Flashback to Chandrayaan-2: What went wrong with previous lunar mission

Chandrayaan-2 lander was launched on July 22, 2019 and was supposed to make a soft landing on the moon on September 7. However, the spacecraft crash-landed on moon's surface due to a software glitch

Chandrayaan-2 spacecraft was launched on July 22, 2019 from the Satish Dhawan Space Centre in Andhra Pradesh. The spacecraft consisted of a lunar orbiter, a lander, and the Pragyan rover, which was designed to study the variations in lunar surface composition, as well as the location and abundance of lunar water.

The craft reached the Moon's orbit on August 20, 2019 and began orbital positioning manoeuvres for the landing of the Vikram lander. The lander and the rover were scheduled to land on the near side of the Moon in the south polar region at a latitude of about 70 degree south. However, lander Vikram and rover Pragyaan crash-landed on the Moon’s surface during the early hours of September 7.

According to a failure analysis report submitted to the Indian Space Research Organisation (Isro), the crash of the spacecraft was caused by a software glitch.

What went wrong with Chandrayaan-2?

The Isro lost all contact with the Vikram lander on the day of the landing when it was around 335 metres (0.335 km) from the surface of the moon. The objective of the lunar mission was to make a soft landing on the surface of the moon.

The reason behind the crash landing of Vikram lander was that it tilted 410 degrees, instead of the planned 55 degrees.

When the lander tilted from its set trajectory, the scientists could do nothing. The velocity of the lander should have slowed down from 6,000 kmph to 0 kmph in four phases, but the space agency lost contact with it minutes before its touchdown.

At that time, the module was moving with a vertical velocity of 59 metres per sec (or 212 km/hr) and a horizontal velocity of 48.1 m/sec (or 173 km/hr). The lander was around 1.09 km from its designated landing spot on the moon.

Lander Vikram was supposed to lose most of its velocity when it reached 400 m from the surface of the moon, and should have been hovering above the intended landing site — set to make a soft vertical descent at “walking pace”. But due to the change in trajectory and the lack of speed reduction, the lander along with the moon rover, Pragyan, crash-landed on the surface of the moon.

The National Aeronautics and Space Administration (Nasa) and Isro attempted to establish communication with the lander for about two weeks. On September 14, 2019, Nasa's lunar reconnaissance orbiter (LRO) acquired images of the intended landing site but due to poor lighting of optical imaging, the images showed no signs of the lander. The LRO flew again on October 14, 2019 under favourable conditions but could not locate the lander.  

How is Chandrayaan 3 different from Chandrayaan 2?

Unlike Chandrayaan 2, the new spacecraft will not carry a rover aboard. It will carry a payload called 'spectro-polarimetry of habitable planet earth' (SHAPE), which the previous mission did not have.

SHAPE will study the spectral and polarimetric measurements of Earth from lunar orbit, which means that there are fewer chances of Chandrayaan 3 losing contact with the Isro and changing its trajectory, unlike the previous mission to the moon.