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Mahesh

15/03/23 07:59 AM IST

ISRO brings down weather satellite Megha Tropiques-1

In News
  • The Indian Space Research Organisation (ISRO) recently successfully de-orbited a satellite after its end of mission.
  • Megha Trophiques-1 was brought down from its orbit as it disintegrated and burned up in the skies above the Pacific Ocean.
How ISRO Brought Down the Satellite?
  • This was the first time that the space agency attempted such a manoeuvre to clear out space debris despite the satellite not being built to do so.
  • With over 120kgs of fuel remaining in the satellite even after being decommissioned, the space agency attempted a controlled re-entry.
  • A series of 20 manoeuvres over eight months lowered the orbit of the satellite such that it re-entered the dense atmosphere and burnt up over the Pacific Ocean.
What Happens to Satellites after their Life ends?
  • Usually, satellites are left in their orbit and because of the gravitational pull of the earth, they come down to the atmosphere over years.
  • It takes debris from the low earth orbit 20 to 30 years to fall to the atmosphere and generations for those in geosynchronous or geo-stationary orbits to fall.
  • When the satellites re-enter the atmosphere, the friction causes it to heat up to extreme high temperatures of thousands of degrees Celsius.
  • Without a heat shield, 99% of a satellite gets burnt up whether in a controlled re-entry or an uncontrolled one.
  • A controlled re-entry is possible only for satellites in low-earth orbit - at about 1,000 kms over the surface of the earth.
  • These manoeuvres, however, are not usually attempted because fuel reserves have to be maintained in the satellite after mission life is over.
  • This is impossible for satellites placed in geo-stationary or geosynchronous orbit - where time taken by the satellite to orbit the earth matches Earth’s rotation - because they are at altitudes of nearly 36,000 kms.
  • For attempting to bring down a satellite from such an orbit, a huge fuel reserve would be needed, which will only make the satellite heavier and costlier at launch.
  • Therefore, instead of bringing them down, they are shot upwards at the end of life. These orbits are like parking lots in space where all old satellites are put in.
  • Sometimes a satellite might escape to deep space (when its velocity increases enough to get away from the gravitational pull of the earth) as well.
Why did ISRO Attempt a Controlled Re-entry?
  • Other than extra fuel remaining in the satellite after the mission life ended, ISRO attempted the control re-entry to demonstrate and understand the process of doing so.
  • With several satellites/other objects/debris moving at extremely high speeds in low earth orbits, it has become imperative to keep the space clean as even the smallest debris can destroy active satellites.
  • Kessler syndrome - a scenario where the amount of space debris reaches a point where they just create more with one collision triggering others - is even scarier.
  • This is the reason space debris is monitored and sometimes satellites have to be moved from their way.
Source- India Today

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