IXAE), which was launched in 1996, the Indian Space Research Organization (ISRO) approved further development for a full-fledged astronomy satellite, Astrosat, in 2004.

A large number of leading astronomy research institutions in India and abroad have jointly built various instruments for the satellite. Important areas requiring broad band coverage include studies of astrophysical objects ranging from the nearby solar system objects to distant stars, to objects at cosmological distances; timing studies of variables ranging from pulsations of the hot white dwarfs to active galactic nuclei with time scales ranging from milliseconds to few hours to days.

Astrosat is a multi-wavelength astronomy mission on an IRS-class satellite into a near-Earth, equatorial orbit by the PSLV. The 5 instruments on-board cover the visible (320–530 nm), near UV (180–300 nm), far UV (130–180 nm), soft X-ray (0.3–8 keV and 2–10 keV) and hard X-ray (3–80 keV and 10–150 keV) regions of the electromagnetic spectrum.

Astrosat was successfully launched on 28th September 2015 from Sriharikota on-board a PSLV-C30 vehicle at 10:00AM.

With the successful launch of the space observatory, Astrosat, the Indian Space Research Organisation has put India in a select group of countries that have a space telescope to study celestial objects and processes. The ability to simultaneously study a wide variety of wavelengths — visible light, ultraviolet and X-ray (both low- and high-energy) bands — has tremendous implications for scientists globally, particularly those in India. Though stars and galaxies emit in multiple wavebands, currently operational satellites have instruments that are capable of observing only a narrow range of wavelength band. Since the Earth’s atmosphere does not allow X-rays and ultraviolet energy from distant cosmic objects to reach ground-based telescopes, space observatories become important to unravel celestial mysteries. With Astrosat, Indian researchers will no longer have to rely on other space agencies for X-ray data, and scientists everywhere need no longer source data from more than one satellite to get a fuller picture of celestial processes. As in the case of Chandrayaan-1 and the Mars Orbiter Mission, Mangalyaan, the Astrosat telescope will have no immediate commercial or societal implications. But the instruments have been carefully chosen to allow scientists to pursue cutting-edge research. Chandrayaan-1 and Mangalyaan returned invaluable information, although they were launched several years after other countries sent satellites to the Moon and Mars. Given the uniqueness of Astrosat, it will enable Indian researchers to work in the frontier areas of high-energy astrophysics.

It is for the first time that a majority of the payloads for an Indian satellite has come from outside ISRO. In fact, ISRO has built just one of the five payloads for Astrosat; the rest comes from scientific institutions based in India. Two of the payload operation centres that would validate the data obtained by Astrosat will be located in the Mumbai-based Tata Institute of Fundamental Research that built three of the payloads, and one each in the Inter-University Centre for Astronomy and Astrophysics in Pune, and the Indian Institute of Astrophysics in Bengaluru that built one payload. This is in recognition of their contribution to the mission. Besides providing an opportunity to build world-class instruments, Astrosat will present an ideal platform for researchers in these institutions. As is the norm internationally, for a year the teams that built the payloads would have exclusive control over what is observed by the satellite. That singularly will be the biggest benefit to Indian researchers.

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