Description
The Indian Space Research Organization (ISRO) is preparing for a challenging controlled reentry experiment of a decommissioned low-Earth orbit satellite, Megha-Tropiques-1 (MT1), on March 7. MT1 was launched on October 12, 2011 as a satellite joint venture by ISRO and the French space agency CNES for tropical weather and climate studies. Although the satellite's mission lifetime was originally three years, the satellite has continued to provide valuable data services for more than a decade supporting regional and global climate models until 2021, the Bangalore-based space agency said in a statement on Sunday. ALSO READ: ISRO-NASA-built satellite set to be sent to India for launch
The UN/IADC (Inter-Agency Space Debris Coordination Committee) Space Debris Mitigation Guidelines recommend deorbiting an end-of-life (LEO) LEO (low Earth orbit) object, preferably by controlled re-entry into a safe impact zone, or by taking it to an orbit where the orbital lifetime is less than 25 years, according to ISRO. It is also recommended to carry out a "passivation" of the power sources on board to minimize the risks of accidental breakage post-mission.
The orbital life of MT1, with a weight of about 1,000 kilograms, would have been more than 100 years in its operational orbit inclined 20 degrees at 867 km altitude. Approximately 125 kg of fuel on board remained unused at the end of the mission, which could present risks of accidental disintegration. It was estimated that this remaining fuel would be sufficient to achieve a fully controlled atmospheric re-entry to impact an uninhabited location in the Pacific Ocean.
Controlled reentries involve deorbiting at very low altitudes to ensure that the impact occurs within a specific safe zone. Large satellites/rocket corps likely to survive aerothermal fragmentation during re-entry are generally subject to controlled re-entry to limit the risk of casualties on the ground. However, all of these satellites are specifically designed to undergo controlled re-entry at EOL. MT1 was not designed for EOL operations via controlled re-entry, which made the entire exercise extremely challenging.
In addition, the limitations aboard the aging satellite, where several systems had lost redundancy and exhibited degraded performance, and the maintenance of subsystems in harsher environmental conditions at an orbital altitude much lower than originally designed added challenges and operational complexities. The operations team implemented innovative solutions based on study, deliberation, and discussion among mission design, operations, flight dynamics, aerodynamics, propulsion, controls, navigation, thermal, and other subsystems in the ISRO centers, which worked in synergy. to overcome these challenges.
An uninhabited area in the Pacific Ocean between 5 degrees south and 14 degrees south latitude and 119 degrees west and 100 degrees west longitude has been identified as the target re-entry area for MT1. Since August 2022, 18 orbital maneuvers have been carried out to gradually lower the orbit. Between deorbits, aerodynamic braking studies were also performed at different solar array orientations to better understand the physical process of atmospheric drag that affects the orbital decay of the satellite.
The final deboost strategy was designed after considering several constraints, including the visibility of the re-entry trail at ground stations, the impact on the ground in the target area, and the allowable operating conditions of the subsystems, in particular, the maximum available thrust. and the maximum power. propellant firing time. The last two deboost burns followed by ground impact are expected to occur between 4:30 pm and 7:30 pm on March 7. Simulations show that no large fragments of the satellites should survive aerothermal heating during re-entry.
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"As a responsible space agency committed to safe and sustainable operations in outer space, ISRO is making proactive efforts for better compliance with the UN/IADC Space Debris Mitigation Guidelines on space debris. 'Disposal of LEO objects after launch mission', the statement read.
The MT1 re-entry experiment was carried out as part of ongoing efforts, as this satellite with sufficient fuel remaining presented a unique opportunity to test relevant methodologies and understand the associated operational nuances of post-mission disposal via direct re-entry. to the earth's atmosphere. it's been said
