Engine calibration, landing site expansion for Chandrayaan-3: Lessons from 2019
India successfully launched Chandrayaan-3, its third lunar mission, on Friday.
At 2.35pm on Friday, the Indian Space Research Organisation (Isro) successfully launched Chandrayaan-3, India’s third lunar mission. On August 23, India hopes to be the fourth country to successfully land on the moon.

Isro has worked hard to ensure that the landing goes well; after all, four years ago, the second mission, Chandrayaan-2, was a success till that stage. Isro officials have termed that mission a “part failure” because while the lander and rover of the spacecraft did not complete its scientific objectives, the orbiter was injected into the lunar orbit and continues to provide key data and pictures from the moon.
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“We landed with a higher velocity—we call this a crash landing. But if you analyse the mission in its entirety, we have perfected the part of reaching up to the moon in earlier missions,” said an Isro official who did not want to be identified.
The failure analysis report prepared by Isro after Chandrayaan-2 highlighted that the five engines that were used for the reduction of velocity on the lander, developed a higher thrust than was intended.
The intention was for Vikram lander to lose most of its velocity by the time it was around 400m from the lunar surface and start the process of hovering above the intended landing site to ensure a soft vertical descent. The high velocity, however, caused it to crash on the moon’s surface.
“While this higher thrust was being achieved, the errors on the account of this differential started accumulating over a period. This is called the camera costing phase. During this period, the craft is ideally supposed to be steady to take pictures. If there are any errors, corrections can be made while it is happening, but we didn’t do that. We started correcting this only towards the end. When all these errors accumulated, which was slightly higher than we expected, the craft started making very fast turns. This hampered the ability of the craft to turn,” Somanath told HT in an interview before the launch.
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Chandrayaan-3 has four engines.
The Chandrayaan-2 lander was to land within a 500mx500m area. That meant the lander had no flexibility . In the case of Chandrayaan-3 the landing area has been increased to 4km x 2.5 km.
Isro has also ensured that the lander is now sturdier, with stronger legs, and a higher fuel capacity, to reduce the possibility of failure . It has worked to give the craft more flexibility to react to possible errors during the mission, even move around the landing area before landing.