In a brilliantly executed sequence, ISRO successfully separated the Chandrayaan-3’s lander module, the Vikram, from the spacecraft’s propulsion module.
The separation took place on August 17 at around 1:30 PM. To commemorate this, the team handling Chandrayaan-3 took to X and posted –
Vikram’s deboosting phase
The Vikram Lander is about 30-100 kilometers from its intended landing position. Following the separation, the lander has entered its “deboost” phase.
The idea is that the Vikram lander will slowly start accelerating in a direction opposite the Moon’s gravitational pull so that the lander’s velocity gradually decreases as it approaches the lunar surface. Please think of this maneuver as slowly tapping the brakes of your car or bike to slow it down. ISRO will carry out the first significant deboosting tomorrow, at 4:00 PM
The Vikram lander is now at a junction where the closest point on the Moon, known as Peruline, will be 30 kilometers away, and its farthest point, the Apolune, will be about 100 kilometers from the Moon.
Following its separation from the lander module, Vikram-3 is scheduled to perform a soft landing on the south pole of the Moon on August 23. Following its landing, ISRO will soon get the Pragyan rover working its margin on the Moon.
Chandrayaan-3’s journey to the moon
After its launch on July 14, the Chandrayaan-3 spacecraft entered its lunar orbit on August 5. ISRO then performed a series of orbit reduction maneuvers to slowly trim Chandrayaan-3’s orbit and nudge the spacecraft into position above the Moon’s poles. In a choreographed sequence, these orbit-reducing maneuvers occurred on August 6, 9, 14, and 16.
Adding to the excitement, K Sivan, the former head of ISRO who led the Chandrayaan-2 mission, expressed his upbeat outlook. He expressed optimism regarding Chandrayaan-3’s anticipated landing on the Moon’s surface on August 23.
With an air of anticipation, Sivan highlighted the significance of this moment, stating that August 23 holds the promise of a remarkable achievement.
Zone of Terror: Been here before
K Sivan acknowledged that Chandrayaan-2 successfully sailed through similar phases yet encountered a challenge during the landing’s second phase in the terror zone.
The zone of terror or the terror zone is usually the very last leg of the landing of any space rocket. Multiple things can go wrong during this phase. For the Chandrayaan-2 and Chandrayaan-3, the last 15 minutes before the Vikram lander touches down is usually considered the zone of terror. Everything from this mark on is mission critical – the timing of activating and deactivating the boosters, the force the advocates exert, any variations in wind or fuel weight of the lander – all these things come into play.
Shedding light on the intricacies of the Chandrayaan-3 mission, ISRO’s current chief, S Somanath, provided insights into its design philosophy. He noted that, unlike its predecessor, Chandrayaan-3 is crafted with a failure-based design approach rather than one driven solely by success.
Somanath explained that the focus is on addressing potential deviations or faults. This strategy prioritizes understanding what could happen and formulating safeguards to counter those scenarios. “The ability to handle parameter variation or dispersion was very limited in Chandrayaan-2. So, instead of a success-based design, we are doing a failure-based design in Chandrayaan-3. What all can fail, and how to protect it — this is our approach,” Somanath told PTI.
