How different is Vikram, the Chandrayaan-3 lander from Chandrayaan-2, and why? | India News

In September 2019, crores of Indians and thousands of others from across the world following Chandrayaan-2, were left disappointed after Isro could not complete the landing mission successfully, even as its orbiter is still very much alive and sending data. In fact, it will be used as part of Chandrayaan-3 too for relay of information.
Learning from this, Isro has implemented several improvements in Chandrayaan-3 to ensure success. And among several changes introduced in Chandrayaan-3, after its predecessor Chandrayaan-2 failed to soft-land on Moon in September 2019, significant are those introduced in Vikram, the lander.
TOI gives you a low down on what some of these changes are and why they were introduced:
Stronger Legs
Vikram will have stronger legs than in its previous avatar to enable withstanding landing at greater velocities than earlier.
“There are a lot of improvements on the lander. Basically, what were the deficiencies we were trying to overcome? One is the lander legs, which we expected could have withstood a higher velocity [during Chandrayaan-2]. So how much can we increase the velocity tolerance in the available structure? We have enhanced the landing velocity to 3m/second from 2m/second. That means even at 3m/sec, the lander will not crash or break [its legs],” Isro chairman S Somanath explained.
Another scientist who was part of Chanrayaan-2 explained: “A landing/touchdown velocity of about 2m/second is ideal and safe. And it is good that the tolerance will be for 3m/second, which means in case the best situation is not there, the lander will still do its job.”
More Fuel & New Sensor
The second change is the addition of more fuel to Vikram to handle more disruptions and have the “ability to come back” so there’s more cushion to handle the mission.
“Third, we have added a new sensor called the laser doppler velocity metre, which will look at the lunar terrain. And through laser source sounding, we will be able to get components of three velocity vectors. We will be able to add this to the other instruments available, thereby creating redundancy in measurement,” Somanath said.
Central Engine & Software
Isro has also improved the software to have more tolerance to failures like engine disruptions, thrust disruptions, sensor failures, etc, while also removing the central or fifth engine, which was added last minute during Chandrayaan-2.
“Five engines were OK with the earlier mass of the lander but now we’ve enhanced the mass by nearly 200kg. Also, given its weight now, we have to necessarily fire a minimum of two engines to do the landing, and cannot land with a single engine. Therefore, the central engine has been removed,” Somanath said.
Solar Panels & Antennas
He added that the space agency has extended solar panels and more panel area to generate power. Vikram will be able to generate power even if it lands in a different orientation and is not facing the Sun. It also has additional TTC (tracking, telemetry and command) antennas for redundancy.
But the major part of the preparations, he said, was dedicated to testing. “The whole of the last two years went for testing and not changes. The amount of tests we’ve done is much more than what was done during Chandrayaan-2. This is in terms of autonomous flights, helicopter flights, crane-mode landing simulation tests, drop tests, software simulation testbeds which were newly made to evaluate potential failures and recovery options etc,” he said.