Explained: How Chandrayaan-3 Could Launch India Into Exclusive League

When the rocket carrying the Chandrayaan-3 mission lifts off from Sriharikota tomorrow afternoon, India will look to build on the spectacular success of the first mission - which confirmed the presence of water molecules on the Moon - and hope to avoid the mistakes of the second, when the lander crashed on the lunar surface. 

India's Moonshots

Chandrayaan-1, India's maiden mission to the Moon, launched in October 2008 and remained operational till August 2009. It changed humanity's understanding of the celestial body by confirming the presence of water molecules on the lunar surface using its Moon Impact Probe. 

The next mission, Chandrayaan-2, launched in July 2019 and reached the Moon's orbit in August. The lander deviated from the planned trajectory while attempting to land on September 6 and suffered a hand landing. The orbiter, however, continues to function around the Moon in a very healthy state and has provided a lot of data to Indian Space Research Organisation (ISRO), which is expected to help with the Chandrayaan-3 mission.

Taking Flight Again

ISRO Chief S Somnath is confident that the Chandrayaan-3 mission, which is scheduled to lift off from Sriharikota at 2.35 pm tomorrow, could catapult India into the select list of nations that have achieved a controlled landing on the Moon. Currently, there are only three countries on that list - Russia, the United States and China.

The mission has three primary objectives: To demonstrate a safe and soft landing on the lunar surface; to demonstrate the rover's roving capabilities on the Moon; and to conduct scientific experiments.

The rocket being used is the Launch Vehicle Mark III (LVM-III), which was earlier called the Geosynchronous Satellite Launch Vehicle Mark III. 

The propulsion module will take the orbiter, the Vikram lander and the Pragyan rover to the lunar orbit. The lander will then softly touch down near the Moon's South Pole around August 23 and deploy the rover. 

Lessons Learnt

There are scientific experiments both on the lander and the rover and ISRO hopes to be able to carry out all of them, but the critical thing is to have a soft landing. 

Many changes have been made to the lander, with one of the big ones being that the legs have been made more robust. 

While Chandrayaan-2 had five engines on the Vikram lander, leading to anomalies, the lander on Chandrayaan-3 will have only four engines, which could give it more stability.

The software has been improved and rigorous testing of both the hardware and the software has been done. 

Mr Somanath said that the new mission has been designed to land successfully even if certain elements fail. Several scenarios, including sensor failure, engine failure, algorithm failure, and calculation failure were examined and measures developed to counteract them.

"The essential lesson is, in any space mission the focus should be on conditions of normality. So, how we address them and how we mitigate the possibilities of a failure in such an event," Mr Somanath said.

ISRO hopes to land Vikram at the same spot where the lander of Chandrayaan-2 - which also bore the same name - had attempted to touch down. The landing spot will be close to the South Pole of the Moon,  essentially because of the presence of water there. 

Gathering Data

The lander and rover are expected to have a life of one lunar day - equivalent to 14 Earth days - and will carry the same instruments as their predecessors on Chandrayaan-2. 

While the lander and rover will study the surface and atmosphere of the Moon, the orbiter will turn its focus to Earth to look at signatures of life on the Pale Blue Dot so that it can aid in the search of exoplanets (planets beyond the solar system) that may support life. 

The lander and rover will study the low-height atmospheric characteristics and electrostatic characteristics of the Moon. ISRO also hopes to be able to pierce a sensor into the surface of the Moon to a depth of about 10 cm and measure the thermophysical characteristics of the lunar regolith (the layer of unconsolidated solid material covering the bedrock).