Why ISRO is saying ‘17 minutes of terror’ for Chandrayaan 3? Senior official explains

India’s exciting moon mission, Chandrayaan-3, is getting closer to landing smoothly on the moon’s surface. The landing is set for Wednesday at 6:04 pm. However, the last 17 minutes before the landing are crucial and a bit worrisome.

As we anticipate Chandrayaan-3’s soft landing on the moon’s surface in less than a day, all eyes are on the final moments when the lander will gently touch down at the moon’s south pole. The head of ISRO (Indian Space Research Organisation) has called these moments the “17 minutes of terror.”

During these 17 minutes, a lot needs to happen just right. On August 23, the lander will start its descent from a height of 30 kilometres. It will be moving at a pretty fast speed of around 1.68 kilometres per second. The moon’s gravity will be pulling the lander towards it.

The director, Nilesh M Desai, explains the challenging parts: “We have to use the thruster engine to slow down the lander to a complete stop for a soft landing. The lander module has four thruster engines. It will come down from 30 kilometres to 7.5 kilometres, and then down to 6.8 kilometres.”

As Chandrayaan-3 prepares for a gentle touchdown on the moon’s south pole on Wednesday, a former advisor at ISRO, Dr. Surendra Pal, says that the lander is prepared even for a rough landing.

He explains that the lander can hover like a helicopter if the landing spot isn’t perfect. The moon’s south pole has many obstacles like boulders and craters, making the surface very uneven. The landing area has been expanded to 4 kilometres to increase the chances of a safe landing.

Dr. Pal mentions that if the lander can’t make a soft landing on Wednesday, there’s a backup plan for August 27. Even if two out of four thrusters work, the lander can still manage a landing. A lot of tests have been done, both on computers and real hardware, simulating the moon’s surface conditions.

A “soft landing” means the lander’s legs can withstand an impact of up to 3 metres per second. Dr. Pal believes the speed during landing will be around 1.86 metres per second. Even if one of the lander’s legs touches a slope, it can still land stably. The lander is built to handle some level of rough landing.

ISRO assures that the mission is on track, undergoing regular checks. The Mission Operations Complex (MOX) is buzzing with excitement. They’ve even shared images taken by the lander’s camera from 70 kilometres above the moon’s surface.

The landing process involves a careful sequence of steps. As the lander descends from 30 kilometres, its speed will decrease gradually to 350 metres per second at an altitude of 6.8 kilometres. Then, from 6.8 kilometres, it will descend further to 800 metres. Eventually, it will descend vertically to the lunar surface.

The entire process, from start to finish, takes about 17 minutes and 21 seconds. If the lander has to adjust its position a bit, the whole thing might take 17 minutes and 32 seconds. These critical minutes are dubbed the “17 minutes of terror” due to the high stakes and no room for mistakes.

The lander is expected to touch down on the moon’s south pole at 6:04 pm on Wednesday. If successful, India will join the US, Russia, and China as the fourth country to achieve this incredible feat.


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