Aditya-L1 Launched: The Indian Space Research Organisation (ISRO) launched Aditya-L1, India’s first space-based solar observatory to study the Sun, on Saturday, September 2, 2023, at 11:50 am IST. Aditya-L1 took off atop a PSLV-XL (Polar Satellite Launch Vehicle) rocket, from Satish Dhawan Space Centre, Sriharikota. This was the second launch from the Second Launch Pad at Satish Dhawan Space Centre. Also known as PSLV-C57, the mission marked the 59th flight of PSLV.
Aditya-L1’s journey towards the Sun will be a complex one, and will involve multiple phases. The spacecraft will reach its final destination about 125 days from launch.
Aditya-L1 will study the Sun because understanding the only star in the solar system will help scientists know more about other stars in the Milky Way galaxy.
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What is Aditya-L1’s final destination?
Aditya-L1’s final destination is a halo orbit around Lagrange point 1 (L1), which is located 1.5 million kilometres from Earth. This is approximately one per cent of the distance between the Sun and the Earth, which is 150 million kilometres. Therefore, Aditya-L1 will be located about 148.5 million kilometres from the Sun.
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Why has L1 been chosen as the destination for Aditya-L1?
Lagrange points are special points in space where the gravitational forces exerted by large masses are balanced, as a result of which the spacecraft placed in the vicinity of that region can save energy by using minimal fuel. There is an equilibrium because the gravitational forces exerted by the two large bodies will be equal to the centripetal force required by a small object to move with those bodies. This means that at L1, the gravitational forces exerted by the Sun and the Earth will be equal to the centripetal force required by Aditya-L1 to move with the Sun and the Earth. As a result, the forces will be balanced, and Aditya-L1 will simply hover in the halo orbit, causing it to save fuel.
Another huge advantage of L1 is that when placed there, Aditya-L1 will not witness any eclipses or occultations. As a result, the solar observatory will have an uninterrupted view of the Sun for the entirety of its mission life, which is five years.
What path will Aditya-L1 follow to reach its destination?
After being launched, Aditya-L1 will be placed in a circular low-Earth orbit. Then, the spacecraft will undergo three orbit-raising manoeuvres so that after each perigee burn, the orbit becomes more elliptical than the previous one. After the three orbit-raising manoeuvres, which will be performed using Earth’s gravity, are completed, Aditya-L1 will exit Earth’s gravitational sphere of influence (SOI).
Next, Aditya-L1 will enter the cruise phase, which is an important step because this stage will take the spacecraft towards the halo orbit around L1. In January 2024, Aditya-L1 is expected to inject itself into a halo orbit around L1. A halo orbit is neither circular or elliptical, but is stretched on both sides. The distance between the farthest points is 13 lakh kilometres.
Aditya-L1 will perform scientific experiments for five years.
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What are Aditya-L1’s scientific objectives?
The spacecraft is equipped with seven payloads, which are of two types: remote sensing and in-situ instruments. There are four remote sensing payloads and three in-situ payloads. The remote sensing payloads are spectroscopes, while the in-situ payloads include two particle analysers and one magnetometer.
Aditya-L1 will study the mechanisms occurring in the different layers of the solar atmosphere, the dynamics of coronal mass ejections and solar flares, the composition of coronal plasma, the effect of solar activities on space weather in real time, the energies of solar winds in different directions, and how solar particles affect the interplanetary medium.