PSLV-C61/EOS-09 Mission Failure: Technical Analysis & Impact | ISRO Launch Anomaly

1. Introduction

The Indian Space Research Organisation's (ISRO) Polar Satellite Launch Vehicle (PSLV) program has long been celebrated as a cornerstone of India's space endeavors, establishing a formidable reputation for reliability and versatility in deploying a wide array of satellites into diverse orbits. However, the launch of the PSLV-C61 mission on May 18, 2025, marked a rare and significant setback for this otherwise dependable system. The mission was tasked with carrying the strategically vital Earth Observation Satellite EOS-09, also known as RISAT-1B, along with several co-passenger payloads, into a Sun-Synchronous Polar Orbit (SSPO). Unfortunately, the mission was not accomplished due to a critical anomaly encountered in the third stage of the launch vehicle during its ascent.

The PSLV's high overall success rate, reportedly exceeding 95%, makes any failure a noteworthy event demanding thorough investigation. The PSLV-C61 incident represents only the third such failure in the vehicle's extensive flight history since its maiden launch in 1993. This rarity, compounded by the strategic importance of its primary payload, EOS-09, immediately elevates the significance of this event beyond a mere statistical blemish. It prompts a deeper examination into the potential factors that could lead to a deviation from the PSLV's established record of dependability.

This report aims to provide a comprehensive technical analysis of the PSLV-C61 mission failure. It will meticulously detail the mission's objectives, the characteristics of the launch vehicle and its payloads, the sequence of events that transpired during the launch leading to the anomaly, preliminary findings regarding the cause, ISRO's official response and investigative process, and the broader implications of this unsuccessful mission for India's space program and its strategic interests. The scope of this analysis will encompass not only the immediate technical aspects of the failure but also its context within ISRO's operational history and its potential repercussions.

2. PSLV-C61 Mission Profile and Objectives

The Polar Satellite Launch Vehicle (PSLV)

The Polar Satellite Launch Vehicle (PSLV) stands as ISRO's flagship launch system, renowned for its adaptability in delivering satellites to a multitude of orbits, including Sun-Synchronous, Low Earth, Geosynchronous Transfer, and navigation orbits. Developed indigenously, the PSLV has been instrumental in launching numerous Indian remote sensing, communication, and scientific satellites, as well as a significant number of international customer payloads, earning it the moniker of ISRO's "workhorse".

The PSLV-C61 mission utilized the PSLV-XL configuration, marking the 63rd flight of the PSLV program overall and the 27th flight employing this specific, more powerful variant. The PSLV-XL is distinguished by its use of six extended strap-on boosters (PSOM-XL), each carrying 12 tonnes of solid propellant, compared to the 9 tonnes in the standard PSLV's strap-ons. This enhancement provides greater thrust during the initial phase of flight, enabling the launch of heavier payloads. The vehicle is a four-stage launcher, employing alternating solid and liquid propulsion systems:

• First Stage (PS1): A large solid rocket motor, augmented by the six PSOM-XL strap-on boosters.
• Second Stage (PS2): An Earth-storable liquid propellant engine, known as the Vikas engine.
• Third Stage (PS3): A solid rocket motor designed for high thrust during the atmospheric and early exo-atmospheric phases of flight.
• Fourth Stage (PS4): Comprises two Earth-storable liquid propellant engines, providing the final thrust for precise orbital injection and maneuvering.

The PSLV-C61 vehicle stood at a height of 44.5 meters and had a lift-off mass of approximately 321 tonnes. The selection of the PSLV-XL variant for this mission directly reflected the substantial mass of its primary payload, EOS-09, which had a launch mass of nearly 1700 kg. This underscores that the PSLV-C61 mission was a significant undertaking, demanding considerable lift capacity, thereby amplifying the impact of its failure.

Overall Mission Objectives

The PSLV-C61/EOS-09 mission was ISRO's 101st launch from the Satish Dhawan Space Centre (SDSC) SHAR, Sriharikota. The primary objective of the mission was the precise deployment of the Earth Observation Satellite EOS-09 (also designated RISAT-1B) into a Sun-Synchronous Polar Orbit (SSPO). The targeted orbit was at an altitude of approximately 529 km with an inclination of 97.6° relative to the Earth's equator. Achieving this specific orbit is crucial for Earth observation satellites like EOS-09, as it ensures consistent lighting conditions for imaging and regular revisits over specific areas of interest.

