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India’s First Solar Mission Aditya-L1 to Observe the Sun

An exciting journey to the sun

by Krati Soni

Aditya-L1 spacecraft is India’s first space-based observatory mission. This ambitious project of the Indian Space Research Organisation (ISRO) is aimed to observe the Sun. Aditya-L1 will be at Lagrange point L1, which is about 1.5 million kilometres away from Earth.

Why study Sun?

The sun is the nearest star and influences the weather and normal functioning of Earth and its satellites. Sun’s energy is released in two ways. It can either be a usual flow of light that makes life possible on our planet or can be violent which disturbs the magnetic field of the solar system. By studying the sun, we can get insight into the sun’s atmosphere and its magnetic fields and how its changing conditions can influence Earth,  and even space. Thus, studying sun is a significant investment. 

The position of 5 Lagrange points of Sun and earth system

Lagrange points L1 ,L2, L3, L4, and L5

Image credit: NASA

What is L1?

Aditya-L1 is planned to be placed in a halo orbit around the Lagrange point 1 (L1) of the Sun-Earth system. Lagrange points are points where the gravitational pull of the two large celestial bodies equals the necessary centripetal force required for a small object to move with them. For two body gravitational systems (here Sun and Earth), there are a total five Lagrange points denoted as L1, L2, L3, L4 and L5. The major advantage at L1 is constant sun exposure. The idea of spacecraft to be at Lagrange point L1 gives an uninterrupted view of the sun.

Aditya-L1’s Trajectory

Trajectory of Aditya-L1 from earth to L1

Trajectory of Aditya-L1

Image credit: prep

The 1,500 kg (3,300 lb) spacecraft will initially be in low earth orbit. Subsequently, after following an elliptical orbit it will be launched towards the Lagrange point L1 by using on-board propulsion. As Aditya-L1 travels towards L1, it will exit the earths’ gravitational Sphere of Influence (SOI). Subsequently, the spacecraft will be injected into a large halo orbit at L1. The total travel time from launch to reach L1 would take about four months.

“The spacecraft carries seven payloads to observe the photosphere, chromosphere and the outermost layers of the Sun (the corona) using electromagnetic and particle and magnetic field detectors. Using the special vantage point L1, four payloads directly view the Sun and the remaining three payloads carry out in-situ studies of particles and fields at the Lagrange point L1, thus providing important scientific studies of the propagatory effect of solar dynamics in the interplanetary medium”, says ISRO.

Schematic diagram of Aditya-L1 Payloads with parts labelled

Labelled payloads of Aditya-L1

Image credit: ISRO

The primary payload is the Visible Emission Line Coronagraph (VELC), designed and fabricated by the Indian Institute of Astrophysics, Bengaluru.

“No other solar coronagraph in space can image the solar corona as close to the solar disk as VELC can. It can image it as close as 1.05 times the solar radius. It can also do imaging, spectroscopy, and polarimetry at the same time, and can take observations at a very high resolution (level of detail) and many times a second,” Prof. Prasad said.

It is not understood how exactly the sun’s radiation affects the dynamics of the Earth’s atmosphere on a shorter as well as on longer time scale. The mission will obtain near simultaneous images of the different layers of the Sun’s atmosphere, which reveal how the energy may be channelled and transferred from one layer to another.

Thus the Aditya-L1 mission will enable a deep understanding of the dynamics processes of the Sun and address some of the outstanding problems in solar and heliophysics.

Launch of Aditya-L1 scheduled in August 2023

The Aditya-L1 mission will be launched by ISRO PSLV-XL(C56) rocket from Sathish Dhawan Space Centre SHAR (SDSC SHAR), Sriharikota. The launch is planned for August/ September 2023.

Aditya L1 shall be India’s first solar mission. The L1 point will provide us with the advantage of observing solar activities and its effect on space in real time. This five-year mission of Aditya-L1 shall provide us with important scientific studies of the propagatory effect of solar dynamics in the interplanetary medium. The mission will delve into layers of the sun which in-turn will assist us in the working of other suns in other galaxies.

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