What is “15 Minutes of Terror” in Chandrayaan-03 Mission?

What is the “15 Minutes of Terror”?

The critical technical manoeuvre that the Chandrayaan-3 lander will have to perform on August 23 when it enters the final 15 minutes of its attempt to make a soft landing on the Moon will be to transfer its high-speed horizontal position to a vertical one in order to facilitate a gentle descent on to the surface. The “15 Minutes of Terror” will be the most critical phase of the mission, but ISRO is confident that the Vikram lander will be able to complete these manoeuvres and land safely on the Moon’s south pole.

The initial preparation phase

The initial preparation phase comprises the final 1,139 seconds of the Chandrayaan-3 mission, and it is during this stage that the most critical operations will be performed.

The velocity reduction phase

The next phase, which is velocity reduction, will last 690 seconds, and thrusters will be fired to reduce Vikram’s velocity to one-fourth of its initial speed.

The fine braking phase

The final critical manoeuvre is the fine braking phase. During this phase, the lander will be aligned vertically and will hover at a height of 800 to 1,300 meters above the landing site. The lander will then use its thrusters to make small adjustments to its position in order to land safely.

The landing

Once the Vikram lander successfully lands on the lunar south pole, the sensors will signal the computer onboard the spacecraft. After this, the lander will be powered up completely, and Vikram will unfurl the rover ramp so that the Pragyan rover can embark on its lunar journey.

Learning from the failures

Before the Chandrayaan-2 probe could approach its final “terminal descent phase,”  it lost control and collided with the Moon’s surface during the “attitude hold phase” and the “fine braking phase”. The failure studies have been utilised to increase Chandrayaan-3’s touchdown probability. The initial rough braking phase of Chandrayaan-2 used a first-order automated guidance system; whereas Chandrayaan-3 is using a second-order guidance system. In Chandrayaan-3, the rough braking phase also uses an immediate thrust regulation.

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