Beyond the primary payload, a secondary objective was the launch of several co-passenger satellites for various Indian and international entities, demonstrating the PSLV's continued capability as a rideshare launch provider.

Furthermore, the mission profile included planned post-deployment operations for the PSLV's fourth stage (PS4). These operations involved the use of Orbit Change Thrusters (OCT) to lower the altitude of the spent PS4 stage, followed by its passivation. This procedure is designed to limit the orbital lifetime of the stage, thereby reducing the risk of space debris.⁴ Although these maneuvers were not executed due to the mission's premature failure, their inclusion in the plan highlights ISRO's ongoing commitment to responsible space operations and sustainable practices in the increasingly congested orbital environment. The failure to reach this phase meant that these advanced sustainability measures were also unrealized opportunities for this particular mission.

The following table provides a summary of the key mission parameters:

Table 1: PSLV-C61 Mission Fact Sheet

3. Payload Manifest and Objectives

Primary Payload: EOS-09 (RISAT-1B)

The principal payload aboard the PSLV-C61 mission was the Earth Observation Satellite-09 (EOS-09), also identified by its earlier designation, Radar Imaging Satellite-1B (RISAT-1B). EOS-09 was engineered as the seventh satellite in ISRO's indigenous RISAT series, serving as a follow-on to the RISAT-1 satellite (launched in 2012) and EOS-04 (RISAT-1A, launched in 2022).

Primary Objective and Strategic Importance:

The overarching objective of EOS-09 was to provide continuous, reliable, all-weather, and day-and-night Earth imaging capabilities. This capability is paramount for a wide spectrum of applications, ranging from strategic national security interests to various civilian and developmental programs. The satellite's launch was particularly significant given the prevailing geopolitical landscape and reported tensions along India's borders, underscoring its immediate strategic relevance.

Technical Specifications:

EOS-09 was equipped with a sophisticated C-band Synthetic Aperture Radar (SAR) as its primary instrument, operating at a frequency of 5.35 GHz. SAR technology is crucial because it can penetrate cloud cover, rain, fog, and darkness, conditions that render optical imaging satellites ineffective, thus ensuring uninterrupted surveillance and data acquisition.

Key technical features of EOS-09, based on available information and its lineage from RISAT-1/EOS-04, include:

• Imaging Modes: The satellite was designed with multiple imaging modes (five are mentioned in several sources) to cater to diverse observational requirements. These modes likely included variants of Spotlight (for high-resolution imaging of small areas), Stripmap (for continuous imaging along a strip), and ScanSAR (for wide-swath coverage at medium to coarse resolution). It was also expected to support co-polarization, cross-polarization, and potentially hybrid polarimetry, enhancing its ability to classify terrain, vegetation, and man-made structures.
• Resolution: EOS-09 was capable of achieving a spatial resolution of up to 1 meter in its high-resolution modes. Depending on the operational mode, resolutions could vary, potentially from 1 meter to around 50 meters, similar to its predecessors.
• Swath: The satellite offered a wide swath coverage, ranging from approximately 10 km in high-resolution modes to over 225 km in wide-scan modes.
• Launch Mass: ISRO's official mission page states the launch mass of EOS-09 as 1696.24 kg. Some other sources cite a slightly different figure of 1710 kg.
• Power: The satellite's solar arrays were designed to generate approximately 2200 W (2.2 kW) of power.
• Mission Life: EOS-09 had a planned operational mission life of 5 years.⁴
• Data Downlink: Payload data was to be transmitted to ground stations via X-band communication links.

Applications:

The dual-use nature of EOS-09 made it a critical asset:

• Strategic/Defence: The satellite was intended to significantly bolster India's national security by providing enhanced surveillance capabilities along its extensive land borders and coastlines. This included monitoring military activities, detecting infiltrations, supporting anti-terror operations, and enhancing maritime domain awareness. The RISAT series has a documented history of contributing vital imagery for national security purposes, including support for the 2016 surgical strikes and the 2019 Balakot air operations.
• Civilian: EOS-09 was also poised to contribute substantially to a variety of civilian applications. These included disaster management (providing critical data for flood mapping, cyclone tracking, landslide monitoring, and post-disaster damage assessment), agriculture (crop acreage estimation, soil moisture assessment, and crop health monitoring), forestry (deforestation monitoring and forest resource management), hydrology, urban planning, land-use and land-cover mapping, geological surveys, sea ice monitoring, and general object identification.

