Chandrayaan-3 landing: 17 minutes of terror for ISRO scientists

India's Chandrayaan-3 mission to the Moon is set to touch down on the lunar South Pole today at 6:04 PM IST, and the ISRO director has warned about the “17 minutes of terror” before the touchdown.

Chandrayaan-3 will make its soft landing on the Moon later today, August 23, but not before ISRO scientists go through the "17 minutes of terror". (REUTERS)

India's historic Moon mission, Chandrayaan-3, is set to touch down on the lunar South Pole today, August 23, at 6:04 PM IST. After the failure of Russia's Luna-25 mission which had similar ambitions, the world's eyes are on India. The mission, launched by the Indian Space Research Organization (ISRO), has three objectives - to carry out a safe and soft landing on the lunar surface, show the rover's roving capabilities, and conduct in-situ scientific experiments. However, two of them can only be achieved if the Vikram lander successfully touches down, and before that, it would have to pass through a 17-minute window of “terror”.

Chandrayaan-3: 17 minutes of terror

Speaking to ANI, the director of the Space Applications Center (SAC) at ISRO said that the last 17 minutes before the lander touches down on the lunar surface are extremely crucial, and could pose a risk to the soft landing, on which the whole mission depends.

During that period, the lander will have to carry out a series of maneuvers, including altitude adjustments, firing of thrusters, scanning the surface for any obstacles, and more.

Desai said, “We will have to retrofire the thruster engine, so that the lander de-accelerates to 0 when it makes the soft landing. We have installed four thruster engines in the lander module. From an altitude of 30 kilometers, the lander will come down to 7.5 kilometers and then to 6.8 kilometers.”

A few days ago, ISRO Chairman S Somnath highlighted that reducing its velocity from its current 30-kilometer altitude to the final landing will be a crucial aspect of the mission, along with the lander's ability to reorient itself from horizontal to vertical.

Next, two of the four engines will be shut off with the Moon's gravity also coming into play. The remaining engines will be used as reverse thrust for landing. “From 30 kilometers, the lander's speed will be less by four times to 350 meters per second at an altitude of 6.8 kilometers”, Desai added.

The Vikram lander will then make its descent till it will be just 800 meters from the lunar surface and will then hover until it decides on a site for its landing. Its Lander Hazard Detection and Avoidance Camera (LHDAC) will survey the landing zone and check for any obstacles in the vicinity.

“The entire process will take place in 17 minutes and 21 seconds. If the lander moves a bit sideways to land on the suitable site, the maximum site, time taken will be 17 minutes and 32 seconds. This '17 minutes of terror' is very critical for us”, Desai said.

If all goes well, Chandrayaan-3's Vikram lander will touch down on the lunar surface today, August 23 at 6:04 PM IST. Be sure to check our live coverage of the Chandrayaan-3 landing.