PSLV-XL | EOS-09 (RISAT-1B)
PSLV-XL • PSLV
📝 Mission Description
ISRO's PSLV-XL Launches EOS-09 (RISAT-1B): Advancing All-Weather Earth Observation
On May 18, 2025, the Indian Space Research Organisation (ISRO) successfully launched the EOS-09 satellite, also known as RISAT-1B, aboard its reliable Polar Satellite Launch Vehicle (PSLV-XL) from the Satish Dhawan Space Centre in Sriharikota. This mission marks a significant step in enhancing India's radar imaging capabilities, building on the legacy of the RISAT-1 series. As the third satellite in this lineup, RISAT-1B promises to deliver critical data for civilian and defense applications, underscoring ISRO's growing prowess in space technology.
At the heart of the mission are the objectives centered on all-weather, day-and-night Earth observation. RISAT-1B features an active C-band Synthetic Aperture Radar (SAR) payload, which operates independently of sunlight and cloud cover, making it invaluable for monitoring dynamic environmental changes. The satellite's capabilities extend to a wide array of applications, including agriculture for crop health assessment, forestry for deforestation tracking, soil moisture analysis to aid irrigation planning, and geological surveys for resource mapping. It also supports coastal monitoring to detect erosion and sea ice dynamics, object identification for urban planning, and flood monitoring to enable rapid disaster response. In military contexts, its high-resolution imaging bolsters surveillance and reconnaissance, providing strategic advantages in border security and maritime domain awareness. The spacecraft's 3-axis stabilized bus, designed as a hexagonal prism around a central cylinder, integrates subsystems efficiently, with solar panels mounted on a cube-shaped section to ensure sustained power. Weighing approximately 615 kg, RISAT-1B orbits at an altitude of about 536 km in a sun-synchronous path, offering revisit times as short as 25 days for targeted areas.
The launch vehicle, PSLV-XL, is a four-stage rocket renowned for its versatility and precision. Standing 44 meters tall and weighing 320 tons at liftoff, it employs a combination of solid and liquid propulsion systems. The first stage uses a solid rocket motor augmented by six strap-on boosters, providing the initial thrust, while the second and fourth stages rely on liquid hypergolic propellants for fine-tuned orbital insertion. The third stage is solid-fueled, contributing to the vehicle's ability to place payloads up to 1,750 kg into low Earth orbit. Technical specifications include a payload fairing diameter of 3.
ℹ️ Official Details
RISAT-1B is the third in the series of radar imaging RISAT-1 satellites of ISRO using an active C-band SAR (Synthetic Aperture Radar), providing all-weather as well as the day-and-night SAR observation capability in applications such as agriculture, forestry, soil moisture, geology, sea ice, coastal monitoring, object identification, and flood monitoring, in addition to military surveillance.
The RISAT-1 series is developed, manufactured and integrated by ISRO. The 3-axis stabilized spacecraft bus consists of a hexagonal prism shape build around a central cylinder. Most of the spacecraft subsystems and the payload are integrated in the prism structure and the central cylinder. The solar panels and some subsystems are mounted on the cube-shaped section of the spacecraft.
🎯 Post-Launch Analysis
The PSLV-XL launch of EOS-09 (RISAT-1B) on May 18, 2025, encountered significant challenges as the launch vehicle experienced technical anomalies during ascent. This prevented the successful deployment of the RISAT-1B satellite, designed for all-weather, day-and-night C-band SAR imaging for applications like agriculture, forestry, and military surveillance. The failure to achieve the intended orbit marks a setback for ISRO’s radar imaging program. Preliminary analysis suggests issues in the ascent phase, though detailed investigations are underway to pinpoint the root cause. Key engineering outcomes remain inconclusive until the anomaly is fully understood, but this incident underscores the need for enhanced reliability in launch systems. For future missions, ISRO will likely prioritize rigorous pre-launch testing and anomaly resolution to ensure the PSLV-XL’s robustness, maintaining confidence in its role as a workhorse for critical Earth observation payloads.