ISRO EOS-09 mission failure: What are the alternatives for India in the Earth observation space?

On May 18, 2025, the Indian Space Research Organisation (ISRO) faced a rare setback when its 101st mission, the PSLV-C61, failed to place the Earth Observation Satellite-09 (EOS-09) into orbit. A technical glitch in the rocket’s third stage caused the mission to fail, leaving India without a key satellite meant for all-weather surveillance. What is next for India? Does India have other satellites to fill the gap? What was EOS-09 going to replace? How does ISRO plan to recover?

 

EOS-09, also known as RISAT-1B, was a 1,696 kg satellite designed to capture high-resolution images of Earth’s surface, day or night, even through clouds, rain, or fog. It used C-band Synthetic Aperture Radar (SAR) technology, which is perfect for monitoring borders, tracking natural disasters, managing agriculture, and supporting urban planning. With a one-meter imaging resolution, EOS-09 was meant to strengthen India’s security and resource management by providing real-time data.

 

The satellite was part of India’s growing constellation of Earth observation satellites, aimed at ensuring constant watch over the country’s 15,000 km of land borders and 7,500 km of coastline. Its ability to see through bad weather made it a vital tool for national security and disaster response.

 

EOS-09 was a repeat of the EOS-04 satellite, launched in 2022, and a follow-on to the RISAT-1 satellite. EOS-04, also known as RISAT-1A, is still operational and uses similar C-band SAR technology for all-weather imaging. RISAT-1, launched in 2012, was designed for a five-year mission but stopped functioning in 2017. EOS-09 was meant to enhance the frequency of observations and provide backup to EOS-04, ensuring continuous data for critical applications like border surveillance and disaster management.

 

So does India have other alternate Earth observation satellites still working? “India has several operational Earth observation satellites that can partially fill the gap left by EOS-09’s failure. ISRO’s fleet includes satellites like EOS-04 (RISAT-1A), Resourcesat, Cartosat, and RISAT-2B, which are equipped for various imaging tasks. EOS-04, in particular, shares EOS-09’s C-band SAR technology and can handle all weather surveillance, though it may not match the planned frequency of observations that EOS-09 would have provided,” explained space expert Girish Linganna.

 

Explaining further this expert says that other satellites, like those in the Cartosat series, offer high-resolution optical imaging for mapping and urban planning but struggle in cloudy or dark conditions. “RISAT-2B, with its X-band SAR, provides sharper images for military surveillance but is less suited for broader tasks like monitoring vegetation or water bodies. While these satellites ensure India’s Earth observation capabilities remain strong, the loss of EOS-09 delays plans for a more robust 52-satellite surveillance constellation,” added Linganna.

 

ISRO is already taking steps to recover from this setback. The ISRO Chairman V Narayanan, has promised a detailed technical analysis to understand the third-stage anomaly, suspected to be a flex nozzle control system failure. ISRO’s track record shows only three PSLV failures in over 60 missions since 1993, proving its reliability. Scientists are confident this is a temporary hiccup, as ISRO has four more PSLV launches planned for 2025.

 

To make up for EOS-09’s loss, ISRO may fast-track the launch of another Earth observation satellite with similar capabilities. The agency could also rely on EOS-04 and other satellites to handle urgent tasks while preparing a replacement mission. ISRO’s focus on sustainability, like including deorbiting fuel in EOS-09, shows its commitment to responsible space operations, which will continue in future missions. 

 

Experts observe that the failure also highlights the need for a larger satellite constellation. ISRO is likely to accelerate its ambitious plan to build a network of 52 surveillance satellites, ensuring no single failure disrupts India’s monitoring capabilities. Collaborations with private companies and international partners could further boost ISRO’s ability to launch replacements quickly.

 

The EOS-09 failure is a rare stumble for ISRO, which has earned global respect for its cost-effective and reliable space missions. With operational satellites like EOS-04 and a clear recovery plan, India’s ability to monitor its borders, manage disasters, and support development remains intact.

 

“Globally, military satellite programs such as the United States' KH-11 Kennen, France's Helios 2, and Israel's Ofek-13 demonstrate the strategic value nations place on exclusive defence-oriented orbital systems. The Ukraine War has further validated the indispensability of satellites in modern conflict, with commercial providers like Maxar Technologies and Planet Labs delivering real-time intelligence that has reshaped battlefield dynamics, from tracking troop movements to assessing infrastructure damage,” remarked Srimathy Kesan, Srimathy Kesan, founder and CEO of Space Kidz India.

 

She explained that the United States maintains orbital supremacy through the National Reconnaissance Office's KH-11 Kennen satellites, which achieve sub-10 cm resolution using Hubble-class optics. During the 2020 Nagorno-Karabakh conflict, KH-11 imagery exposed Turkish Bayraktar TB2 drone deployments, enabling Armenian forces to adjust defensive positions. The satellites' thermal infrared sensors additionally track missile plumes and artillery fire, as demonstrated in Ukraine, where they identified Russian S-400 battery locations near Kyiv.

 

“France's Helios 2 constellation (2A and 2B) combines 35 cm resolution visible imagery with thermal infrared sensors for night operations. During Mali's Operation Barkhane, Helios 2B monitored jihadist convoys crossing the Sahara, enabling French Mirage jets to conduct precision strikes. The system’s successor, Composante Spatiale Optique (CSO), launched in 2018, enhances this capability with 20 cm resolution and hyperspectral sensors for chemical detection,” pointed out Kesan.

 

Experts observe that the Ukraine conflict has demonstrated the democratization of space-based intelligence, with commercial providers like Maxar and Planet Labs supplying 90% of Kyiv's orbital data. Maxar's Skysat constellation (0.5 m resolution) documented the Bucha massacre within hours of its discovery, providing geolocated evidence for war crimes investigations. Planet's Dove satellites (3 m resolution) enabled daily monitoring of the Zaporizhzhia Nuclear Power Plant, detecting Russian efforts to militarize the exclusion zone.

 

The PSLV-C61 failure delays India’s INSPACe initiative, which aimed to deploy 52 surveillance satellites by 2030. The proposed GISAT-20 (2-meter resolution thermal IR) will monitor high-altitude Chinese infrastructure along the LAC, while the NISAR mission (2026), a joint venture with NASA, will deploy L-band and S-band radars for centimetre-scale deformation monitoring-critical for detecting tunnel construction beneath disputed territories. ISRO’s emphasis on controlled de-orbiting protocols for EOS-09’s PS4 stage reflects growing adherence to sustainable space practices, though the satellite’s loss leaves a gap in all-weather imaging until a replacement launches.

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