POEM-4 re-enters Earth's atmosphere: ISRO

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.

“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’.

The safe re-entry of POEM-4 is yet another accomplishment of ISRO’s commitment to contain the growth of space debris, reaffirming the prominent role of the space agency in the long-term sustainability of outer space environment and Debris Free Space Mission (DFSM), it said.

On December 30, 2024, ISRO’s PSLV-C60 launched twin SPADEX (Space Docking Experiment) 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 almost in the same orbit.

Noting that subsequently, POEM-4 was de-orbited by engine restarts to a nearly circular orbit at 350 km altitude with 55.2 inclination, ISRO said, the PS4 was then passivated by venting the leftover fuel to minimise any potential risk for accidental break-up.

“During its mission life, POEM-4 hosted altogether 24 payloads (14 payloads from ISRO and 10 from various NGEs) and all payloads worked as expected yielding valuable science data,” it said.

While the POEM-4 was in orbit, it was continuously tracked by ISRO’s Radar Facilities and United States Space Command (USSPACECOM) facilities as well.

The tracking data was in turn utilised in the re-entry prediction process, ISRO said, adding that it was observed that POEM-4’s orbit had decayed to 174 kmx165 km and the platform was predicted to re-enter the Earth’s atmosphere on April 04, 2025.

The atmospheric re-entry event of POEM-4 was then closely monitored by ISRO System for Safe and Sustainable Space Operations Management (IS4OM) and regular updates in predictions were made, it added.