Bengaluru, August 16, 2023 (PTI) Chandrayaan 3 reached its final 153×163 km orbit around the moon on Wednesday, completing the series of manoeuvres to reduce the orbit and velocity of the spacecraft, the Indian Space Research Organisation (Isro) said. The lander-rover module will separate on Thursday from the propulsion module that carried it to the moon.

“It’s time for preparations as the Propulsion Module and the Lander Module gear up for their separate journeys,” the space agency said. After separation, the lander-rover module will prepare for the powered descent to the lunar surface scheduled for August 23.

The propulsion module, on the other hand, will remain in this final orbit for nearly three to six months, studying the spectro-polarimetric signatures of Earth from the lunar orbit using Spectro-polarimetry of Habitable Planet Earth (SHAPE). The experiment is designed to study the spectrum signatures of an inhabited planet – Earth – to help in the search for exoplanets and signs of life on them.

Chandrayaan 3 was launched on July 14 and reached the moon’s orbit 11 days ago.

The mission plans to achieve what its predecessor could not – softly land on the lunar surface close to the South Pole and rove the surface. Changes were made to the lander designs and mission specifications to ensure success. “Instead of a success-based design in Chandrayaan 2 we are doing a failure-based design in Chandrayaan 3 – we are looking at what all can go wrong and how to protect it,” Isro chairman S Somanath said earlier.

The lander has been given more ability to manoeuvre during the descent, the mission allows for a bigger 4 km x 2.4 km area for landing, more sensors have been added, one of the thrusters has been removed, and the legs of the lander have been made sturdier to allow for landing even at slightly higher velocity. More solar panels have also been added to ensure that the mission can go on even if the lander does not face the sun.

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More tests to see the capability of the lander in different situations were carried out to make Chandrayaan 3 more resilient.

Chandrayaan 2 was the first time India developed a lander and rover for one of its missions. Initially, the lander rover for the mission was to be developed by Russia. But Russia backed out after the failure of its Fobos-Grunt mission to one of Mars’s moons as similar technology was to be used.

However, the lander rover for Chandrayaan 2 crash-landed just 2.1 km from the surface of the moon.

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Explaining the reason for the failure of Chandrayaan 2 in its last leg, Somanath previously said that the five engines on the lander developed a slightly higher thrust than expected. As the programming on the lander did not allow for manoeuvres during the camera coasting phase – when it was essential to remain stable to click clear photographs of the landing site – the errors accumulated. When course corrections began, the spacecraft needed to turn very fast but its ability to turn was again limited by its software.

In addition, the spacecraft faced contradictory requirements of slowing down the velocity at which it was coming down but accelerated forward to reach the correct landing site. So, when it did land, it hit the ground with a higher velocity, Somanath had said.