The Indian Space Research Organisation (ISRO) and the French space agency, CNES, are collaborating to study and analyse the movement of Megha-Tropiques-1 (MT1) as it re-enters Earth's atmosphere on March 7. The satellite was launched in 2011 to conduct tropical weather and climate studies, and it continued to provide valuable data services for more than a decade before the decision was made to decommission it and burn it into the atmosphere. ISRO has selected an uninhabited area in the Pacific Ocean as the targeted re-entry zone for MT1, and the space agency has performed 18 orbit maneuvers since August 2022 to progressively lower the orbit of the defunct spacecraft.
The decision to crash the satellite was taken following space debris mitigation guidelines set by the United Nations Inter-Agency Space Debris Coordination Committee (UNIADC). These guidelines state that the satellite should be deorbited 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 is less than 25 years. The guidelines also recommend carrying out the “passivation” of onboard energy sources to minimize the risk of any post-mission accidental break-up.
During its service life, MT1 supported regional and global climate models until 2021, providing valuable insights into tropical weather patterns and the climate in the region. The satellite's re-entry is part of a broader effort to address the growing problem of space debris surrounding Earth, which makes observations difficult and increases the risk of collisions in zero gravity.
The decision to crash MT1 is a significant step forward in space debris mitigation efforts, as it provides an opportunity to test relevant methodologies and operational nuances of post-mission disposal by direct re-entry into Earth's atmosphere. ISRO has been vocal about the issues of space junk and the need for sustainability in low Earth orbit. The agency has performed aero-braking studies at different solar panel orientations to gain a better understanding of the physical process of atmospheric drag affecting the orbital decay of the satellite.
The final de-boost strategy for MT1 has been designed with several constraints in mind, including visibility of the re-entry trace over ground stations, ground impact within the targeted zone, and allowable operating conditions of subsystems, especially the maximum deliverable thrust and the maximum firing duration of the thrusters. The final two de-boost burns followed by the ground impact are expected to take place between 16:30 IST to 19:30 IST on March 7.
ISRO has stated that aero-thermal simulations have shown that no large fragments of the satellite are likely to survive the aerothermal heating during the re-entry, ensuring that the debris generated will not pose any danger to other satellites or spacecraft. The collaboration between ISRO and CNES in the MT1 re-entry experiment is an example of international cooperation in space exploration and research, and it sets a precedent for sustainable space exploration practices in the future.