Aditya-L1 — India's first dedicated solar observatory

Ten days after India landed on the Moon, the launch pads at Sriharikota were busy again. At 11:50 a.m. on 2 September 2023, a PSLV rocket climbed away from the Satish Dhawan Space Centre carrying Aditya-L1, named for Surya, the Sun god of Hindu tradition, on the country's first mission to study a star. The crowds in the viewing galleries were still riding the euphoria of Chandrayaan-3; now they watched ISRO turn, in less than a fortnight, from the Moon to the Sun.

The destination was a place rather than a world: Lagrange point 1, a gravitational balance point 1.5 million kilometres sunward of Earth where a spacecraft can hold position indefinitely with an uninterrupted view of the Sun, no eclipses and no nights. The 1,480-kilogram observatory carries seven instruments, four that stare at the Sun and three that taste the solar wind streaming past. Its crown jewel, the Visible Emission Line Coronagraph, blocks the solar disc with an internal occulter to manufacture a continuous artificial eclipse, revealing the corona that ground astronomers glimpse only during rare minutes of totality.

After a 126-day cruise, Aditya-L1 slipped into its halo orbit around L1 on 6 January 2024, a wide loop it traces roughly once every 178 days. From that vantage it works on the Sun's deepest puzzles, why the corona blazes at millions of degrees above a far cooler surface and how coronal mass ejections erupt, while serving a practical role as a sentinel: solar wind that washes over the spacecraft reaches Earth about an hour later, giving satellite operators and power grids advance warning of geomagnetic storms. India had joined the small club of nations keeping a permanent watch on our star.