Chandrayaan-3 Update: Propulsion module holds 150 kg fuel, extending lifespan from months to years

Ahead of Isro's attempt to softly land Vikram (the lander) on August 23, there's some good news about Chandrayaan-3: The propulsion module, which was initially expected to last for three-six months, still has more than 150 kg of fuel left. This suggests it could remain operational for several years to come.

"It has too much fuel, way beyond our expectations. There's a lot of fuel left as everything was very nominal on the way to the Moon and there were no contingencies requiring corrections (for which fuel would have been expended). We're left with almost all the margin, that's around 150+kg," stated Isro chairman S Somanath to TOI.

The propulsion module was filled with 1,696.4 kg of fuel during the launch on July 14. It carried out essential tasks, including five manoeuvres while still on Earth and another five manoeuvres as it journeyed towards the Moon. These activities took place from July 15 to August 17.


Each of these manoeuvres would have used up a portion of the fuel. Though there isn't an exact breakdown of the fuel consumption for each operation, initial estimations from Chandrayaan-2's first two manoeuvres could provide some insights. This is relevant as the current mission's trajectory has been quite similar to the one undertaken in 2019.

SHAPE gets more time
The Chandrayaan-2 orbiter transported 1,697kg of propellant, slightly exceeding the amount in the Chandrayaan-3 propulsion module. During the execution of the five manoeuvres on Earth and the trans-lunar injection, the orbiter consumed over 657 kg of fuel. In comparison, the Chandrayaan-3 propulsion module is expected to have used a bit more fuel during this phase.

After reaching lunar orbit, the Chandrayaan-2 orbiter needed around 749 kg of fuel for the separation manoeuvre. Similarly, the Chandrayaan-3 propulsion module would likely have utilised a comparable amount or slightly more during this phase. Having over 150 kg of fuel left, the module could continue circling the Moon much longer than the initial design's projection of three to six months.

This means the instrument Spectro-polarimetry of Habitable Planetary Earth (SHAPE) gets more time to study Earth. On whether SHAPE had been turned on for operations, Somanath said that as of late Friday, it was yet to be confirmed.

About final De-boost
Chandrayaan-3 successfully underwent its second round of deboosting where the orbit of the lunar satellite's Lander Module (LM) was reduced, the Indian Space Research Organisation (ISRO) said. While this activity brings the satellite closer to the moon, it is set to undergo internal checks, the space agency said.

"The second and final deboosting (slowing down) operation has successfully reduced the LM orbit to 25 km x 134 km. The module would undergo internal checks and await the sun-rise at the designated landing site. The powered descent is expected to commence on August 23, 2023, around 1745 Hrs IST," ISRO said in a post on 'X' (formerly Twitter) on Sunday.

Inputs from TOI