Chandrayaan-3 update: Isro to slingshot spacecraft on path to moon

The event has been scheduled between 12:00 am and 1:00 am on August 1 by the Indian Space Research Organisation (ISRO)

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India’s third lunar mission, the Chandrayaan-3,  will go through the critical Trans Lunar Injection (TLI)  tonight, a manoeuvre in which the spacecraft will be slingshot towards the Moon.

This event has been scheduled between 12:00 am and 1:00 am on August 1 by the Indian Space Research Organisation (Isro). The TLI manoeuvre is expected to last between 28 to 31 minutes, during which the engines on the Propulsion Module of the spacecraft will roar to life to increase the velocity.  

The thrusters of the  Chandrayaan-3 will be fired when the spacecraft is at the closest point to Earth (perigee) and not when at the farthest point (apogee).

"The next firing, the TransLunar Injection (TLI) is planned for August 1, 2023, between 12 midnight and 1 am IST," said Isro.

What is TransLunar Injection?

TLI is a propulsion manoeuvre used to set a spacecraft in an orbit to reach the moon. It involves TLI burn-up, usually done by a chemical rocket engine, which increases the spacecraft's velocity. This changes its orbit from a circular low-Earth orbit to a highly eccentric orbit. The burn-up is timed to target the Moon with precision as it revolves around the Earth.

The timing of the burn-up is set in a way that the spacecraft approaches apogee as the moon approaches. The spacecraft will enter the Moon's sphere of influence, and perform a hyperbolic lunar swingby.

The preloaded commands for the manoeuvre will be enabled around five-six hours ahead of the time the thrusters are expected to fire. The thrusters will also add to the velocity of Chandrayaan-3 and assist the spacecraft change its orientation to start the journey towards the Moon. After the TLI manoeuvre, the Chandrayaan-3 will seek to complete its lunar transfer arc. The spacecraft is expected to reach the lunar orbit after completing several complex manoeuvres.

On 25 July, ISRO successfully performed the fifth orbit-raising manoeuvre (Earth-bound perigee firing) of the Chandrayaan-3 spacecraft from the Isro Telemetry, Tracking and Command Network (ISTRAC).

The Chandrayaan-3 was launched on July 14 from the Satish Dhawan Space Centre in Sriharikota. The total cost of the mission is Rs 615 crore.