Even closer: Chandrayaan-3 undergoes second lunar orbit reduction manoeuvre

ISRO chief said its lander would be able to make a soft-landing even if all the sensors and two of its engines do not work.

BySouth First Desk

Published Aug 09, 2023 | 4:32 PMUpdatedAug 09, 2023 | 4:32 PM

ISRO Chandrayaan 3

Chandrayaan-3 spacecraft moved closer to the Moon’s surface on Wednesday, 9 August, after it underwent another orbit reduction manoeuvre, ISRO said.

ISRO’s third lunar expedition in 15 years, Chandrayaan-3 embarked on its month-long journey towards the moon on 14 July, piggybacking on the agency’s latest heavy-lift launch vehicle LVM3-M4 — nicknamed “Fat Boy” — from the spaceport Sriharikota in Andhra Pradesh.

It entered into lunar orbit or the Moon’s orbit on 5 August.

Also read: Orbit reduction manoeuvre brings Chandrayaan-3 closer to moon

‘Orbit is reduced’

“Even closer to the moon’s surface. Chandrayaan-3’s orbit is reduced to 174 km x 1437 km following a manoeuvre performed today,” ISRO said in a tweet.

The next operation is scheduled for 14 August, between 11.30 am and 12.30 pm, ISRO said.

A similar orbit reduction manoeuvre was carried out by the ISRO on Sunday.

As the mission progresses, a series of manoeuvres are being conducted by ISRO to gradually reduce Chandrayaan-3’s orbit and position it over the lunar poles.

According to ISRO sources, there will be two more orbit reduction manoeuvres to bring the spacecraft closer to the Moon.

These manoeuvres will be performed on 14 and 16 August to reach a 100 km orbit, following which the landing module, comprising the lander and rover will break away from the propulsion module.

Also read: Chandrayaan-3 mission is in ‘normal health’, says ISRO

‘Deboost’ on 23 August

After this, the lander is expected to undergo a “deboost” (the process of slowing down) and make a soft landing on the south polar region of the Moon on 23 August.

Over five moves in the three weeks since the 14 July launch, ISRO had lifted the Chandrayaan-3 spacecraft into orbits farther and farther away from the Earth.

Then, on 1 August in a key manoeuvre — a slingshot move — the spacecraft was sent successfully towards the Moon from Earth’s orbit. Following this trans-lunar injection, the Chandrayaan-3 spacecraft escaped from orbiting the Earth and began following a path that would take it to the vicinity of the moon.

Chandrayaan-3 is a follow-on mission to Chandrayaan-2 to demonstrate end-to-end capability in safe landing and roving on the lunar surface. It consists of a lander and rover configuration.

It comprises an indigenous propulsion module, a lander module, and a rover with the objective of developing and demonstrating new technologies required for inter-planetary missions.

The propulsion module will carry the lander and rover configuration till the 100 km lunar orbit. The propulsion module has a Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload to study the spectral and polarimetric measurements of Earth from the lunar orbit.

Also read: Chandrayaan 3 receives ground support from foreign space agencie

‘Will defenitely make soft landing’

Vikram, the lander of India’s third lunar mission Chandrayaan-3, would be able to make a soft-landing on the Moon’s surface on 23 August even if all the sensors and two of its engines do not work, ISRO chairman S Somanath said on Tuesday.

The entire design of the lander Vikram’ has been made in a manner that makes sure that it would be able to handle failures, Somanath said during a talk on Chandrayaan-3: Bharat’s Pride Space Mission, hosted by the non-profit organisation Disha Bharat.

“If everything fails, if all the sensors fail, nothing works, still it (Vikram) will make a landing. That’s how it has been designed — provided that the propulsion system works well,” Somanath said.

“We have also made sure that if two of the engines (in Vikram) don’t work this time also, it will still be able to land,” the ISRO chairman said.

“So the whole design has been made to make sure that it (Vikram) should be able to handle many failures, provided the algorithms work properly,” he added.

The biggest challenge before the ISRO team, according to him, is to make a horizontal Vikram’ land vertically on the lunar surface.

Somanath said once the lander separates from the orbiter, it would move horizontally. Through a series of manoeuvres, it will be brought to a vertical stance in order to land safely on the Moon.

This exercise is crucial, as ISRO failed to get its lander to touchdown safely on the Moon’s surface during the Chandrayaan-2 mission, he said.

“The ability to transfer from horizontal to vertical direction is the trick we have to play here. Here only we had the problem last time,” Somanath pointed out.

The challenge is also to make sure that the fuel consumed is lesser, the distance calculations are correct and all the algorithms work properly, the ISRO chief said.

However, the ISRO team this time has made arrangements to ensure that Vikram makes an attempt to land property even if there are some variations in the calculations, Somanath explained.

Mission objectives

The mission objectives of Chandrayaan-3 are to demonstrate a safe and soft landing on the lunar surface, to demonstrate rover roving on the Moon, and to conduct in-situ scientific experiments.

The lander will have the capability to soft land at a specified lunar site and deploy the rover that will carry out in-situ chemical analysis of the Moon’s surface during the course of its mobility.

The lander and the rover have scientific payloads to carry out experiments on the lunar surface.

Through the Chandrayaan 3 mission, scientists are aiming at mastering the technology of soft landing on the surface of the moon.

A successful mission would mean India becomes only the fourth country to accomplish the challenge, after the US, the former Soviet Union, and China.

About 16 minutes after lift-off, Chandrayaan 3 was separated from the rocket and orbited Earth a few times in an elliptical cycle — 170 km at its closest and 36,500 km at its farthest — before moving towards the lunar orbit.

A jubilant ISRO Chairman S Somanath said from the Mission Control Centre (MCC) that the rocket had injected Chandrayaan 3 into a precise orbit.

(With PTI inputs)