Loss of the Vikram Lander

Vikram lander impact site imaged by NASA LRO — The Vikram impact site and debris field imaged by NASA's Lunar Reconnaissance Orbiter. Image: NASA/GSFC/ASU

Vikram began its powered descent on 6 September 2019 at 20:08 UTC. The rough-braking phase went as planned, reducing velocity from about 1,680 m/s. During the fine-braking phase, at an altitude of about 2.1 km, the lander deviated from its intended trajectory; telemetry was lost moments before the expected touchdown at 20:23 UTC.

ISRO chairman K. Sivan confirmed that "it must have been a hard landing". The Failure Analysis Committee concluded the crash was caused by a software glitch: the lander's engines developed higher thrust than expected during camera coasting, accumulated errors exceeded permitted limits, and the guidance software's constraints on attitude correction rates prevented recovery in the time remaining.

Finding the crash site

NASA's Lunar Reconnaissance Orbiter imaged the landing zone, and on 2 December 2019 NASA confirmed the crash site had been located — credit for first spotting the debris went to Chennai-based engineer Shanmuga Subramanian, who identified fragments in publicly released LRO images. The debris field spread across roughly two dozen locations spanning several kilometres, centred about 750 m from the intended landing site.

From setback to success

The descent data from Vikram's failure was invaluable. ISRO redesigned the landing system for Chandrayaan-3 — stronger legs, larger fuel margins, a laser Doppler velocimeter, expanded landing zone and a "failure-based design" philosophy. On 23 August 2023, Chandrayaan-3's lander (also named Vikram) touched down flawlessly near the lunar south pole.

Source: Wikipedia — Chandrayaan-2