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ISRO to undertake controlled re-entry experiment of decommissioned satellite

The Indian Space Research Organization (ISRO) will be undertaking a challenging experiment of a controlled re-entry of the decommissioned Megha-Tropiques-1 (MT1) satellite on March 7. The MT1 is a joint Indo-French satellite launched in 2011 for tropical weather and climate studies which was providing data services, supporting regional and global climate models till 2021.

The space agency on Sunday said that as a responsible space agency committed to safe and sustainable operations in the outer space it was gearing up for this challenging experiment.

The ISRO said that the United Nations/Inter-Agency Space Debris Coordination Committee space debris mitigation guidelines recommended deorbiting a Low Earth Orbit object at its end-of-life, preferably through controlled re-entry to a safe impact zone, or by bringing it to an orbit where the orbital lifetime was less than 25 years.

The guidelines also recommended to carry out passivation of on-board energy sources to minimize the risk of any post-mission accidental break-up.

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“The orbital lifetime of MT1, weighing about 1,000 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 unutilized at its end-of-mission that could pose risks for accidental break-up. This left-over fuel was estimated to be sufficient to achieve a fully controlled atmospheric re-entry to impact an uninhabited location in the Pacific Ocean. Controlled re-entries involve deorbiting to very low altitudes to ensure impact occurs within a targeted safe zone,” the ISRO said.

Limiting ground casualty risk

The ISRO further said that usually, large satellites and rocket bodies which were likely to survive aero-thermal fragmentation upon re-entry were made to undergo controlled re-entry to limit ground casualty risk.

“However, all such satellites are specifically designed to undergo controlled re-entry at end-of-life. MT1 was not designed for end-of-life operations through controlled re-entry which made the entire exercise extremely challenging.

Furthermore, the on-board constraints of the aged satellite, where several systems had lost redundancy and showed degraded performance, and maintaining subsystems under harsher environmental conditions at much lower than originally designed orbital altitude added to the operational complexities,” the ISRO said.

An uninhabited area in the Pacific Ocean between 5°S to 14°S latitude and 119°W to 100°W longitude has been identified as the targeted re-entry zone for the MT1. Since Aug 2022, 18 orbit manoeuvres have been performed to progressively lower the orbit and on March 7 the ground impact is expected to take place between 4.30 p.m. and 7.30 p.m. IST.

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