India's Aditya L1 launched successfully; starts 125-day journey towards Sun

India successfully launched its first observation mission to the Sun, Aditya-L1, from the launch pad at Sriharikota at 11:50 am on Saturday. The mission comes days after the country made history by becoming the first country to land on the Moon's south pole and the fourth country to soft-land on the lunar surface.

Named after the Sun God in Hindu mythology, Aditya-L1 was launched by a 44.4-metre tall Polar Satellite Launch Vehicle (PSLV), India's reliable workhorse in the space sector. After around one hour and four minutes, approximately at 12:54 pm, Aditya-L1 was successfully injected into an intermediate orbit, a first step towards its 125-day journey. Of the 91 launches conducted by the Indian Space Research Organisation (Isro), 59 used PSLV rockets. Though the actual cost of the mission is unknown, the government allotted around $48 million for it.

"Congratulations, the Aditya L1 spacecraft has been injected," said Isro chairman S Somnath, announcing the launch's success. This was the first time that the upper stage of the PSLV has conducted two burning sequences. "After some Earth manoeuvres, Aditya L1 will start its journey towards the L1 point now," he added.

The mission is expected to take 125 days to reach a halo orbit around Lagrangian point 1 (L1) of the Sun-Earth system, which is located approximately 1.5 million km from Earth. This distance represents only 1 per cent of the total 150 million km between Earth and the Sun. Through the mission, Isro will enter into the elite league of players, including the United States, Japan, the European Space Agency (ESA) and Germany, to have a separate mission to study the Sun. In 2021, Nasa made history by becoming the first human-made object to reach as close as 7.5 million km near the Sun, becoming the first to fly through the corona, the outer atmosphere of the Sun.

"While the whole world watched this with bated breath, it is indeed a sunshine moment for India," said Jitendra Singh, Minister of State for the Ministry of Science and Technology. The two key scientists who were leading the mission were project director Nigar Shaji and mission director Biju S R.

The spacecraft is planned to be placed in a halo orbit around Lagrangian point 1 (L1) of the Sun-Earth system, which is about 1.5 million km from Earth. A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the Sun without any occultation or eclipse. This will provide a greater advantage of observing solar activities continuously.

The spacecraft carries seven payloads to observe the photosphere, chromosphere and the outermost layers of the Sun (the corona) using electromagnetic and particle detectors. Using the special vantage point of 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.

The suite of Aditya L1 payloads is expected to provide crucial information to understand the problems of coronal heating, Coronal Mass Ejection, pre-flare and flare activities, and their characteristics, dynamics of space weather, the study of the propagation of particles, and fields in the interplanetary medium.

Initially, the spacecraft was placed in a low Earth orbit. Subsequently, the orbit will be made more elliptical, and later, the spacecraft will be launched towards the Lagrange point L1 using onboard propulsion. As the spacecraft travels towards L1, it will exit the Earth's gravitational Sphere of Influence (SoI). After exiting from SoI, the cruise phase will start, and subsequently, the spacecraft will be injected into a large halo orbit around L1.