The loss of EOS-09 thus represents a considerable setback, creating a void in India's indigenous strategic surveillance capabilities and delaying the acquisition of crucial data for a multitude of civilian applications. This could potentially impede advancements in disaster response protocols, agricultural planning, and environmental monitoring efforts that were reliant on the high-resolution, all-weather data EOS-09 was designed to provide. The timeline for developing and launching a replacement for such a sophisticated satellite could extend over several years.

The following table summarizes the key specifications of the EOS-09 satellite:

Table 2: EOS-09 (RISAT-1B) Key Specifications

Co-Passenger Payloads

In addition to the primary payload EOS-09, the PSLV-C61 mission carried four co-passenger satellites:

• India CGUSAT: This was listed as an Indian payload. However, specific details regarding its full form (e.g., the expansion of "CGU"), purpose, or operating entity were not available in the provided information. While there are reports of India planning to launch numerous surveillance satellites, a direct link to CGUSAT is not established.
• India LEAP-1: Another Indian payload, LEAP-1 is associated with Dhruva Space's "Launching Expeditions for Aspiring Payloads" program. This mission reportedly involved Dhruva Space's P-30 nanosatellite platform and was intended to validate an imagery payload for an Australian customer. There appears to be a discrepancy in some records, with one source suggesting LEAP-1 was scheduled for an earlier PSLV flight (PSLV-C59). However, its inclusion in the official PSLV-C61 manifest indicates it was indeed part of this launch.
• Nepal MUNAL: This was a 1U CubeSat developed by the Nepal Academy of Science and Technology (NAST), with significant involvement from Nepali students. MUNAL was Nepal's second CubeSat. Its objectives were multifaceted, including the in-house design and development of the satellite, demonstration of a novel System-on-Chip (SSoC) based communication/on-board computer, continuation of missions from Nepal's first satellite (NepaliSat-1) such as Store & Forward communication and imaging, creation of a vegetation density database of Earth's surface, implementation of AI-based image segmentation for landmass identification, and collection of radiation data in Low Earth Orbit (LEO).
• United States Phoenix: This payload was listed as originating from the United States. Similar to CGUSAT, further specific details about the Phoenix satellite's nature, objectives, or the American entity responsible for it were not provided in the available documentation.

The inclusion of these international co-passenger payloads, despite the mission's ultimate failure, underscores the PSLV's established role as a commercial launch vehicle for international customers. However, any launch failure, particularly of a historically reliable vehicle like the PSLV, can have repercussions for international confidence and the commercial aspects of a space program, even if the impact is mitigated by a strong overall track record. The loss of these satellites represents a setback for their respective owners and a mission unfulfilled by ISRO's launch services.

4. The PSLV-C61 Launch and In-Flight Anomaly

Launch Details

The PSLV-C61/EOS-09 mission commenced its flight on Sunday, May 18, 2025. The launch occurred precisely at the scheduled time of 05:59 AM Indian Standard Time (IST), which corresponds to 00:29 Coordinated Universal Time (UTC). The launch took place from the First Launch Pad (FLP) at the Satish Dhawan Space Centre (SDSC) SHAR, located in Sriharikota, Andhra Pradesh, on India's eastern coast. This facility is ISRO's primary spaceport for launching satellite missions.

Initial Flight Sequence

According to initial reports and statements from ISRO, the lift-off of the PSLV-C61 was "textbook". The early phases of the flight proceeded nominally. The performance of the first stage (PS1), which includes the core solid rocket motor and the six extended strap-on boosters (PSOM-XL), was normal. This stage provides the initial massive thrust required to lift the 321-tonne vehicle off the launch pad and through the dense lower atmosphere.

Following the burnout and separation of the first stage and its strap-ons, the second stage (PS2), powered by the liquid-fueled Vikas engine, ignited as planned. The performance of this stage was also reported to be normal. The successful operation of these initial two stages indicated that the launch was proceeding according to the mission profile up to that point, setting the stage for the subsequent, critical upper-stage burns.

The Third Stage (PS3) Failure

The mission encountered a catastrophic anomaly during the operational phase of the PSLV's third stage (PS3). This stage is a solid rocket motor, identified as S7 in PSLV nomenclature, carrying approximately 7,650 kg of composite solid propellant. It is designed to provide a high-thrust impulse after the vehicle has passed through the denser parts of the atmosphere, significantly contributing to the velocity required for orbital insertion.

