ISRO Scientist Explains Why Chandrayaan-3 Soft Landing On Moon May Be Delayed

As the countdown for the touchdown of India's ambitious Chandrayaan-3 on the Moon's surface has started, ISRO Space Applications Centre Director Nilesh Desai has said that the landing might be postponed to August 27 in the event that health parameters of the lander module are found to be "abnormal"

"The lander will try to land on the Moon's surface from a height of 30km on August 23, and its velocity at that time will be 1.68 km per second. Our focus will be on reducing that speed because the Moon's gravitational force will also play its part," PTI quoted the official as saying in Ahmedabad.

"If we do not control that speed, there will be chances of a crash landing. If any health parameter (of the lander module) is found abnormal on August 23, then we will postpone the landing to August 27," he said.

ISRO had planned the soft landing of the Chandrayaan-3 spacecraft, which was launched on July 14 from Sriharikota, at 06.04 pm IST on August 23.

He expressed hope that scientists would try to make the lander module land on the lunar surface successfully. "The landing begins at 06.04 PM IST. Two hours before that, we will upload the commands. We will do an analysis of the telemetry signal and consider the conditions of the Moon. If any health parameter goes wrong, we will push it to August 27 and will try to land (on that day) if all goes well," he added.

Highlighting the significance of the last 17 minutes of the lander module's descent, he emphasized, "During the landing phase, the four-engine thrusters will engage to slow down the speed."

"When the lander is at a height of 800 metres from the lunar surface, running on two engines, the speed will reach zero. From 800 metres to 150 metres, it (lander module) will descend vertically," he said.

He mentioned that the data acquired through the sensors on the lander module holds great significance, as it will guide the selection of the landing site. "We have sensors that would transmit exact information about the speed and distance of the lander from the Moon's surface," he said.

"Planning (safe-landing on the lunar surface) has been done keeping various scenarios in mind. We hope to land at 70 degree latitude safely on the Moon's South Pole on August 23," he said.

Responding to another query, he said," A lot of upgrades have been made this time. Hardware systems are made robust. We will be successful (in soft landing on the lunar surface)," he said. In case the mission shifts to August 27, he said, "we have chosen another landing site which is 400 km away from the main landing site."

Chandrayaan-3 is a follow-on mission to Chandrayaan-2 to demonstrate end-to-end capability in safe landing and roving on the lunar surface. The lander and the rover have scientific payloads to carry out experiments on the lunar surface.