Chandrayaan-3 Lunar Flyby: A Quiet Return With Big Scientific Lessons

Space missions rarely end when we think they do. Some of them have a gentle way of returning to the story, surprising us with new opportunities for science even after their prime mission is complete. Chandrayaan-3’s propulsion module did exactly that in November 2025, creating an unplanned but scientifically meaningful moment as it revisited the Moon’s neighborhood.

You must be thinking that Chandrayaan-3 Launched in 2023, and there was no orbiter then, what just happened in November 2025?

Well, let’s dig into…

What is the Propulsion Module?

The Chandrayaan-3 propulsion module (PM) is a remarkably resilient spacecraft. After delivering the Vikram lander and Pragyan rover to the Moon, it retained over 100 kg of fuel, enabling it to perform a Trans-Earth Injection maneuver and settle into a highly elliptical Earth orbit. Over the past two years, the PM has not only carried out lunar flybys, skimming within a few thousand kilometers of the Moon’s surface, but also continued its scientific mission using the SHAPE (Spectro‑Polarimetry of Habitable Planet Earth), which operates at 1 – 1.7 micrometers wavelengths. Looking ahead, its trajectory is expected to take it into a long-duration Earth orbit, during which it will keep gathering valuable spectroscopic data; eventually, depending on fuel and orbital dynamics, it may be deorbited or placed into a more stable graveyard orbit, serving as a model for future mission-end strategies in lunar and deep-space missions.

The propulsion module, originally designed only to ferry the lander and rover to lunar orbit, was placed in a large Earth-orbiting trajectory after finishing its main duties. For more than two years, it remained peacefully cruising around Earth, carrying the SHAPE instrument and offering occasional Earth-observation data.

Then, in early November 2025, its long, looping orbit brought it close enough for the Moon’s gravity to take over once again. This was not a planned maneuver; it was simply celestial mechanics at work.

Once inside the Moon’s gravitational sphere, the PM completed two elegant flybys:

• First flyby: around 3,700 km from the lunar surface, 6 November 2025 (07:23 UT)
• Second flyby: around 4,500 km, 11 November 2025 (23:18 UT)

ISRO’s tracking network monitored these passes carefully, not only for safety but also because such events are remarkably valuable for understanding orbital dynamics.

Was it a Controlled Maneuvering?

The short answer is NO, it was well educated maneuver.

No Thruster Firing Reported for the Flybys

• According to ISRO’s fly-by update, the module “entered the Moon Sphere of Influence (SOI)” on November 4, 2025, due to natural gravitational influence from Earth and the Moon. ISRO has explicitly stated: “overall satellite performance is normal … no close approach has been experienced with the other lunar orbiters.”

How do they manage the safety of other satellites?

• Collision Avoidance by Design (Earlier) / Planned Maneuvers: During the Earth-return phase (2023), ISRO designed the TEI (Trans-Earth Injection) trajectory with collision avoidance in mind: it explicitly considered avoiding a crash into the Moon and avoiding entering Earth’s GEO belt. ISRO raised the apolune (farthest point) in a planned maneuver on October 9, 2023, and performed TEI on October 13, 2023, to reach the intended long, safe Earth orbit. According to ISRO, the PM’s post-TEI orbit (1.8 lakh km × 3.8 lakh km) was chosen to minimize risk to active satellites and avoid uncontrolled reentry or debris generation. Their analysis tool (developed by the UR Rao Satellite Centre) factored in long-term disturbance torques, orbital dynamics, and close-approach risk.
• Trajectory Monitoring & Safety: The flyby events in November 2025 were “monitored very closely from ISRO Telemetry, Tracking and Command Network (ISTRAC).” ISRO noted no close approach to other lunar orbiters.

Why This Flyby Matters

Although the module didn’t carry dedicated lunar-science instruments, it still created meaningful scientific opportunities.

1. A Rare Natural Experiment

When a spacecraft re-enters the gravitational domain of a planetary body without active thrusting, engineers gain a naturally controlled test case for understanding:

• multi-body gravitational interactions
• perturbations on long-duration spacecraft
• orbit evolution under minimal energy input

These insights inform missions where fuel is precious and gravity assists are essential.

2. A New Orbital Geometry to Study

Because of the lunar encounter, the propulsion module’s orbit was reshaped significantly:

• Its trajectory expanded to nearly twice its earlier size
• Its inclination dropped from mid-latitudes to low inclinations
• Its orbital period changed dramatically

Such natural orbital transformations provide rich lessons for future Earth–Moon system navigation, including missions that may reuse hardware for extended phases.

3. Continued Value From Existing Hardware

Chandrayaan-3 has become a perfect example of how a mission can keep giving long beyond its intended life.
Even a propulsion module, considered “secondary hardware,” can contribute to:

• long-term spacecraft health studies
• telemetry and tracking experiments
• orbital evolution observations
• extended science via SHAPE when pointed toward Earth

It is a reminder that every part of a spacecraft can become a scientific instrument when its trajectory brings it to the right place at the right time.

What we learned and its future aspect?

Although the module didn’t collect surface data, its flybys still advanced lunar science by refining safe lunar orbits, informing collision-avoidance strategies, improving gravity-field models, and enriching Earth–Moon trajectory datasets, insights that will guide future low-energy transfers, extended missions, and spacecraft reuse for additional science.