ISRO’s POEM-4 Re-Enters Earth's Atmosphere, Setting New Benchmarks in Space Sustainability

In a significant stride towards sustainable space missions, the Indian Space Research Organisation (ISRO) announced the successful re-entry of the PSLV Orbital Experimental Module (POEM-4) into Earth’s atmosphere on April 4, 2025, at 02:33 UTC (08:03 IST). The module safely disintegrated over the Indian Ocean, marking a critical achievement in India’s ongoing efforts to tackle the growing issue of space debris.

What is POEM-4?

POEM-4 was the repurposed fourth stage of the PSLV-C60 rocket, which was launched on December 30, 2024. Unlike traditional upper stages that are often left in orbit as space junk, ISRO converted POEM-4 into a fully operational orbital platform for conducting in-space experiments. During its mission, it carried 24 payloads—14 developed by ISRO and 10 from other Indian and international institutions—making it a compact yet versatile lab in orbit.

Among the major payloads were SPADEX (Space Docking Experiment) twin satellites, designed to demonstrate autonomous docking capabilities, a key future requirement for space stations and satellite servicing.

Technical Specifications of POEM-4

• Platform: PSLV-C60 fourth stage (PS4) converted to POEM

• Launch Date: December 30, 2024

• Initial Orbit: 475 km circular orbit

• Payloads: 24 total (14 ISRO, 10 others)

• Re-entry Date & Time: April 4, 2025 | 02:33 UTC / 08:03 IST

• Re-entry Orbit before Impact: 174 km x 165 km

• Impact Zone: Indian Ocean

• De-Orbiting Method: Controlled engine restart to 350 km followed by natural orbital decay

Commitment to Clean Space

The successful de-orbiting and controlled re-entry of POEM-4 is part of ISRO’s broader Debris Free Space Mission (DFSM). This initiative reflects India’s alignment with international best practices for space sustainability, including passivation—a critical step where leftover fuel is vented to prevent accidental explosions or breakups in orbit.

POEM-4's descent was precisely tracked and monitored by ISRO's System for Safe and Sustainable Space Operations Management (IS4OM) along with support from the United States Space Command, ensuring that the module’s path and impact location posed no threat to human life or active satellites.

A Step Towards the Future

ISRO’s POEM initiative not only serves as an eco-friendly approach to space operations but also provides a low-cost platform for research and development in microgravity conditions. By giving a second life to rocket stages, ISRO is opening new avenues for scientific innovation without adding to space congestion.

The success of POEM-4 sets the stage for future POEM missions and underlines India's growing expertise in responsible space management. As ISRO prepares for more ambitious missions—ranging from Gaganyaan to planetary explorations—initiatives like POEM show that India’s space program is not just advancing technology, but also leading the way in ethical and sustainable space exploration.