ISRO module POEM-4, from SpaDeX Mission, re-enters earth’s atmosphere

The Indian Space Research Organisation (ISRO) has revealed that 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 (SpaDeX) Mission, has re-entered Earth’s atmosphere.

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“Finally, the POEM-4 module re-entered the atmosphere and impacted at 2.33 UTC (8.03 IST), on April 4, in the Indian Ocean,” ISRO said on X.

It said the safe re-entry of POEM-4 was 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).

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 almost in the same orbit. 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 24 payloads — 14 payloads from ISRO and 10 from various non-government entities (NGEs). All of these payloads worked as expected, yielding valuable science data,” it said.

While the POEM-4 was in the orbit, it was continuously tracked by ISRO’s Radar Facilities and United States Space Command (USSPACECOM) facilities. 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 km x 165 km and the platform was predicted to re-enter the Earth’s atmosphere on April 4.

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 were made in predictions, it added.