The four phases of Chandrayaan-3’s soft landing— explained

India's lunar endeavour, Chandrayaan-3, is gearing up for a historic soft landing on the moon's surface, slated for 5:45 pm IST on August 23rd. The anticipated touchdown on the lunar landscape is expected to occur around 6:04 pm. If successful, India will carve its name in history as the first nation to achieve a lunar south pole landing.

Nonetheless, the venture carries an air of intrigue due to the memory of Chandrayaan-2's soft landing failure. This critical phase, dubbed as the "15 minutes of terror" by K Sivan, the former chairman of ISRO, remains at the forefront of curiosity.

Chandrayaan-3's soft landing will unfold in four distinct phases:

The mission will commence with ISRO's command from Bengaluru, instructing the lunar lander Vikram, positioned at an altitude of 30 km above the moon's surface, to transition from a horizontal to a descending orientation. This descent, occurring at a velocity of 1.68 km per second, will span 690 seconds.

Phase 2: As the lander approaches a height of 7.4 km from the moon's surface, it will transition from a horizontal to a vertical position, further reducing its speed. This maneuver is projected to take approximately 10 seconds.

Phase 3: The final and most delicate braking phase will see the lander fully assume a vertical position while covering a distance of 28.52 km to the designated landing site, ultimately reducing its velocity to zero. This phase stands as the riskiest, as it mirrors the stage at which Chandrayaan-2 lost control and met its unfortunate end.

Phase 4: When the lander nears the landing site, it will conduct crucial tests to ascertain the presence of obstacles. It will then decide whether to proceed with the planned landing or relocate to a safer spot.

Chandrayaan-3 will target a landing site similar to its predecessor's, chosen due to its potential water presence, as identified by Chandrayaan-1.

In essence, these final 15 minutes of the mission carry immense significance. The lander, Vikram, must execute precise engine firings at specific altitudes, utilising just the right amount of fuel to achieve a successful landing. Remarkably, Vikram will navigate this critical phase autonomously, as ISRO's control from Earth will be limited.

Upon a successful landing, images captured by the onboard cameras will be transmitted to Earth. However, ISRO has noted that unfavourable conditions may prompt a delay in the touchdown until August 27th.