PSLV-37 rocket's upper stage re-enters Earth's atmosphere right on schedule: ISRO

The upper stage of the PSLV-37 rocket, which launched 104 satellites seven years ago, has re-entered the earth's atmosphere, according to the Indian Space Research Organisation (ISRO). The PSLV-C37 mission was launched on February 15, 2017, with Cartosat-2D as the main payload and 103 co-passenger satellites.

ISRO explained that after delivering the satellites, the upper stage, known as PS4, was left in orbit at approximately 470 x 494 kilometers. Over time, its orbital altitude reduced mainly due to atmospheric drag.

Since September 2024, ISRO's System for Safe and Sustainable Space Operations Management (IS4OM) tracked the orbital decay of PS4 and predicted its re-entry into the atmosphere in early October. On October 6, the re-entry occurred with the impact point being in the North Atlantic Ocean.


ISRO stated, "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."

ISRO achieved this by designing a passivation sequence that lowered PS4's orbit after deploying the payloads. Currently, ISRO is taking steps to reduce the residual orbital lifetime of PSLV upper stages to five years or less through engine re-starts, as seen in PSLV-C38, PSLV-40, PSLV-C43, PSLV-C56, and PSLV-C58 missions.

Future PSLV missions plan to include controlled re-entry for upper stage disposal. ISRO aims to achieve a Debris Free Space Mission by 2030 through proactive measures to ensure the long-term sustainability of outer space activities.