The upper stage of the PSLV-37 rocket, which launched 104 satellites seven years ago, has successfully re-entered 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 its primary payload, along with 103 co-passenger satellites.
On February 15, 2017, ISRO launched 104 satellites simultaneously for the first time from the Satish Dhawan Space Center in Sriharikota. The launch was carried out using the PSLV-C37 rocket. Since then, the upper stage of the rocket, known as PS4, had been orbiting in space after successfully releasing the satellites into their designated orbits.
After delivering the satellites, the rocket's upper stage, known as PS4, was left in orbit at an altitude of about 470 x 494 kilometers. Over time, atmospheric drag gradually reduced its orbit.
Since September 2024, ISRO’s System for Safe and Sustainable Space Operations Management (IS4OM) had been closely tracking the orbital decay of PS4 and predicted its re-entry for early October. The re-entry occurred on October 6, with the impact point located in the North Atlantic Ocean.
ISRO noted that this re-entry complies with international debris mitigation guidelines, specifically the Inter-Agency Space Debris Coordination Committee (IADC) recommendation to limit the post-mission orbital life of defunct objects in Low-Earth orbit (LEO) to no more than 25 years.
To meet these guidelines, ISRO designed a passivation sequence that lowered PS4's orbit after payload deployment. Currently, ISRO is actively working to reduce the residual orbital lifetime of PSLV upper stages to five years or less, through engine restarts in missions such as PSLV-C38, PSLV-C40, PSLV-C43, PSLV-C56, and PSLV-C58.
Future PSLV missions will include controlled re-entries to safely dispose of the upper stages. ISRO's goal is to achieve a Debris-Free Space Mission by 2030, taking proactive steps to ensure the long-term sustainability of space activities.
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