The anomaly occurred approximately six minutes into the flight, shortly after the ignition of the PS3 motor. Initial reports confirmed that the third stage motor ignited as expected. However, during its burn phase, a critical issue arose. ISRO Chairman V. Narayanan officially stated that "during the third stage there was a fall in the chamber pressure of the motor case". This "observation in the third stage," as it was also termed, was the direct cause of the mission failure.

The consequences of this pressure drop were immediate and severe:

• Deviation from Trajectory: The launch vehicle began to veer off its intended flight path. Visual data from the Mission Control Centre at SDSC SHAR reportedly confirmed this deviation.
• Loss of Velocity: Telemetry data indicated a drastic reduction in the vehicle's velocity. According to analysis by former ISRO scientist Manish Purohit, the velocity fell sharply from an expected value of around 6 km/s down to approximately 2.45 km/s during the third stage operation. Such a significant loss of velocity points to a near-complete failure of the third stage to deliver the required thrust.
• Mission Failure: Due to the third stage malfunction, the PSLV-C61 vehicle was unable to achieve the necessary altitude and velocity to place the EOS-09 satellite and its co-passenger payloads into the designated Sun-Synchronous Polar Orbit. The mission was subsequently declared "not accomplished," and all payloads were lost.

The failure occurring in the third stage, a solid rocket motor, distinguishes it from the recent GSLV NVS-02 mission failure in January 2025, which was attributed to a pyro valve malfunction in a liquid propulsion stage. While this suggests distinct immediate technical causes, the proximity of these two failures involving strategically important payloads has raised concerns and underscores the imperative for a thorough investigation by ISRO to identify any potential underlying systemic issues in quality control or integration processes.

The substantial drop in velocity from an anticipated 6 km/s to 2.45 km/s is a critical indicator of the severity of the third-stage malfunction. Orbital velocity for a Low Earth Orbit, such as the one targeted for EOS-09 at approximately 529 km altitude, is typically in the range of 7.6 to 7.8 km/s. The third stage is responsible for imparting a significant portion of this velocity. A reduction to 2.45 km/s at that point in the trajectory represents a massive velocity deficit that the fourth stage (PS4), with its limited propellant loading (1,600 kg), would be incapable of compensating for. The PS4 is designed primarily for final orbital trim and precise insertion, not for making up such a substantial performance shortfall from a preceding stage.

The following table provides a reconstructed timeline of the critical events during the PSLV-C61 launch, focusing on the third-stage anomaly:

Table 3: Timeline of PSLV-C61 Third Stage Anomaly (Approximate)

(Note: Specific timings for stage separations are based on typical PSLV flight profiles and may vary slightly for the C61 mission. The T+~6 minutes mark for the anomaly is based on reported information.)

5. Analysis of the Mission Failure

ISRO's Official Statements

Immediately following the unsuccessful launch, the Indian Space Research Organisation (ISRO) provided initial statements acknowledging the mission failure. ISRO Chairman V. Narayanan addressed the situation, stating, "During the third stage there was a fall in the chamber pressure of the motor case, and the mission could not be accomplished". He further elaborated that while the first two stages of the PSLV-C61 performed nominally and the third stage motor ignited as expected, an "observation" during the third stage's operation prevented the mission from achieving its objectives.

ISRO also communicated the status of the mission through its official social media channels. A post on X (formerly Twitter) stated: "Today 101st launch was attempted, PSLV-C61 performance was normal till 2nd stage. Due to an observation in 3rd stage, the mission could not be accomplished". These official communications consistently pointed to an issue with the third stage as the locus of the failure.

ISRO assured that a detailed technical analysis of the entire flight performance would be undertaken to determine the precise cause of the anomaly. This review is standard procedure for the organization in the event of any launch mishap.

Preliminary Technical Assessment: Focus on Third Stage (PS3) Solid Rocket Motor

The third stage of the PSLV, designated PS3, is a robust solid rocket motor utilizing Hydroxyl-terminated polybutadiene (HTPB) based composite propellant. Solid rocket motors are generally known for their reliability and simplicity compared to liquid-propellant engines. However, they are not immune to failure modes. A significant drop in chamber pressure, as reported for PSLV-C61, in a solid rocket motor can be indicative of several critical malfunctions:

