The orbiter on Chandrayaan-2, which ISRO initially said would go around the Moon for just one year, may now have a lifespan of at least two years. The orbiter was packed with 1,697 kg of propellant at launch, and it has expended about 130 kg for the two manoeuvres on July 24 and 26. As on Saturday, the orbiter had more than 1,500 kg of propellant

BANGALORE: The orbiter on Chandrayaan-2, which Indian Space Research Organisation (ISRO) initially said would go around Moon for one year, will be able to have a lifespan of at least two years if everything goes as per ISRO’s current estimations.

At least five people associated with the Rs 978-crore mission told TOI that it’s life may be extended by an additional year as per the current status of things, which is a significant bonus from the one-year lifespan that ISRO chairman K Sivan had said it would have on June 12.

“Chandrayaan-1 was planned for a longer life than it had but a problem with the power converters led to a curtailed lifespan, which has been corrected for Chandrayaan-2. And, going by the amount of fuel that will remain in the orbiter after all the manoeuvres, we will have Chandrayaan-2 orbiting for at least two years,” a source working with the mission team, said.

The orbiter was packed with 1,697 kg of propellant at the time of the launch, and it has already expended about 130 kg of it for the two manoeuvres ISRO conducted on July 24 and 26. As on Saturday (July 27), the orbiter had more than 1,500 kg of propellant remaining.

A scientist said that a better-than-textbook launch has given the agency an advantage of about 40-odd-kg of fuel. Besides, another scientist said: “Even as per the initial plan we had, additional fuel was budgeted keeping in mind some emergencies. But going by present estimates and calculations, we will have more fuel than it is needed to orbit for a year.”

Sivan had earlier said that all the manoeuvres until the separation of Vikram, the lander, will be fuelled by the propellants on the orbiter. This means that there are nine more manoeuvres before the separation, during which many more kilograms of fuel will be used up.

According to ISRO’s present estimation, at the end of all Earth-bound and lunar-bound manoeuvres, the orbiter should be left with at least 290.2 kg of fuel when it is in the 100kmX100km orbit around Moon (see graphic). 

“This will be more than enough for it to go around Moon for two years as there will be no more big manoeuvres required,” the first scientist said. Another scientist said that the only manoeuvres after reaching the desired lunar orbit, if at all, would be minor ones. 

“But, given that Moon’s gravity is not uniform unlike Earth, the orbiter needs to be kept in the correct orbit, which will require periodic intervention. If left unattended, the closest point to Moon could become very narrow. These manoeuvres will use up some fuel,” the scientist explained. 

All the scientists emphasised that they could only confirm the exact number of additional days the orbiter could have around Moon once the lunar craft is settled into an orbit there. “Chandrayaan-2 is expected to be inserted into the lunar orbit on August 20, and we can assess how long it would last once it is there and we know exactly how much fuel is left,” one of them said.