The upper stage of PSLV-37 rocket, which launched a record number of 104 satellites more than seven years ago, has re-entered the earth's atmosphere as predicted, the Indian Space Research Organisation announced on Tuesday.

PSLV-C37 was launched on February 15, 2017 with Cartosat-2D as the main payload along with another 103 satellites as co-passengers. It created history as the first mission to launch 104 satellites with a single vehicle, the Bengaluru-headquartered national space agency noted in a statement.

After injecting the satellites and passivation, the upper stage (PS4) was left at an orbit of approximately 470 x 494 km size. It was regularly tracked and its orbital altitude slowly decayed, primarily due to atmospheric drag effects, it said.

Since September 2024, IS4OM (ISRO System for Safe and Sustainable Space Operations Management) regularly monitored the orbital decay as part of its regular activities and predicted the re-entry into the atmosphere in October first week. The re-entry occurred on October six. "The corresponding impact point is in the North Atlantic Ocean," it said.

"The atmospheric re-entry of the rocket body within eight years of its launch is fully compliant with the international debris mitigation guidelines, in particular, the guideline of Inter-Agency Space Debris coordination committee (IADC) that recommends limiting the post-mission orbital life of a defunct object in Low-Earth orbit (LEO) to 25 years," the statement said.

This requirement was met by properly designing a passivation sequence which lowered the orbit of PS4 after the injection of the payloads, ISRO said.

At present, special initiatives are undertaken to ensure that the residual orbital lifetime of the PSLV upper stages is reduced to five years or even less by actively de-orbiting them to lower altitude orbits through engine re-starts, as in PSLV-C38, PSLV-40, PSLV-C43, PSLV-C56, and PSLV-C58 missions, the space agency said.

Controlled re-entry of the upper stage is also envisaged for the disposal of the upper stage in future PSLV missions, it was stated.

As part of its longstanding commitment to preserve long term sustainability of outer space activities, ISRO will continue to implement proactive measures to meet the objectives of the Debris Free Space Mission by the year 2030, the statement said.

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