How ISRO successfully carried out the re-entry of defunct satellite
ISRO successfully carried out the "challenging" experiment of controlled re-entry of the decommissioned low-Earth orbit (LEO) satellite, called Megha-Tropiques-1 (MT-1), on March 7. The satellite re-entered the Earth's atmosphere and would have disintegrated over the Pacific Ocean, confirmed the space agency via Twitter. The entire process was tracked from the Mission Operations Complex in ISTRAC (ISRO Telemetry, Tracking, and Command Network), Bengaluru.
Why does this story matter?
The MT1 mission was a joint effort by ISRO and the French space agency Centre National d'Etudes Spatiales (CNES), for tropical weather and climate studies. During the mission, MT1 passed over India almost a dozen times every day, providing an almost real-time assessment of the evolution of clouds. The satellite, which launched in October 2011, was terminated about a decade later in December 2021.
Final de-boost burns occurred at 4:32 pm and 6:21 pm
The final two de-boost burns were executed at 4:32pm and 6:21pm IST, respectively on March 7 by firing the on-board four 11 Newton thrusters for about 20 minutes each. The final perigee—the point in the satellite's orbit where it is closest to Earth—was estimated to be less than 80km implying that the MT1 satellite would enter denser layers of Earth's atmosphere and subsequently disintegrate.
Simulations revealed there will be no surviving satellite debris
Simulations revealed that there will not be any surviving large debris from the satellite. Latest telemetric reports have confirmed that the satellite re-entered Earth's atmosphere and would have disintegrated over the Pacific Ocean. The final impact region is predicted to be in the deep Pacific Ocean and within the expected latitude and longitude boundaries.
20 maneuvers were performed to progressively lower the satellite's orbit
Since August 2022, the satellite's perigee was progressively lowered via a sequence of 20 maneuvers, a process that consumed 120kg of fuel. The maneuvers were monitored to ensure that there would be no post-maneuver close approaches with other space objects, such as the International Space Station and the Chinese Space Station as well as orbiting satellites.
Constraints included visibility of the re-entry trace over ground stations
Several maneuvers, which also include the final de-boost strategy, were designed after taking into consideration the various constraints. These include "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 constraint on thrusters," said ISRO in a statement.
