How will Chandrayaan-3 land on the Moon? Expert breaks down the science

How will Chandrayaan-3 land on the Moon? Expert breaks down the science

The spacecraft has to glide through a tricky dance of gravity, orbits, and finally land safely. People in the space business call it the ‘seven minutes of terror,’ when the spacecraft is on its own and the engineers, and scientists are mere spectators like all of us.

Chandrayaan-3 Vikram landing will be conducted on August 23. (Photo: India Today/Vani Gupta)

Manish Purohit

New Delhi,UPDATED: Aug 22, 2023 10:49 IST

In the long journey of a spacecraft to another celestial body, there are several critical moments. Of them all, the most heart-pounding is when it makes the final journey to land. In those last minutes, everything hangs in the balance.

The spacecraft has to glide through a tricky dance of gravity, orbits, and finally land safely. People in the space business call it the ‘seven minutes of terror,’ when the spacecraft is on its own and the engineers, and scientists are mere spectators like all of us. The Indian space agency came face to face with it in 2019, during Chandrayaan-2.

With the Chandrayaan-3 mission on the cusp of attempting to soft-land on the Moon, here’s a runner on how it happens.

BREAKING DOWN CHANDRAYAAN-3 VIKRAM’S LANDING APPROACH

On August 23, during the final 18 minutes of its journey, Chandrayaan 3 is poised to etch history with a sequence of meticulously orchestrated manoeuvres.

To better understand this crucial procedure, imagine Chandrayaan-3 as a courageous space explorer, poised far away from its lunar landing site. It’s moving at a remarkable speed – similar to how a bullet train would feel if you were standing next to it.

As it orbits the Moon, the Vikram Lander, a part of Chandrayaan 3, finds itself 745.5 km away from the chosen landing spot, floating about 30 km above the Moon’s surface at a speed of 1.6 kilometers per second.

In the following 690 seconds, Chandrayaan 3’s engines will ignite, like tapping the brakes on a bicycle, gently easing it towards the Moon’s surface. This controlled slowdown will reduce its initial speed to a quarter, and the pull of the Moon’s gravity will guide Vikram Lander downwards at around 60 meters per second.

Chandayaan-3

Now, here’s the fascinating part: while slowing down, Chandrayaan-3 will turn slightly, similar to how we steer a bicycle. This graceful twist allows Chandrayaan-3 to align itself perfectly with the landing spot.

By the end of this procedure, it will be just 32 km away from the desired landing area, hovering approximately 7.5 km above the Moon’s ground. This is the moment to double-check that the landing spot is safe.

Isro has upgraded the process to make it faster and more accurate. During this phase, all of Vikram Lander’s sensors will be finely calibrated, ensuring everything is ready for the big moment.

Remember the challenge we faced during Chandrayaan-2?

Well, this time, Chandrayaan-3 is smarter. The part where we had a bit of trouble in 2019, during a phase where cameras were guiding the spacecraft, has been shortened to just 10 seconds, and the onboard error control system will be closely monitoring everything.

But why do it again if it caused a problem last time?

Well, this step is crucial.

Chandayaan-3

During this phase, the Moon’s terrain will be checked and confirmed for landing. Thanks to improved technology, this step will take less time but will be just as effective. After this, Vikram Lander will enter the Fine Braking Phase. Imagine it as the final check before something amazing happens.

During this phase, Vikram Lander will become vertical, hovering above the ground at a height of 800-1300 meters, right on the landing spot. Cameras will start taking pictures, sensors will gather data, and the onboard computer will start processing everything. This is the phase where crucial decisions will be made – like the finishing touches before creating history.

After hovering for about 12 seconds, the altitude will decrease to 150 meters. A special camera will check for any problems on the ground. If something seems off, Vikram Lander will move forward by 150 meters and try again.

But if everything’s good, the onboard computer will commit to the final descent. In the next 73 seconds, Vikram Lander will cover those 150 meters, making that moment unforgettable.

And then, finally, Vikram Lander will touch the lunar surface. The landing sensors will signal the onboard computer to awaken the systems. The Lander will power up fully, and the ramp for the rover named Pragyan will unfold.

Pragyan, like a little explorer, will roll out onto the lunar ground. And will be leaving footprints with Isro’s logo and India’s emblem on the Moon, a mark that will stay forever.

During this entire process, Vikram and Pragyan will take pictures of each other. These images will travel back to Earth through a special communication network that uses the Chandrayaan-2 orbiter, propulsion module, and Isro’s Deep Space Network Antennas.

Once it is confirmed that Vikram and Pragyan are safe and sound, Isro will begin different experiments to study the Moon’s soil and plasma environment. As part of this mission, a series of diverse experiments will be initiated to unravel the Moon’s secrets.

(This is an authored article by Manish Purohit, who has worked on several space fairing missions launched from India)

Edited By:

Sibu Kumar Tripathi

Published On:

Aug 22, 2023

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