Chandrayaan-3: India's ambitious Chandrayaan-3 mission entered its last round as Vikram lander was successfully separated from the Propulsion Module on Thursday (August 17). After the separation from the propulsion module, now Vikram will reach the lunar orbit with the lander rover. Both - propulsion module and lander - left each other's surface and Vikram headed towards the moon.
In the next step, Lander Module will descend to a slightly lower orbit around the Moon on Friday. After separation, the lander is expected to undergo a "deboost" (the process of slowing down) to place it in an orbit where the Perilune (closest point to the Moon) is 30 kilometres and Apolune (farthest point from the Moon) is 100 km. From this orbit, the soft landing on the south polar region of the Moon will be attempted on August 23, ISRO said.
"Thanks for the ride, mate! said the Lander Module (LM). LM is successfully separated from the Propulsion Module (PM). LM is set to descend to a slightly lower orbit upon a deboosting planned for tomorrow around 1600 Hrs., IST," ISRO said in a post on X (formerly Twitter).
"Meanwhile, the Propulsion Module continues its journey in the current orbit for months/years. The shape payload onboard it would - perform spectroscopic study of the Earth’s atmosphere and measure the variations in polarization from the clouds on Earth – to accumulate signatures of Exoplanets that would qualify for our habitability. This payload is shaped by UR Rao Satellite Centre/ISRO, Bengaluru," ISRO added.
Chandrayaan-3 completes last Moon-bound manoeuvre
With this, the spacecraft has completed all of its Moon-bound manoeuvres, now, ISRO is prepared for the separation of the lander module -- comprising the lander and rover -- from the propulsion module.
"Today’s successful firing, needed for a short duration, has put Chandrayaan-3 into an orbit of 153 km x 163 km, as intended. With this, the lunar bound manoeuvres are completed. It's time for preparations as the Propulsion Module and the Lander Module gear up for their separate journeys," ISRO said.
Following its launch on July 14, the Chandrayaan-3 spacecraft entered into lunar orbit on August 5, following which orbit reduction manoeuvres were carried out on August 6, 9 and 14. As the mission progressed, a series of manoeuvres were conducted by ISRO to gradually reduce Chandrayaan-3's orbit and position it over the lunar poles.
The space agency's chairman S Somanath recently said that the most critical part of the landing is the process of bringing down the velocity of the lander when it begins its descent from a height of 30 km to the final landing (position), and that the ability to transfer the spacecraft from horizontal to vertical direction is the "trick we have to play".
"The velocity at the starting of the landing process is almost 1.68 km per second, but this speed is horizontal to the surface of the moon. The Chandrayaan-3 here is tilted almost 90 degrees. It has to become vertical.
So, this whole process of turning from horizontal to vertical is a very interesting calculation mathematically. We have done a lot of simulations. It is here where we had the problem last time (Chandrayaan-2)," Somanath explained.
Further, it has to be ensured that fuel consumption is less, the distance calculation is correct, and all the algorithms are working properly, he added.
"Extensive simulations have been done, guidance designs have been changed, and a lot of algorithms have been put in place to make sure that in all these phases the required dispersions are handled...
to attempt to make a proper landing," he said.
Over five moves in the three weeks since the July 14 launch, ISRO lifted the Chandrayaan-3 spacecraft into orbits farther and farther away from Earth. Then, on August 1 in a key manoeuvre -- a slingshot move -- the spacecraft was sent successfully towards the Moon from Earth's orbit. Following this trans-lunar injection, Chandrayaan-3 escaped from orbiting the Earth and began following a path that would take it to the vicinity of the Moon, and eventually into Moon's orbit.
What is Chandrayaan-3 mission?
Chandrayaan-3 is a follow-on mission to Chandrayaan-2 (2019) to demonstrate end-to-end capability in safe landing and roving on the Moon's surface. It comprises an indigenous propulsion module, lander module, and a rover with an objective of developing and demonstrating new technologies required for inter-planetary missions. The propulsion module, other than carrying the lander and rover configuration till about 100 km lunar orbit, carries the Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload to study spectral and polarimetric measurements of the Earth from lunar orbit.
The mission objectives of Chandrayaan-3 are to demonstrate safe and soft landing on the lunar surface, to demonstrate the rover operating on the Moon, and to conduct in-situ scientific experiments.
Expressing happiness over Chandrayaan-3 mission going successfully so far, former ISRO Chairman K Sivan, who was heading the space agency during the second lunar mission, said the lander's touch down on August 23 "is a great moment we are looking forward to."
He said that Chandrayaan 2 also had gone through all these phases successfully, and during the landing's second phase, an "issue" came up, and the mission couldn't be achieved as intended.
"Now definitely more anxiety will be there on the landing manoeuvre. Last time it couldn’t be successful. This time everyone is waiting for the great moment. I’m sure it will be successful because we have understood the failures we had during Chandrayaan 2. We have corrected it and, in addition to that, wherever margins were less, extra margins are added. Wherever redundancy was not there, that also now has been provided.
This time we are expecting the mission will be successful. We are confident in that," he added.
