The failure of the PSLV-C61 mission on May 18, 2025, which resulted in the loss of the EOS-09 (RISAT-1B) satellite, has temporarily left India without a critical asset for all-weather Earth observation and surveillance.

EOS-09 was designed to provide high-resolution, real-time imaging using C-band Synthetic Aperture Radar (SAR), capable of monitoring the Earth’s surface day or night, regardless of weather conditions. This capability is vital for border security, disaster management, agricultural monitoring, and urban planning, especially given India’s extensive land borders and coastline.

Current Alternatives And Operational Satellites

Despite the setback, India retains a robust fleet of operational Earth observation satellites that can partially fill the gap left by EOS-09:

EOS-04 (RISAT-1A): The closest operational counterpart to EOS-09, EOS-04 uses similar C-band SAR technology for all-weather imaging. While it can handle many of the urgent surveillance and disaster response tasks, the absence of EOS-09 reduces the frequency and redundancy of observations, potentially impacting continuous data availability for critical applications.

RISAT-2B: Equipped with X-band SAR, RISAT-2B provides sharper images, making it valuable for military surveillance. However, its imaging is less suited for broader environmental monitoring tasks such as vegetation or water body assessment.

CARTOSAT Series: These satellites offer high-resolution optical imaging, ideal for mapping and urban planning. Their limitation is reduced effectiveness during cloudy or night time conditions, as they lack SAR’s all-weather capability.

RESOURCESAT: Focused on resource management and environmental monitoring, RESOURCESAT satellites contribute valuable data, though they do not match the all-weather, high-frequency imaging of EOS-09.

What EOS-09 Was Replacing

EOS-09 was intended as a follow-on to RISAT-1 (which STOPPED functioning in 2017) and as a backup and enhancement to EOS-04. Its main role was to increase the frequency of SAR observations, ensuring continuous and reliable data for national security and disaster management. The loss of EOS-09 delays India’s plan to build a more robust, multi-satellite surveillance constellation.

ISRO’s Recovery Plans

ISRO has initiated a detailed technical analysis of the third-stage anomaly, suspected to be a flex nozzle control system failure, and is expected to release findings after internal and external committee reviews. Historically, ISRO’s PSLV has an excellent reliability record, with only three failures in over 60 missions, reinforcing confidence in a swift recovery.

To address the immediate gap:

ISRO may expedite the launch of a replacement satellite with similar C-band SAR capabilities.
The agency will rely on EOS-04 and other operational satellites to manage critical surveillance and disaster response needs in the interim.
Four more PSLV launches are planned for 2025, which could include a replacement for EOS-09.

Long-Term Alternatives And Strategic Shifts

The failure has highlighted the strategic need for a larger, more resilient satellite constellation. ISRO is expected to accelerate its plan for a 52-satellite surveillance network, minimizing the impact of single-mission failures in the future.

Additionally, India is increasingly involving private sector partners through initiatives like IN-SPACe, which has shortlisted consortiums to build and operate a new constellation of Earth observation satellites. This public-private partnership aims to enhance geospatial data infrastructure and foster innovation, ensuring India’s capabilities keep pace with growing civilian and defence needs.

Globally, military and commercial Earth observation programs-such as the US KH-11, France’s Helios 2, and commercial providers like MAXAR and Planet Labs-demonstrate the value of robust, multi-satellite constellations for real-time intelligence and disaster response. India’s efforts to expand its constellation and collaborate with private and international partners are aligned with these global trends, aiming to ensure strategic autonomy and rapid recovery from setbacks.

Conclusion

While the loss of EOS-09 is a significant setback, India’s existing satellite fleet, ongoing PSLV missions, and strategic plans for constellation expansion and public-private collaboration provide a clear path to recovery. ISRO’s rapid response, combined with lessons learned from this failure, is expected to strengthen India’s Earth observation capabilities in the coming years.

Agencies