NEW DELHI: The Indian Space Research Organisation (Isro) will on Tuesday attempt an exceptionally difficult controlled re-entry of a decommissioned satellite.About the satelliteThe low Earth satellite, Megha-Tropiques-1 (MT1), was introduced on October 12, 2011, as a joint satellite venture of Isro and the French area company, CNES, for tropical weather condition and climate studies.Although the mission life of the satellite was initially three years, the satellite continued to supply valuable information services for more than a years supporting regional and worldwide climate models till 2021.
Why is it being deorbited?The Inter-Agency Space Debris Coordination Committees standards on space debris mitigation advise deorbiting a Low Earth Orbit things at its end-of-life (EOL), preferably through managed re-entry to a safe impact zone, or by bringing it to an orbit where the orbital lifetime is less than 25 years.The orbital lifetime of MT1, weighing about 1,000 kilograms, would have been more than 100 years in its 20 degree inclined operational orbit of 867 km altitude.
About 125 kg on-board fuel stayed unutilised at its end-of-mission that might position dangers for accidental break-up.
This remaining fuel was estimated to be sufficient to achieve a fully-controlled atmospheric re-entry.
Why is it a challenge?Usually, big satellites/rocket bodies, which are likely to endure aero-thermal fragmentation upon re-entry, are made to go through regulated re-entry to restrict ground casualty threat.
However, all such satellites are specifically developed to go through regulated re-entry at EOL.
MT1 was not designed for EOL operations through controlled re-entry which makes the whole workout exceptionally tough , ISRO said.Furthermore, the on-board restrictions of the aged satellite, where a number of systems had lost redundancy and revealed degraded performance, and keeping subsystems under harsher environmental conditions at much lower than initially developed orbital elevation contributed to the operational complexities.The re-entry experiment of MT1 has actually been undertaken as part of the ongoing efforts as this satellite with adequate leftover fuel presented a special opportunity to test the pertinent methodologies and understand the associated operational subtleties of post mission disposal by direct re-entry into the Earths environment, Isro stated.What can go wrong?Controlled reentry of a satellite is a complex and dangerous procedure, especially when the satellite is not developed for the procedure.
Some of the prospective risks associated with a regulated reentry of a satellite consist of: Uncontrolled trajectory: During the reentry procedure, the satellite should follow a specific trajectory to guarantee that it lands in a designated location.
If there are any breakdowns or mistakes in the guidance system, the satellite may deviate from its intended trajectory, potentially threatening populated areas.Structural damage: The extreme heat created during reentry can cause the satellites structure to deteriorate or break apart, increasing the threat of particles falling to the ground.Toxic materials: Some satellites might include dangerous products, such as radioactive isotopes or toxic chemicals.
If these products are not effectively contained throughout reentry, they could posture a substantial health risk to people and the environment.Electrical breakdowns: The severe heat and electro-magnetic radiation produced throughout reentry can cause electrical malfunctions in the satellites systems, possibly resulting in a loss of control or communication.Communication failure: During the reentry procedure, it is necessary for the ground control team to maintain communication with the satellite to guarantee that it is following the right trajectory.
If there is an interaction failure, it might be tough or difficult to control the satellites descent.Weather conditions: Weather conditions such as strong winds, storms, or turbulence can affect the satellites trajectory and increase the risk of it deviating from its intended path.Where is the effect zone?An unoccupied area in the Pacific Ocean in between 5 S to 14 S latitude and 119 W to 100 W longitude was determined as the targeted re-entry zone for MT1.Over 7 months of planning, adjustmentsSince August 2022, 18 orbit manoeuvres were performed to gradually reduce the orbit of the satellite.
In in between the de-orbiting, aero-braking studies at various photovoltaic panel orientations were likewise performed to get better insights into the physical process of atmospheric drag impacting the orbital decay of the satellite.When will ground effect happen?The final de-boost strategy has been designed after thinking about several constraints, including exposure of the re-entry trace over ground stations, ground effect within the targeted zone, and allowable operating conditions of subsystems, specifically the maximum deliverable thrust and the maximum firing period of the thrusters.The last 2 de-boost burns followed by the ground impact are anticipated to occur between 16.30 hours to 19.30 hours on March 7.
Simulations show that no big fragments of the satellites are most likely to make it through the aerothermal heating throughout the re-entry.(With inputs from agencies)