The Indian Space Research Organisation (ISRO) on Wednesday successfully performed the critical 'Trans Lunar Insertion' (TLI) manoeuvre of Chandrayaan-2 spacecraft at 2:21am, following which the spacecraft left the earth's orbit and has entered the Lunar Transfer Trajectory, heading towards the moon.
During this manoeuvre, the spacecraft's liquid engine was fired for about 1,203 seconds. The spacecraft’s orbit was progressively increased five times from July 23 to August 6. Chandrayaan-2 is expected to reach the moon's orbit on August 20 and the spacecraft's liquid engine will be fired again to insert the spacecraft into the lunar orbit. Following this, there will be further four orbit manoeuvres to make the spacecraft enter into its final orbit passing over the lunar poles at a distance of about 100 km from the moon’s surface.
As per experts, Wednesday's manoeuvre was one of the critical ones towards the spacecraft's journey to the south pole of the moon as it needed high accuracy. “Typically this requires very accurate simulation taking into account various complex factors like non-uniformity of the earth's and the moon's gravity; Moon's true orbital motion; gravitation from other astronomical bodies; effect of solar radiation pressure, etc,” Pawan Kumar Chandana, CEO of Hyderabad-based Skyroot Aerospace, told THE WEEK.
However, despite it being a critical manoeuvre, ISRO has enough expertise in performing such feats as it had done earlier with Chandrayaan-1. Hence, Wednesday's manoeuvre can be termed as a routine engagement for the ISRO team and was done with utmost accuracy demonstrating the prowess of the ISRO scientists.
“An unsuccessful TLI would have meant that the spacecraft would not have got the necessary velocity to reach the moon. That would have meant that a propulsion system error of the spacecraft. Had this manoeuvre not been successful, it would have been very challenging for the mission. But TLI is to be treated as a routine manoeuvre since ISRO has already experience with it and has done it successfully before,” remarked Narayan Prasad, co-founder and chief operations officer of Satsearch.
This will be another critical manoeuvre as the spacecraft approaches the moon's orbit. “Once the spacecraft is approaching the moon, the propulsion system has to fire at the right time to be able to be captured around the lunar orbit. If it doesn’t, then either the craft can crash onto the moon or completely miss the moon and wander into outer space,” explained Prasad.
The next set of manoeuvres is also expected to be performed without any difficulty as ISRO had done a similar and successful attempt during Chandrayaan-1.
Upon accomplishing the next manoeuvres, the Vikram lander will separate from the orbiter on September 2. Two orbit manoeuvres will be performed on the lander before the initiation of powered descent to make a soft landing on the lunar surface on September 7.