ISRO commences countdown for launch of maiden sun mission Aditya-L1

At 12.10 pm on Friday (Sept 1), the 23 hours 40 minutes countdown timer began ticking at the Satish Dhawan Space Centre spaceport in Sriharikota. At the end of this countdown, on Saturday noon, India's PSLV rocket in its XL variant will lift off from the first launchpad of India's spaceport, carrying the nation's maiden mission to study the sun.

Titled Aditya-L1, the craft will cover a distance of 1.5 million kilometres in spacein a span of approximately 125 days. The craft will be travelling to Lagrange Point 1 (L1), a vantage point from where it would have an unobstructed view of the sun.

While this is a mission to study the sun, it would be travelling only 1 per cent of the Earth-Sun distance, unlike crafts from NASA that have flown a few million miles in the vicinity of the giant star. The Earth-Sun distance is approximately 150 million kilometres.

The launch of Aditya-L1 comes barely 10 days after India soft-landed its Chandrayaan-3 craft (comprising a lander and rover) on the moon.

On Wednesday, the Indian space agency announced the completion of the launch rehearsal and crucial checks ahead of Saturday's high-profile launch of the nation's maiden sun-observing mission.

During a launch rehearsal, the entire process of the countdown is carried out in a simulated manner. The vehicle health checks, fuel filling processes, and monitoring of various technical parameters associated with the rocket and satellite are carried out in a simulated fashion.

The purpose of thecountdown is not just about the clock ticking away. Instead, the primary purpose of the countdown is to ensure that the specified tasks are carried out perfectly within the stipulated time period. A series of tasks and safety measures have to be undertaken in preparation for the launch and that is what happens during the countdown. The launch rehearsal is a simulation of this entire process.

According to ISRO, placing the spacecraft at the L1 pointprovides a greater advantage of observing the solar activities and their effect on space weather in real time. The spacecraft carries seven payloads to observe the photosphere, chromosphere and the outermost layers of the Sun (the corona) using electromagnetic particle and magnetic field detectors.

Using the special vantage point L1, four payloads will directly view the sun and the remaining three payloads will carry out in-situ studies of particles and fields, thus providing important scientific studies of the propagatory effect of solar dynamics in the interplanetary medium.

The Aditya L1 payloads are expected to provide the most crucial information to understand the problem of coronal heating, coronal mass ejection, pre-flare and flare activities and their characteristics, dynamics of space weather, propagation of particles and fields etc., ISRO said.

Notably, the launch of Aditya-L1 comes barely 10 days after ISRO successfully soft-landed the Chandrayaan-3 craft near the lunar south pole, thereby making India the first nation to do so.

With this successful soft-landing, India became the fourth nation to ever soft-land a craft on the lunar surface. The erstwhile Soviet Union, USA and China are the other countries.

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