• Breach in Motor Casing Integrity: A structural failure or burn-through of the motor casing would lead to a rapid depressurization and loss of thrust. This could be due to material defects, manufacturing flaws, or excessive thermal loads.
• Nozzle Failure: The nozzle is a critical component that accelerates the combustion gases to produce thrust. Issues such as severe throat erosion beyond design limits, ejection of nozzle components, or a structural failure of the nozzle assembly itself can result in a catastrophic drop in chamber pressure and thrust.
• Propellant Grain Anomalies: The solid propellant grain, which is the fuel/oxidizer mixture, must burn in a controlled and predictable manner. Anomalies such as cracks, voids, or debonding between the propellant and the motor casing can lead to an uncontrolled increase in the burning surface area, potentially causing overpressure and subsequent motor rupture, or conversely, an uneven burn that could lead to thrust termination or pressure drop if significant portions of the grain fail to combust properly or if combustion instability occurs.
• Ignition System Malfunction (Sustained Combustion Issues): While initial ignition of the PS3 motor was reported as normal, a problem with the ignition system that affects sustained combustion or an issue with the propellant's burning characteristics could also manifest as a pressure drop.

The reported rapid and substantial loss of vehicle velocity, from an expected 6 km/s down to 2.45 km/s, strongly suggests a catastrophic and near-total failure of the PS3 stage to produce thrust, rather than a mere underperformance or partial burn. This points towards a failure mode that led to a rapid cessation of the motor's operation.

Potential Causal Factors (as suggested by experts/retired officials)

In the aftermath of the launch failure, some preliminary expert opinions emerged. A retired senior ISRO official suggested that the PSLV-C61 third stage problem might have originated from a "faulty valve or electrical connector," which could have led to the observed drop in chamber pressure. While solid rocket motors do not typically employ valves for propellant flow control during their burn phase in the same way liquid engines do, this comment could potentially refer to pyro-activated devices used for ignition or stage separation, or perhaps an issue related to the nozzle's thrust vector control (TVC) system, which uses a flex nozzle actuated by electro-mechanical systems. An electrical connector malfunction is a plausible scenario, as it could affect the ignition sequence, the TVC system, or telemetry sensors monitoring stage performance.

The same retired official also voiced a broader concern, stating, "There's too much coincidence in back-to-back failures of missions critical to national security". This remark alludes to the GSLV-F15/NVS-02 navigation satellite mission failure in January 2025 and suggests a need to investigate potential systemic issues beyond isolated technical glitches. If an electrical connector issue were indeed a contributing factor to the PSLV-C61 failure, it might resonate with suspicions of electrical problems (such as a disconnected power line to a pyro valve) in the GSLV NVS-02 failure. Such a parallel, if established by the Failure Analysis Committee (FAC), could indicate a more systemic vulnerability in electrical integration, testing, or quality assurance processes across different launch vehicle programs, despite the differences in the specific stages and propulsion technologies involved. This possibility elevates the importance of the FAC's investigation to look for common root causes that might link these seemingly distinct failures.

Historical Context of PSLV and Other ISRO Failures

The PSLV has an impressive track record, with the C61 mission being its 63rd flight. Prior to this, the PSLV had experienced only two outright failures:

• PSLV-D1 (September 20, 1993): This was the first developmental flight of the PSLV. The mission failed due to a software error in the guidance and control system. The onboard software incorrectly implemented a corrective maneuver, leading to excessive pitch and ultimately causing the vehicle to deviate from its trajectory and crash into the Bay of Bengal. The IRS-1E satellite was lost.
• PSLV-C39 (August 31, 2017): This mission aimed to launch the IRNSS-1H navigation satellite. The launch failed because the payload fairing (heat shield), which protects the satellite during atmospheric ascent, did not separate as planned. Consequently, the satellite remained trapped within the fairing, attached to the fourth stage, and could not be deployed into its intended orbit. ISRO later attributed this failure to a malfunction in the pyro-activated separation system of the heat shield.

The PSLV-C61 failure is, therefore, the third unsuccessful mission in the PSLV's 32-year operational history. It is important to note that the nature of these three PSLV failures is distinct: PSLV-D1 was a software/guidance issue, PSLV-C39 was a mechanical/pyrotechnic system failure related to the payload fairing, and PSLV-C61 was a propulsion system failure in the third stage solid motor. This diversity in failure modes, even within a mature and reliable launch system, underscores the complexity of space launch operations and the continuous need for rigorous attention to all subsystems.

