What makes ISRO's AstroSat a unique satellite?

AstroSat is India's first multi-wavelength space telescope


A few days ago, ISRO said in a tweet that scientists using the Indian space observatory, AstroSat, had made an intriguing discovery about a black hole system known as Swift J1727.8-1613. During an unusual burst of energy from this system, they noticed that the high-energy X-ray photons emitted were not following a regular, predictable pattern. Instead, the intensity of the X-rays was fluctuating in a chaotic, 'aperiodic’ manner. This finding could help scientists gain a deeper understanding of the complex processes occurring around black holes during such energetic events. 

All these findings were possible by ISRO's unique satellite and India’s first space telescope, AstroSat. Experts say it is a unique observatory designed to study celestial objects by observing their light in various wavelengths, including X-rays, visible light, and ultraviolet light. This multi-wavelength approach helps scientists gain a more comprehensive understanding of what is happening in space. 

After AstroSat was placed into orbit, the two solar panels that the observatory is fitted with were automatically deployed one after the other. The satellite is managed throughout its mission by the spacecraft control centre at the Mission Operations Complex (MOX) of ISRO Telemetry, Tracking and Command Network (ISTRAC), in Bengaluru. The science data collected by the five instruments on AstroSat is sent back to the ground station at MOX. This data is then processed, archived and distributed by the Indian Space Science Data Centre (ISSDC) located in Byalalu, near Bengaluru. ISRO, in collaboration with the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune. 

AstroSat, weighed 1,515 kg at launch, was sent into space on September 28, 2015. It was placed in a 650-kilometre high orbit, inclined at 6 degrees to the equator, by the PSLV-C30 rocket from the Satish Dhawan Space Centre in Sriharikota. The mission was expected to have a minimum useful lifespan of five years. 

“AstroSat’s special feature is its ability to observe different wavelengths of light from various space objects all at once using a single satellite. It can detect light from ultraviolet (both near and far), some optical, and X-rays ranging from 0.3 kilo-electronvolts (keV) to 100 keV. AstroSat stands out among global satellites because it can observe multiple wavelengths at the same time. For example, NASA’s Hubble Space Telescope mainly looks at near ultraviolet, visible and near-infrared light, while the Chandra X-ray Observatory focuses on X-rays. In contrast, AstroSat can see from far ultraviolet light all the way to a wide range of X-rays using its different instruments. This versatility makes it a valuable tool for a variety of astronomical research,” pointed out space expert Girish Linganna. 

He adds that the AstroSat has accomplished impressive things, such as studying high-energy activities in binary star systems, measuring the magnetic fields of neutron stars and exploring areas where stars are born and high-energy events occur beyond our galaxy. Additionally, it has detected new, short-lived X-ray sources in the sky and conducted a limited deep field survey of the universe in the ultraviolet spectrum. 

“AstroSat has already exceeded its planned five-year mission and shows potential for continuing its successful operations for at least another five years. It has observed around 400 sources, including polarisation in gamma-ray bursts (GRBs) and quasi-periodic oscillations. It has contributed to the search for X-ray counterparts of gravitational waves. Additionally, ISRO is considering the development of a next-generation astronomy satellite to build on AstroSat’s mission, which could enhance its current capabilities and provide even greater insights into the universe,” added Linganna. 


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