BENGALURU: On Chandrayaan-3’s Lander Module (LM) Vikram and rover Pragyan separating from the Propulsion Module (PM) on Thursday afternoon, Padma Shri awardee and former Indian Space Research Organisation (ISRO) scientist Mylswamy Annadurai said it is a great “milestone”.
“From now onwards, the lander’s activity comes into picture,” he said, adding that after today’s milestone, the next most exciting and nail-biting event would be the last 15-20 minutes of the lander’s journey to the designated landing site on the Moon’s south pole.
“It will take 20 to 30 minutes for the spacecraft to soft-land on the site. That would be an autonomous movement. Mission scientists at ISRO will programme it a day earlier, on August 22, but the final landing of Vikram will be autonomous,” said Annadurai, also known as India’s Moon Man. He was the programme director for India’s earlier moon missions - Chandrayaan 1 and Chandrayaan 2.
He explained that after the separation of the lander from the PM, the next major event will be on Friday, August 18, when four 800 Newton thrusters will undergo flight firing to take Vikram to the lower orbit. The final firing to lower the spacecraft from 30 km height from the lunar surface will happen on August 23 at 5.47 pm. The precision of the last orbit manoeuvre is critical.
The real activity will start when the velocity will be reduced to one to two metre per second before the lander soft lands at the proposed landing site on the Moon’s south pole. Giving details of the lander’s last leg of its journey to the Moon, Annadurai said the velocity at the starting of the landing process is almost 1.68 km per second, but this speed is horizontal to the surface of the moon. While the horizontal velocity is being brought down, the vertical velocity will come up because of lunar gravity. That will also be reduced by proper orientation. The touchdown velocity of the spacecraft will be one metre per second,” said the famous aero-space engineer.
ISRO Chairman S Somanath had recently said the most critical part of the landing is the process of bringing the velocity of the lander from 30 km height to the final landing. “It’s a trick we have to play. We have done a lot of simulations. It is here where we had the problem last time (Chandrayaan-2),” he had explained.
Speaking about Luna 25 - Russia’s first lunar lander, which is scheduled to land around Chandrayaan-3, Annadurai said that Luna25 is exclusively for landing at the moon. “It doesn’t have a rover. There’s a possibility that the landing site may get polluted because of the thruster plumes,” he said.
“In Chandrayaan-3, its six-wheeled rover (Pragyan) will move away from the lander after it soft lands on the Moon between 100 metres and 500 metres marking the beginning of 14 Earth Day planned scientific exploration. It will be an undisturbed lunar site,” said the Moon Man.