Bengaluru:ISRO on Friday said the fourth edition of the PSLV Orbital platform Experiment Module (POEM-4), the repurposed spent upper stage of the Polar Satellite Launch Vehicle used for the space docking experiment mission, has re-entered the Earth’s atmosphere.

The module re-entered Earth’s atmosphere and impacted safely in the Indian Ocean at 02:33 UTC (08:03 IST) on April 4, 2025, ISRO confirmed in a post on social media platform ‘X’.

“Finally, the POEM-4 module re-entered the atmosphere and impacted at 02:33 UTC (08:03 IST), April 04, 2025, in the Indian Ocean,” ISRO said in a post on ‘X’.

Describing the re-entry as a milestone, ISRO said the event showcases its ongoing commitment to reducing space debris and supporting the long-term sustainability of outer space through its Debris Free Space Mission (DFSM).

Atmospheric Re-entry of POEM-4

On December 30, 2024, ISRO’s PSLV-C60 launched twin SPADEX satellites and after injecting satellites at 475 km altitude, the specially configured upper stage (PS4) of PSLV-C60 (called PSLV Orbital Experimental Module in short POEM-4) was also… pic.twitter.com/teQGV5EASx

— ISRO (@isro) April 4, 2025

POEM-4 was initially launched on December 30, 2024, as part of the PSLV-C60 mission, which successfully deployed twin SPADEX satellites at an altitude of 475 km. Following satellite deployment, the specially adapted upper stage—designated as POEM-4—remained in orbit for experimental purposes.

The module was later de-orbited through engine restarts, bringing it to a nearly circular orbit at 350 km altitude with a 55.2° inclination. In a critical step to ensure safety, ISRO passivated the upper stage by venting out any leftover fuel, thereby reducing risks of accidental break-up.

Throughout its operational period, POEM-4 hosted 24 payloads, including 14 from ISRO and 10 from non-governmental entities (NGEs). All the onboard instruments functioned successfully, generating significant scientific data.

ISRO, in collaboration with the United States Space Command (USSPACECOM), closely tracked POEM-4 during its time in orbit. As the module’s orbit decayed to 174 km x 165 km, predictions pointed to an imminent atmospheric re-entry on April 4. The process was diligently monitored by ISRO’s System for Safe and Sustainable Space Operations Management (IS4OM), ensuring a controlled and safe descent.

This event highlights ISRO’s leadership in responsible space practices, setting an example for sustainable space operations worldwide.

(With PTI inputs)