When Chandrayaan‑3 thundered off the launch pad at Sriharikota on 14 July 2023 at 2:35 PM, the nation’s eyes followed the LVM‑3 rocket carrying India’s lunar ambitions skywards. The mission had a clear and direct goal: to achieve a soft landing on the Moon, deploy a rover, and conduct experiments to study the lunar surface.

On 23 August 2023, India made history by becoming the fourth nation to achieve a soft landing on the Moon and the very first to touch down near the lunar south pole. The mission was widely hailed as a triumph of precision engineering and scientific excellence.

Yet, what followed has arguably been even more remarkable.

A New Chapter For The Propulsion Module

After the Vikram lander and Pragyan rover completed their designated tasks on the Moon’s surface, the propulsion module — the stage that had carried them to lunar orbit — remained circling the Moon silently at an altitude of about 150 kilometres. Its role, in theory, was over.

But rather than switch it off, ISRO’s mission engineers saw a chance to extend its utility. In October 2023, they executed a daring experiment: a Trans‑Earth Injection (TEI) manoeuvre. This manoeuvre, never planned initially, gave the propulsion module a controlled boost that sent it on a complex trajectory back toward Earth.

The idea was to study how a spacecraft behaves under dual gravitational influences — those of the Earth and the Moon — and to test orbital prediction models in real time.

The Science Behind The Surprising Orbit

Contrary to expectations, the module did not fall back directly to Earth. Instead, it entered an elongated, highly elliptical orbit, stretching out to several hundred thousand kilometres.

Girish Linganna, a noted space analyst, explained that when the spacecraft moves close to Earth on this path, it speeds up sharply due to the strong gravitational pull. As it travels outward, the Earth’s hold weakens, and the module drifts into regions where the Moon’s gravity becomes comparatively stronger.

At those great distances, the shift in gravitational dominance naturally draws the spacecraft back toward the Moon’s sphere of influence — the zone where the Moon’s gravity is greater than Earth’s.

“It’s like a game of celestial catch,” Linganna observed. “Earth and Moon take turns influencing the spacecraft’s path, altering its speed and direction in subtle but fascinating ways.”

Flybys And Orbital Transformations

On 4 November 2025, the propulsion module once again crossed into the Moon’s domain. Two days later, on 6 November, it completed its first unplanned lunar flyby, skimming 3,740 kilometres from the Moon’s surface. A second flyby occurred on 11 November at a distance of 4,537 kilometres.

The Indian Deep Space Network (IDSN) monitored these manoeuvres meticulously, gathering invaluable telemetry from millions of kilometres away.

Each flyby produced significant orbital changes. The module’s orbit expanded from 1 lakh by 3 lakh kilometres to an extraordinary 4.09 lakh by 7.27 lakh kilometres. Its inclination — the tilt relative to Earth’s equator — shifted from 34 degrees to 22 degrees. These adjustments, achieved purely through gravitational interactions, effectively turned passive motion into a live demonstration of natural orbital mechanics.

Learning Beyond The Mission’s Design

The primary achievement of this phase lies not in distance covered or precision of control, but in scientific learning.

By prolonging the mission with leftover propellant, ISRO engineers gained hands‑on experience in tracking deep‑space objects and refining prediction algorithms that incorporate complex, multi‑body gravitational influences. The data from this extended experiment will feed directly into future lunar, Martian, and interplanetary missions.

Equally valuable has been the opportunity to study disturbance torques — small, cumulative forces from solar radiation, thermal gradients, and gravitational asymmetries. These subtle effects can, over time, cause spacecraft drift. Understanding them more precisely allows engineers to design better control systems and predictive models for long‑duration missions.

Transforming Residual Assets Into Strategic Knowledge

Most space agencies have carried out flybys and gravity‑assist manoeuvres, but India’s approach was unique. It was achieved not with a dedicated spacecraft, but with an already‑successful mission component that still had a few kilograms of propellant left in its tanks.

Instead of leaving the module as inert lunar debris, ISRO transformed it into an active research platform — a testbed for deep‑space manoeuvres, precision tracking, and system endurance.

This not only demonstrates technical maturity but also a culture of innovation grounded in thrift — a hallmark of India’s space programme.

A Preview of Future Missions

The Chandrayaan‑3 propulsion module’s revived journey underscores how ingenuity can extract maximum value from existing assets. The lessons learned will inform orbital planning for missions such as Chandrayaan‑4 and the planned Lunar Gateway collaborations, as well as enhance India’s understanding of cislunar space — the vast region between Earth and the Moon now seen as the next frontier of strategic space activity.

Through this transformation, a completed mission was reborn as a scientific opportunity. ISRO has shown that even a spacecraft running on borrowed time can yield fresh discoveries, extending India’s footprint in lunar science and deep‑space engineering.

In essence, Chandrayaan‑3’s propulsion module continues to prove that in space exploration, creativity is as valuable as fuel — and that every orbit presents a new chance to learn.

Based On The Week Report