Comparing the PSLV-C61 failure to other recent ISRO mission failures provides additional context:

• GSLV-F10/EOS-03 (August 12, 2021): This mission failed due to a technical anomaly in the Cryogenic Upper Stage (CUS) of the GSLV Mk II. The failure was attributed to an inability to ignite the CUS engine due to a lower-than-expected pressure in the liquid hydrogen (LH2) propellant tank during the CUS ignition sequence.
• GSLV-F15/NVS-02 (January 29, 2025): This mission, carrying the NVS-02 navigation satellite (intended to replace the aging IRNSS-1E), failed to reach its orbit. The failure was attributed to a pyro valve malfunction in the liquid-fueled second stage (GS2). This valve reportedly failed to open, preventing the flow of oxidizer to the engines, despite the fuel pumps functioning correctly. The estimated financial loss for this mission was ₹300 crore.

ISRO has also encountered other hardware-related concerns with the PSLV in the past, such as a delay in the 2010 launch of IRNSS-1A due to a faulty actuator in the second stage, and an instance where a fully assembled PSLV had to be dismantled to replace a faulty gas motor in one of its systems.⁶ These historical instances, while not all leading to mission failures, highlight the ongoing challenges in maintaining the intricate systems of a launch vehicle.

The following table provides a comparative overview of these key ISRO launch failures:

Table 4: Comparative Overview of Key ISRO Launch Failures (PSLV & Recent GSLV)

6. ISRO's Investigative Process: The Failure Analysis Committee (FAC)

Establishment and Mandate of the FAC

Following any significant anomaly or mission failure, ISRO adheres to a well-established protocol which involves the immediate constitution of a Failure Analysis Committee (FAC). This was promptly initiated after the PSLV-C61 mission did not achieve its objectives. The FAC typically comprises a multidisciplinary team of senior scientists, engineers, and mission specialists drawn from various ISRO centers, possessing expertise relevant to the different subsystems of the launch vehicle and satellite. In some instances, an external government-appointed review body may also be involved to provide an independent oversight perspective.

The primary mandate of the FAC is to conduct a thorough, impartial, and data-driven investigation to meticulously identify the root cause or causes of the mission failure. Beyond pinpointing the technical fault, the FAC is also tasked with formulating comprehensive recommendations for corrective actions. These recommendations aim to prevent a recurrence of similar failures in future missions and to enhance the overall reliability of ISRO's launch systems.

Standard Investigation Procedures

The FAC undertakes a systematic and rigorous investigative process, which typically includes the following key steps:

• Telemetry Data Review: A comprehensive and minute-by-minute analysis of all available telemetry data transmitted from the launch vehicle during its flight is conducted. This includes scrutinizing parameters such as chamber pressures, temperatures, vehicle velocity and altitude, trajectory deviations, performance of propulsion systems, guidance and control system inputs and outputs, and data from various onboard sensors. For PSLV-C61, particular attention would be paid to the data from the third stage leading up to and during the observed pressure drop and velocity loss.
• Hardware and Test Record Examination: The committee reviews all ground test records and pre-flight preparation data for the specific stage and components that malfunctioned – in this case, the PS3 solid rocket motor. This includes examining manufacturing records, quality control checks, and results from any component-level or stage-level testing. If any hardware is recovered, it undergoes detailed forensic examination.
• Simulations and Reconstructions: Sophisticated computer simulations are often employed to replicate the flight conditions and the observed anomaly, helping to validate hypotheses about the failure sequence. The team also reconstructs the precise sequence of events by cross-referencing flight data with inputs from ground-based tracking systems and radar data.
• System Audits: The FAC may audit the design, manufacturing processes, assembly procedures, and quality assurance protocols related to the failed subsystem. This includes reviewing software algorithms for guidance and control, the structural integrity of components, and the performance of propulsion elements like the flex nozzle under simulated load conditions.
• Review of Launch Operations: The investigation also encompasses a review of all activities from the stage preparation at the launch complex, through the countdown procedures, to the moment of lift-off, to ensure no operational errors contributed to the failure.

ISRO's established FAC process is a critical mechanism for maintaining institutional learning, accountability, and public trust. The transparency demonstrated by typically releasing summaries of findings and corrective actions is vital for a national space agency, particularly when dealing with high-value, strategic missions. This approach ensures that each failure, however unfortunate, contributes to the long-term robustness and reliability of India's space program.

Expected Timeline and Reporting

The Failure Analysis Committee for the PSLV-C61 mission is expected to complete its investigation and submit a final report relatively quickly. Typically, such investigations take a few weeks to a month to deliver a comprehensive assessment. For the PSLV-C61, it has been indicated that the FAC report is anticipated within approximately one month of the incident.

