On September 28, 2025, India celebrated the 10th anniversary of AstroSat, its first dedicated multi-wavelength space observatory. Launched on September 28, 2015, aboard a PSLV-C30 rocket from the Satish Dhawan Space Centre, AstroSat has surpassed its initial design life of five years and continues to provide valuable scientific data across ultraviolet, visible, and X-ray bands.

AstroSat's Capabilities and Mission Objectives

AstroSat is designed to observe celestial sources simultaneously in X-ray, optical, and UV spectral bands. This unique capability enables scientists to study a wide range of astrophysical phenomena, from nearby solar system objects to distant stars and galaxies. The mission's primary scientific objectives include:

• Understanding high-energy processes in binary star systems containing neutron stars and black holes.
• Estimating magnetic fields of neutron stars.
• Studying star birth regions and high-energy processes in star systems beyond our galaxy.
• Detecting new, transient X-ray sources in the sky.
• Conducting sky surveys in the hard X-ray and UV bands.
• Performing broadband spectroscopic studies of X-ray binaries, active galactic nuclei (AGN), supernova remnants (SNRs), clusters of galaxies, and stellar coronae.
• Studying periodic and non-periodic variability of X-ray sources.

The satellite has five payloads: the Ultra Violet Imaging Telescope (UVIT), Large Area X-ray Proportional Counter (LAXPC), Cadmium-Zinc-Telluride Imager (CZTI), Soft X-ray Telescope (SXT), and Scanning Sky Monitor (SSM). These instruments allow AstroSat to observe the universe in the visible, ultraviolet, soft X-ray, and hard X-ray regions of the electromagnetic spectrum.

Key Discoveries and Achievements

AstroSat has made several significant contributions to our understanding of the universe. Some of its key achievements include:

• Resolving the Red Giant Star Puzzle: AstroSat's initial findings helped explain the unusual brightness of a red giant star observed in both ultraviolet and infrared light, resolving a two-decade-old puzzle.
• Detecting Extreme Ultraviolet Light from Distant Galaxies: AstroSat detected extreme ultraviolet light from a galaxy 9.3 billion light-years away, a feat that NASA's Hubble Space Telescope could not achieve due to AstroSat's lower background noise.
• Mapping Supernova Remnants: The space observatory contributed to mapping supernova remnants, aiding in the study of explosive stellar events.
• Black Hole Insights: It detected high-energy X-rays from binary star systems, leading to significant discoveries about black holes, including chaotic fluctuations in X-ray emissions from the black hole system Swift J1727.8-1613 during an energy burst.
• Gamma-Ray Burst Studies: AstroSat observations have led to studies of over 500 gamma-ray bursts. Its very first scientific result was a gamma-ray burst detection just hours after the instrument was powered on.
• Dwarf Galaxy Formation: AstroSat has provided insights into the formation of dwarf galaxies, witnessing star-forming complexes on the outskirts of a dwarf galaxy.
• Stellar Variability: The satellite's observations have shed light on the variability in the brightness of stars, providing insights into their evolution and behavior over time.
• Galaxy Cluster Dynamics: AstroSat's observations of galaxy clusters have provided invaluable data on their intricate dynamics, gravitational interactions, and the distribution of hot gases within these colossal cosmic structures.
• Detection of Coronal Explosion: The space mission detected a coronal explosion from Proxima Centauri, the nearest exoplanet-hosting star.

AstroSat's Impact and Legacy

AstroSat has fostered international collaboration, with data-sharing agreements benefiting the global scientific community. Over 3,400 researchers from 57 countries have registered to access its data. The mission has also popularized space science in India, bringing astrophysics research into 132 Indian universities.

Inspired by AstroSat's success, ISRO is considering developing a next-generation astronomy satellite to build upon its achievements and further enhance India's capabilities in space exploration and astronomical research. AstroSat has not only solidified India's position in space exploration and research but has also fostered international collaboration in the field of astronomy, paving the way for groundbreaking discoveries and continued exploration of the cosmos. The mission exemplifies multi-messenger astronomy, combining ultraviolet, optical, and multiple X-ray bands to simultaneously track stellar flares, black hole outbursts, and neutron star activity.