The Chandrayaan-3 landing module comprising Vikram (the lander) and Pragyan (the rover) has successfully separated from the propulsion module, marking a major milestone for the mission.”Landing module is successfully separated from the propulsion module. Landing module set to descend to a slightly lower orbit upon a de-boosting planned for tomorrow (August 18) at 4pm,” Isro said.

The seperation of manoevure was carried out by Isro a day after it guided the spacecraft — an integrated module with the propulsion module sitting on top of the landing module — into ‘an orbit of 153km x 163km, as intended’.

In his post-launch remarks on July 14, Isro chairman S Somanath had said the spacecraft’s altitude will be reduced to a 100km circular orbit and the landing module will get separated on August 17, which was a ‘nominal’ estimation.During Chandrayaan-2, which aimed for a 100km circular orbit with the last lunar-bound manoeuvre, the spacecraft was put into a 119km x 127km orbit. That was only off marginally from the initial plans but as intended going by estimations made closer to the last lunar manoeuvre.For Chandrayaan-3, a senior scientist had told TOI on July 15, the plan was to achieve a circular orbit, with an altitude of either 100km or 150km. “That will be decided closer to the date of the manoeuvre,” another scientist had said. And the orbit achieved Wednesday, Isro reiterated: “was as intended”.

Now, a series of de-boost manoeuvres will eventually put Vikram in an orbit where the Perilune (closest point to Moon) is 30km and Apolune (farthest point from Moon) is 100km. Again, this is a nominal estimation, and the final orbit achieved could vary marginally as was the case with Chandrayaan-2.Once the 30km x 100km orbit has been achieved, the most critical part of the landing, the process of reducing the velocity of the lander from 30km height to the final landing, as Isro chairman S Somanath had said earlier, will begin.Isro will also have to overcome the phase where the spacecraft’s horizontal orientation needs to change to a vertical one, before Vikram makes the final descent on August 23.

 

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