The FAC's report will detail the identified root cause(s) of the failure, which could range from a specific component malfunction (e.g., material defect in the motor casing, nozzle burn-through, propellant grain anomaly) to issues in design, manufacturing, assembly, or pre-flight testing procedures. Based on these findings, the committee will propose a set of concrete recommendations for corrective actions.

Following the submission of the FAC report, ISRO is expected to implement these recommendations rigorously. This may involve redesigning specific faulty systems or components, upgrading safety checks and quality control measures, and revising operational procedures for future missions. Consistent with its past practices, ISRO is likely to release a public summary of the FAC's key findings and the corrective measures that will be undertaken, thereby ensuring transparency and demonstrating its commitment to learning from the setback.

The investigation for PSLV-C61 will likely face heightened scrutiny due to the "coincidence" of this failure with the GSLV NVS-02 incident earlier in the year, both involving strategically important national assets. Consequently, the FAC will be under considerable pressure not only to pinpoint the specific technical cause for the PSLV-C61 third-stage malfunction but also to thoroughly assess whether any shared systemic weaknesses – for instance, in overarching quality assurance frameworks, vendor management practices, or pre-flight testing protocols for critical systems – might have contributed to this recent spate of critical mission failures. The comprehensive scope of investigation indicated by former ISRO scientists, including examining elements like the "flex nozzle under similar load conditions" and auditing "guidance software, propulsion systems, and structural integrity", suggests that the FAC will indeed undertake a wide-ranging and deep dive to unearth all contributing factors.

7. Implications and Ramifications of the PSLV-C61 Failure

The unsuccessful launch of the PSLV-C61 mission carries significant implications across multiple domains, ranging from immediate operational impacts to broader strategic and financial consequences.

Impact on Earth Observation and Strategic Surveillance Capabilities

The primary loss from the PSLV-C61 failure is the EOS-09 satellite itself. This advanced C-band Synthetic Aperture Radar (SAR) satellite was designed to provide critical all-weather, day-and-night imaging capabilities. Its failure to reach orbit creates a temporary but significant gap in India's indigenous remote sensing infrastructure, particularly for high-resolution SAR data.

For national security, EOS-09 was intended to be a key asset for enhanced border surveillance, monitoring of military activities in sensitive regions, and bolstering maritime domain awareness along India's extensive coastline. The loss of this satellite means a delay in augmenting these crucial strategic surveillance capabilities, at a time when such assets are of increasing importance given the regional and global geopolitical climate.

On the civilian front, EOS-09 was expected to provide vital data for disaster management (such as flood mapping, cyclone tracking, and landslide assessment), agricultural planning (crop monitoring and soil moisture estimation), forestry management, and urban development. The absence of this satellite will mean that these sectors will not benefit from its advanced capabilities as planned, potentially affecting the timeliness and efficacy of responses and planning in these areas. Developing and launching a replacement for a satellite of EOS-09's complexity and capability could take several years, further extending this capability gap.

Financial Loss

The PSLV-C61 mission failure represents a substantial financial loss. The total estimated cost of the mission, including the launch vehicle and the primary satellite, is approximately ₹850 crore (equivalent to Rs 8 billion or roughly USD 102 million). This figure can be broken down into an estimated ₹300 crore (USD 36 million) for the PSLV-XL rocket and approximately ₹550 crore (USD 66 million) for the EOS-09 satellite.

In addition to the loss of the primary Indian payload, the failure also resulted in the loss of the co-passenger satellites belonging to domestic and international customers (CGUSAT, LEAP-1, Nepal's MUNAL, and USA's Phoenix). While the individual values of these smaller satellites may not be as high as EOS-09, their loss represents a financial and operational setback for their respective owners and operators. This financial toll is not merely a sunk cost; it also represents an opportunity cost, as these resources could have been allocated to other research and development initiatives, infrastructure upgrades, or additional space missions. Furthermore, the eventual need to build and launch a replacement for EOS-09 will necessitate additional, unplanned expenditure, potentially diverting funds and resources from other projects in ISRO's ambitious future roadmap, which includes critical missions like the Gaganyaan human spaceflight program, the Aditya-L1 solar observatory, and the Chandrayaan lunar exploration missions.

National Security Concerns

The failure of the PSLV-C61/EOS-09 mission has amplified national security concerns, primarily because it marks the second consecutive loss of an ISRO mission carrying a payload of strategic importance within a short period. The earlier failure involved the GSLV-F15 mission in January 2025, which was unable to deploy the NVS-02 navigation satellite. Navigation and surveillance satellites are critical components of modern defence and intelligence infrastructure.

