Bengaluru, March 6 (PTI) The Indian Space Research Organization (ISRO) on Tuesday is gearing up for a “very challenging” test to re-enter a defunct orbiting satellite.

The low Earth satellite, Megha-Tropiques-1 (MT1), was launched on October 12, 2011, as a joint satellite initiative of ISRO and the French space agency CNES, for tropical weather and climate studies.

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 target re-entry zone for MT1, which weighs about 1000 kg.

About 125 kg of fuel was left unused at its end, which could pose a risk of accidental breakdown, the ISRO report noted.

This residual fuel was estimated to be sufficient to achieve fully controlled atmospheric re-entry affecting uninhabited areas in the Pacific Ocean.

Controlled re-entry involves circling to a very low altitude to ensure impact is within the targeted safe zone.

Usually, large satellites/rocket bodies that can survive air-thermal fragmentation during re-entry are subjected to controlled re-entry to limit the risk of ground accidents.

However, all such satellites are designed to undergo controlled re-entry at EOL.

“MT1 was not designed for EOL operations with controlled re-entry, which made the entire exercise very challenging,” ISRO said.

Also, the in-flight constraints of the aging satellite, where many systems have lost redundancy and shown degraded performance, and maintaining subsystems much lower than originally designed orbital altitudes under harsh environmental conditions, have added to operational problems.

Innovative solutions were implemented by the operational team based on study, consultations and exchanges between mission, operations, flight dynamics, aerodynamics, propulsion, controls, navigation, thermal and other subsystem design teams working at ISRO centers. In coordination to overcome these challenges.

Since August 2022, 18 orbital maneuvers have been performed to gradually lower the orbit. Between orbits, aero-braking studies were performed at different solar panel orientations to gain better insights into the physical process of atmospheric drag affecting the satellite’s orbital deformation.

The final de-boost strategy is designed considering several constraints including re-entry track visibility at ground stations, ground impact within the target zone and allowable operating conditions of the subsystems, particularly the maximum deliverable thrust and max. Firing duration of impulses.

The final two T-boost burns and ground impact will take place on March 7 between 16:30 IST and 19:30 IST, ISRO said.

Aero-thermal simulations show that none of the large fragments of satellites are likely to retain aerothermal heat during re-entry.

Although the satellite’s mission was initially for three years, it has provided valuable data services for more than a decade supporting regional and global climate models till 2021, the Bangalore-headquartered National Space Agency said.

The UN/IADC (Inter-Agency Space Debris Coordination Committee) space debris mitigation guidelines require LEO (Low Earth Orbit) material to be disposed of at the end of its life (EOL), by controlled re-entry to a safe impact zone, or to an orbit whose orbital lifetime is less than 25 years, according to ISRO. By bringing.

It is also recommended to carry out “inactivity” of on-board energy sources to reduce the risk of accidental breakdown after work.

According to ISRO, MT1’s orbital lifetime would have been more than 100 years in its 20-degree inclined operational orbit at an altitude of 867 km.

“As a responsible space agency to ensure safe and sustainable operations in space, ISRO is leading efforts to better comply with the UN/IATC Space Debris Mitigation Guidelines in disposal of LIO material,” the statement said.

The re-entry test of MT1 has been undertaken as part of the ongoing efforts as this satellite with sufficient residual fuel provided a unique opportunity to test the relevant mechanisms and understand the operational nuances associated with de-missioning the mission through direct re-entry. In the Earth’s atmosphere, it was said. PTI RS ROH ROH

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