Even before the euphoria of Chandrayaan-3 moon-landing subsided, India’s space agency, ISRO, has pulled off another remarkable feat — placing the sun-observing spacecraft, Aditya L-1, in its halo orbit at the Lagrange-1 point. To steer a spacecraft into a specific spot 1.5 million km away from the earth is not a mean task, but Indian scientists have achieved that. Today, Aditya L-1 is not only basking in bountiful sunrays, but also in international adulation.

A Lagrange point is a location between two celestial bodies, where an object is subjected to equal gravitational pull by the two bodies, so that it ‘stays’ in place. As between any two celestial bodies, there are five Lagrange points between the earth and the sun, and L-1 is the closest to the earth, about 1 per cent of the distance to the sun. Aditya L-1 has been placed in a ‘halo orbit”, from where it will be peering at the sun 24x7 while also travelling along with the earth, as the earth moves around the sun. L-1 is the best place to put up a watchtower to keep an eye on the sun and today, happily, Aditya L-1 is there.

The Aditya L-1 mission is unique in many ways. Coming after Chandrayaan-3 moon landing and the got-it-right-the-first-time Mangalyaan (Mars) mission, the Aditya L-1 mission dispels any doubts about India’s ability to do complex space manoeuvres. While this fact has been well-recognised, somewhat under-appreciated is the scientific muscle that the India-made onboard instruments have. The Solar Ultra-violet Imaging Telescope (SUIT) will keep looking at the central disc of the sun — comprising the visible light-emitting photosphere and the chromosphere above the photosphere. The Visible Emission Line Coronagraph (VELC) will train its sights on the outer rim of the sun — the corona. Since both the instruments (developed at the Inter-University Centre for Astronomy and Astrophysics, Pune) will be looking at the same time, it is possible to study the impact of changes in disc of the sun on the corona. This is important.

Since the corona is the region that keeps throwing harmful things — stuff like charged particles, coronal mass ejections— some of which could rain down upon us, any knowledge of the impact of variations in the disc on the corona will be a sort of an early-warning to us of what might be coming from the sun. To look at it from another angle, Aditya L-1 has instruments that pick-up and analyse a big range of electromagnetic radiation from the sun. Some of Aditya’s instruments pick up everything from near-infra-red to soft X-rays and the others catch and analyse sun-spewed particles streaming into them. So, among themselves, the seven instruments can pick up and crunch on monstrous amounts of data. The Aditya L-1 mission is ISRO’s most complex ever, tougher than the three Chandrayaans and the Mangalyaan. In it lie anchored big expectations of the Gaganyaan mission, which will one day take an Indian to space.

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