Experts and retired officials have voiced concerns about this pattern, highlighting the "coincidence" of back-to-back failures in missions crucial to national security. These successive setbacks represent not only direct financial losses but also missed opportunities to enhance critical national capabilities in space-based intelligence, surveillance, reconnaissance (ISR), and positioning, navigation, and timing (PNT) services. The compounded effect of losing both a key navigation asset (NVS-02) and a sophisticated surveillance satellite (EOS-09) in quick succession could be perceived externally as a temporary vulnerability in India's strategic space-based C4ISR (Command, Control, Communications, Computers, Intelligence, Surveillance, and Reconnaissance) architecture. This underscores the urgency for ISRO to demonstrate a swift and effective recovery and to ensure the robustness of future strategic missions.

Effect on ISRO's Reputation and Future Programs

While the Polar Satellite Launch Vehicle has an exceptionally strong overall success rate and is rightly regarded as ISRO's workhorse, any failure, particularly one following another recent critical mission loss, can potentially impact the organization's esteemed reputation. This could be a "minor dent" in the context of the highly competitive global market for launching small- and medium-sized satellites, where reliability is a key differentiator.

The PSLV-C61 failure will inevitably necessitate a period of intensive review, implementation of corrective actions identified by the FAC, and rigorous re-validation of systems and processes. This meticulous approach, while crucial for ensuring future success, could potentially influence the schedule of upcoming ISRO missions. There is an expectation that ISRO will "double down on validation tests" before proceeding with high-profile future endeavors such as Gaganyaan, Aditya-L1, and Chandrayaan-4. While ensuring reliability is paramount, such enhanced validation cycles could introduce unforeseen delays to these nationally significant projects as ISRO works to incorporate all lessons learned from the PSLV-C61 anomaly. The incident will undoubtedly lead to increased scrutiny of ISRO's internal processes, quality control mechanisms, and vendor management practices.

8. Conclusion and Outlook

The PSLV-C61 mission, intended to deploy the advanced Earth Observation Satellite EOS-09 and several co-passenger payloads into a Sun-Synchronous Polar Orbit, unfortunately concluded in failure on May 18, 2025. The mission was aborted due to a critical anomaly experienced in the launch vehicle's third stage, specifically identified as a significant drop in the chamber pressure of the solid rocket motor during its operational phase.

This event marks a rare deviation from the otherwise stellar performance history of the PSLV, which has served as ISRO's most reliable launch vehicle for over three decades, successfully executing a vast majority of its 63 flights. The failure is particularly poignant given the strategic importance of the EOS-09 satellite, which was designed to provide crucial all-weather, day-and-night imaging capabilities for both national security and diverse civilian applications.

In line with its established protocols, ISRO has promptly constituted a Failure Analysis Committee (FAC) to conduct an exhaustive investigation into the root cause of the PSLV-C61 malfunction. This committee, comprising domain experts, will meticulously analyze telemetry data, review hardware and software systems, and scrutinize all aspects of the mission preparation and execution. ISRO has a commendable history of learning from past setbacks, such as the PSLV-D1, GSLV-F02, and EOS-03 failures, using these experiences to implement systemic improvements in testing, quality control, and design validation. This rigorous approach is expected to be applied to the current investigation.

The failure of the PSLV-C6 mission has undeniable consequences. It represents a significant financial loss, estimated at ₹850 crore, and creates a temporary void in India's advanced Earth observation and strategic surveillance capabilities. Furthermore, occurring relatively soon after the GSLV/NVS-02 mission failure, it has understandably raised concerns regarding the reliability of launches involving strategically vital assets.

The path forward for ISRO involves a meticulous and transparent investigation by the FAC, followed by the diligent implementation of its recommendations. This will be crucial for restoring full confidence in the PSLV program and for ensuring the success of future missions, including highly anticipated national projects like the Gaganyaan human spaceflight program, the Aditya-L1 solar mission, and further lunar exploration endeavors under the Chandrayaan program. The Indian space community, while acknowledging the setback, remains optimistic about ISRO's inherent resilience and its proven ability to overcome technical challenges. The PSLV-C6 failure, though a significant disappointment, will inevitably serve as a catalyst for further refinement and strengthening of ISRO's launch capabilities, ultimately contributing to the long-term robustness and success of India's ambitious space program.