ISRO's Aditya-L1 mission to the Sun may launch as soon as 2020, says ISRO Chief

The mission, once called 'Aditya-1' was renamed 'Aditya-L1' after its final orbit was decided around the Earth-Moon L1 point.

India could launch its first ever mission to study the Sun – Aditya-L1 — as soon as 2020, the Indian Space Research Organization (ISRO) Chief K Sivan announced. There are a lot of things that scientists and astronomers are yet to learn about the Sun, he added, and the Aditya-L1 mission is hoping to address some of these questions while maintaining a direct line-of-sight with the Sun for the entire mission duration.

Once launched, the Aditya-L1 spacecraft will take up its position in what's called a 'halo orbit' around the Lagrangian Point 1 (L1). In all, there are five different "Lagrange points" — regions of space in systems like the Earth-Moon system or the Earth-Sun system, where the gravitational pull from both these bodies is balanced (equal). These Lagrange points are important in space exploration as they offer many benefits for orbiting satellites. The path such a satellite would follow around a Lagrange point is called a 'halo orbit'. These halo orbits, just like satellites that orbit the Earth or Moon, are periodic and predictable.

The mission, once called "Aditya-1" was renamed "Aditya-L1" after its final orbit around the L1 Lagrangian Point.

Solar Probe_NASA

The Aditya-L1 spacecraft will orbit 1.5 million km away from the Earth. While orbiting in Lagrangian point L1, it will not have any obstructions in viewing the Sun — not even during eclipses, the Chairman said. When the mission was first thought up, ISRO said that Aditya-L1 will carry just a single payload. This was later changed, and the mission now has six payloads in all.

However, the Visible Emission Line Coronagraph (VELC) that was once the first and only payload on the mission, remains the most important once since it will observe the solar corona. The corona is an aura of plasma (hot gas) that envelopes the Sun and other stars, which becomes visible to the naked eye during a total solar eclipse. It extends millions of kilometers into space.

llustration of the L1 point. Image courtesy: Wikipedia

Illustration of the L1 point. Image courtesy: Wikipedia

The satellite will observe the Sun's photosphere and chromosphere, and perform experiments as well. Other payloads on the satellite will measure the particle flux originating from the Sun and reaching the L1 orbit, while a magnetometer will measure the variation in magnetic field strength at the halo orbit. These payloads have to be placed outside the interference from the Earth’s magnetic field and hence could not have been useful in the low earth orbit of the previous Aditya-L1 mission.

NASA has also launched a $1.5 billion Parker Solar Probe that has gotten closer than any previous man-made object to the Sun.

(Also Read: All about the Aditya-L1: ISRO's upcoming satellite to unveil secrets of the sun)

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