India’s first controlled deorbit of a spacecraft – it was safely sunk off the coast of Australia

The Indian Space Research Organisation (ISRO) confirmed that it performed a controlled deorbit of the POEM-4 spacecraft on 4 April 2025. It was launched into space on 31 December 2024 along with a pair of spacecraft simulators for the SpaDeX experiment. The module carried 24 payloads for a range of experiments. To avoid adding to the volume of space debris in orbit, the vehicle was dumped in the Indian Ocean after its work was completed.

Image source: ISRO

«The safe return of POEM-4 to Earth is yet another achievement by ISRO in its efforts to curb the growth of space debris, reaffirming ISRO’s important role in the long-term sustainability of the space environment and the space debris clearance mission,” the agency said.

The deorbiting of the spacecraft was performed by the booster block of the Indian PSLV-C60 rocket. The module remained attached to the block the entire time. It would seem that nothing could be simpler. But the operation required restarting the booster block engines, correcting the trajectory and dumping excess fuel before entering the dense layers of the atmosphere. Restarting a chemical fuel engine in a vacuum three months after shutting down is a serious scientific and technical achievement in itself, and India has proven that it is capable of it.

The location of the Indian module’s sinking

The spacecraft simulators for the SpaDeX experiment remain in orbit for about two years. The experiment was India’s first automated docking in space. Two 220-kg spacecraft simulators were built for SpaDeX. Once in orbit, one maneuvered to safely approach the other and then dock automatically.

The docking took place on January 16, 2025, making India the fourth country in history to perform an automatic docking in space. This option will be needed for the launch of India’s first manned spacecraft with astronauts in 2026, for lunar missions, and, in general, for future Indian space programs.