The Fall of a Giant: Unpacking India's PSLV-C61 and the EOS-09 Satellite Mission Failure

Prologue: A Legacy of Precision

India’s space ambitions have always walked a fine line between restraint and resilience. The Indian Space Research Organisation (ISRO), a symbol of this balance, has over decades created a reputation for reliable and cost-effective space missions. Among its crown jewels stands the Polar Satellite Launch Vehicle (PSLV), a workhorse rocket that has launched more than 50 successful missions since the 1990s. Each mission stitched together India's growing capability to observe, analyze, and respond to the needs of its citizens and the global scientific community.

But on May 18, 2025, that streak took a severe blow.

The PSLV-C61 mission, tasked with deploying the advanced Earth Observation Satellite EOS-09, failed mid-flight. It was a rare misstep for a launcher often regarded as one of the most reliable in the world. This is the story of that failure — what happened, why it mattered, and what it means for the future of India’s space program.

Chapter 1: The Mission That Carried Many Hopes

The PSLV-C61 was not just another flight in the PSLV's timeline. It carried with it the weight of new surveillance ambitions, data mapping needs, and international prestige. Its payload, the EOS-09 satellite, was built to observe the Earth in ways few other Indian satellites could.

EOS-09, short for Earth Observation Satellite 09, was designed with Synthetic Aperture Radar (SAR) technology. SAR-equipped satellites have a unique advantage: they can capture images through clouds, at night, and during adverse weather conditions. For a country like India, which deals with frequent monsoons, cyclones, and a wide variety of terrain types, SAR data is essential.

The satellite was planned to serve several key functions:

• Disaster Monitoring: Real-time data for floods, landslides, and earthquakes.

• Agricultural Assessment: Tracking crop health and estimating yield in cloudy conditions.

• Border Surveillance: Day-and-night imaging for defense and intelligence purposes.

• Climate Monitoring: Observing glaciers, river systems, and forests.

Launching EOS-09 was to be a major step in improving India’s Earth observation capabilities — effectively giving the country eyes that could see through storm and darkness.

Chapter 2: The Rocket That Rarely Fails

The vehicle chosen to carry EOS-09 into space was PSLV, specifically the PSLV-C61 variant. The PSLV has four stages, alternating between solid and liquid propulsion:

1. First Stage (Solid Fuel): Provides the initial thrust to lift the rocket off the launch pad.

2. Second Stage (Liquid Fuel): Guides the rocket through the thickest part of Earth’s atmosphere.

3. Third Stage (Solid Fuel): Propels the vehicle further into space.

4. Fourth Stage (Liquid Fuel): Final maneuvering and satellite separation.

This configuration has made PSLV known for reliability. Since its inception in 1993, it has launched numerous national and international satellites, including India’s Mars Orbiter Mission (Mangalyaan) and Chandrayaan-1 to the Moon. The PSLV became a symbol of how India could “do more with less” — affordable space missions without compromising performance.

The PSLV-C61 launch was set to continue that legacy.

Chapter 3: The Countdown Begins

On the morning of May 18, 2025, the atmosphere at the Satish Dhawan Space Centre in Sriharikota was electric. Engineers, scientists, technicians, and guests watched as the PSLV-C61 stood on the launch pad, gleaming under the early sunlight.

The rocket’s systems had been checked and double-checked. The fuel tanks were full. Weather conditions were optimal. The countdown reached zero.

And with a thundering roar, PSLV-C61 lifted off from the Earth.

Chapter 4: A Mission Unraveled

For the first few minutes, everything went as expected.

• T+0 to T+110 seconds: The first stage ignited and performed flawlessly.

• T+110 to T+260 seconds: The second stage fired successfully, taking the vehicle beyond the densest layers of the atmosphere.

• T+260 seconds: The third stage ignited.

And then, a problem emerged.

Mission control noticed a drop in chamber pressure in the third stage. The solid fuel booster, which was supposed to push the rocket to orbital velocity, wasn’t providing the required thrust. Within seconds, it became clear: the vehicle wasn’t going to make it to its intended orbit.

The rocket did not explode. It did not veer wildly. It simply fell short — underpowered, off-course, and unable to fulfill its final objective.

The fourth stage never had the chance to kick in. The mission was aborted.

Chapter 5: In Search of the Cause

In a matter of hours, ISRO released a preliminary statement: a malfunction in the third stage had caused the failure. More specifically, a sudden drop in chamber pressure, likely due to fuel combustion irregularity or structural fault, had reduced the thrust needed for orbital insertion.

While a detailed Failure Analysis Committee was formed to look into the specifics, early theories included:

• Fuel Grain Cracking: In solid boosters, any imperfection in the fuel block could lead to uneven burning.

• Nozzle Failure: If the nozzle was damaged or improperly aligned, it could reduce exhaust velocity.

• Manufacturing Anomaly: A deviation during fabrication or quality control might have gone unnoticed.

Failures in solid stages are notoriously hard to predict and even harder to correct mid-flight. Unlike liquid stages, they cannot be throttled, shut down, or restarted.

Chapter 6: The Fallout

The loss of the EOS-09 satellite was a major setback for India’s remote sensing capabilities. It delayed the introduction of crucial infrastructure for national security and disaster management. But the consequences went deeper.

For ISRO:

• Credibility Dent: Even though PSLV’s track record remained among the best globally, this failure cast a shadow.

• Delayed Missions: Other payloads relying on similar configurations would now be pushed back for revalidation.

• Budget Reallocations: Resources would have to be diverted to investigation and recovery instead of development.

For the Public:

• Loss of Trust: While public support for ISRO is strong, any failure causes a stir in national discourse.

• Delay in Services: Meteorological predictions, agricultural mapping, and emergency response tools all would experience gaps in coverage.

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Chapter 7: Lessons in Failure

Yet, there’s something inherently scientific about failure — it teaches more than success often can.

Every space agency — from NASA to ESA to Roscosmos — has faced launch failures. What defines progress is how these failures are handled.

For ISRO, the C61 incident became an opportunity to:

• Improve Third Stage Design: More robust checks for structural integrity and fuel consistency.

• Reassess Manufacturing Processes: Automation and machine learning-driven quality inspection systems.

• Update Launch Protocols: Additional sensor layers to catch early warnings in flight.

Moreover, the incident re-emphasized the value of fail-safes and simulations. ISRO’s transparency in acknowledging the failure and establishing a formal review reflected institutional maturity — a vital trait for any world-class space agency.

Chapter 8: The Road to Redemption

Just days after the failed launch, teams at ISRO returned to their labs and workstations, already laying the groundwork for what would follow. The timeline for PSLV-C62 was re-evaluated. The SAR payload that was to be on EOS-09 was considered for a replacement satellite, possibly EOS-10.

At the same time, ISRO continued work on its other big projects:

• Gaganyaan: India’s first crewed mission to space.

• Chandrayaan-4: A return mission to study the Moon’s far side.

• Aditya-L1: A solar observatory mission set to orbit the Lagrange Point 1.

Failures don’t stop progress. They guide it.

Epilogue: A Glance into Tomorrow

The PSLV-C61 failure, though painful, is but a chapter in a much larger story. It reminds us that space exploration is not about guaranteed results — it's about risk, persistence, and vision. ISRO, by all measures, remains a vital player in the global space arena, and its ambitions have not dimmed.

What EOS-09 was meant to do will eventually be accomplished — perhaps even better, with a redesigned successor and a smarter launch system.

The stars are still out there, waiting.