Chandrayaan-3 landing on August 27 if conditions are unfavourable: Isro

The Indian Space Research Organisation (Isro) has kept an alternative date for Chandrayaan-3 landing on August 27, if it will not be appropriate to land the Vikram module on August 23

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Chandrayaan-3 is set to make a soft landing on the moon at 6:04 pm on August 23.

The Indian Space Research Organisation (Isro) said it has successfully reduced the orbit of the Chandrayaan-3 mission's Lander Module (LM) on Sunday.

Chandrayaan-3 was launched on July 14, and the lander module of the spacecraft successfully separated from the propulsion module on August 17.

Alternative date for delayed landing

However, the Isro has kept an alternative date for Chandrayaan-3 landing on August 27 if it is not appropriate to land the Vikram module on August 23, according to a report in The Times of India (TOI).

Nilesh M Desai, director of the Space Applications Centre, said, "We have made full preparations for the August 23 soft landing, and we are hopeful that the landing will happen on that day. However on August 23, two hours before the landing, we will decide whether it will be appropriate to land it at that time based on the health of the lander module and conditions on the moon. If any factor appears not favourable, we will land the module on the moon on August 27. For that, too, we have made all preparations."

This time, Isro has strengthened the legs of the Vikram lander and has undertaken rigorous testing with the lander. After the recent crash landing of the Russian Luna-25 probe, Isro doesn't want to take any chances with the lander module after reaching the final stage of the Moon landing.

If the landing happens on August 27, the Isro may lose four Earth days for the operations of the rover and the lander.

Phases of descent

The horizontal velocity of 1.68 km/sec at the beginning of the landing process will be reduced to 358 m/sec horizontal velocity and 61 m/sec (about 220 km/h) vertical velocity in the ideal "rough braking phase" of 690 seconds, during which the lander will descend from an altitude of 30 km to 7.42 km, according to the TOI report.

During this time, the lander will travel a distance of 713.5 km towards the landing site.

At a height of 7.42 km from the surface, the lander will go into an "attitude hold phase" lasting around 10 seconds. The altitude will be reduced to 6.8 km and velocity to 336 m/sec (horizontal) and 59 m/sec (vertical).

The "fine breaking phase", the third phase of the landing process, will last around 175 seconds, during which the lander will move fully into a vertical position.

It will then travel 28.52 km to the landing site, and the altitude will come down to 800-1,000 m, and it will reach a nominal speed of 0 m/sec.