Isro carries out controlled re-entry of an aged satellite

MT-1 was launched on October 12, 2011, as a joint venture of Isro and the French space agency, Centre National d’Etudes Spatiales (CNES), to study tropical weather and climate.

India’s space agency successfully conducted a controlled re-entry of a decommissioned satellite -- Megha-Tropiques-1 (MT-1) -- in low earth orbit on Tuesday.

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“The satellite re-entered earth’s atmosphere and would have disintegrated over the Pacific Ocean,” the Indian Space Research Organisation (Isro) said in a statement.

MT-1 was launched on October 12, 2011, as a joint venture of Isro and the French space agency, Centre National d’Etudes Spatiales (CNES), to study tropical weather and climate. Although the mission life of the satellite was three years, it continued to provide data for more than a decade, supporting regional and global climate models till 2021, when it was finally decommissioned.

“The orbital lifetime of MT-1, weighing about 1000 kg, would have been more than 100 years in its 20-degree inclined operational orbit of 867 km altitude. About 125 kg on-board fuel remained unutilised at its end-of-mission that could pose risks for accidental break-up,” Isro said. “This leftover fuel was estimated to be sufficient to achieve a fully controlled atmospheric re-entry to impact an uninhabited location in the Pacific Ocean.”

De-orbiting a low earth orbit object at its end of life should preferably be done through controlled re-entry to a safe impact zone or by bringing it to an orbit where the orbital lifetime is less than 25 years, according to guidelines by the Inter-Agency Space Debris Coordination Committee. It is also recommended to carry out “passivation” of on-board energy sources to minimise the risk of any accidental break-up.

Controlled re-entries involve de-orbiting to very low altitudes to ensure the impact occurs within a targeted safe zone, an Isro scientist explained. “Usually, large satellites or rocket bodies, which are likely to survive aero-thermal fragmentation upon re-entry, are made to undergo controlled re-entry to limit ground casualty risk,” he said, seeking anonymity. “However, all such satellites are specifically designed to undergo controlled re-entry at end-of-life.”

An uninhabited area in the Pacific Ocean between 5°S to 14°S latitude and 119°W to 100°W longitude was identified as the targeted re-entry zone for MT1. Since August 2022, 18 orbit manoeuvres were performed to progressively lower the orbit, officials said.