Controlled reentry experiment of MT1 Satellite

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The Indian Space Research Organisation (ISRO) successfully carried out the controlled re-entry experiment for the decommissioned Megha-Tropiques-1 (MT-1) satellite.

What is the Reentry of Satellites?

Due to the increasing number of objects in space (Space Debris), the international aerospace community has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth.
One method of post mission disposal is to allow the reentry of these spacecraft, either from natural orbital decay (uncontrolled) or controlled entry.

Methods of doing it

Orbital decay or uncontrolled: One way to accelerate orbital decay is to lower the perigee altitude so that atmospheric drag will cause the spacecraft to enter the Earth’s atmosphere more rapidly. However, in such cases the surviving debris impact footprint cannot be guaranteed to avoid inhabited landmasses.
Controlled entry normally is achieved by using more propellant with a larger propulsion system to cause the spacecraft to enter the atmosphere at a steeper flight path angle. The vehicle will then enter the atmosphere at a more precise latitude and longitude, and the debris footprint can be positioned over an uninhabited region, generally located in the ocean.

What is Space Debris?

Space debris encompasses both natural meteoroid and artificial (human-made) orbital debris. Meteoroids are in orbit about the sun, while most artificial debris is in orbit about the Earth (hence the term “orbital” debris).
Orbital debris is any human-made object in orbit about the Earth that no longer serves a useful function. Such debris includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris, and fragmentation debris.

Threats

Even tiny paint flecks can damage a spacecraft when traveling at these velocities. In fact, millimeter-sized orbital debris represents the highest mission-ending risk to most robotic spacecraft operating in low Earth orbit.
In 1996, a French satellite was hit and damaged by debris from a French rocket that had exploded a decade earlier.
On Feb. 10, 2009, a defunct Russian spacecraft collided with and destroyed a functioning U.S. Iridium commercial spacecraft. The collision added more than 2,300 pieces of large, trackable debris and many more smaller debris to the inventory of space junk.
China’s 2007 anti-satellite test, which used a missile to destroy an old weather satellite, added more than 3,500 pieces of large, trackable debris and many more smaller debris to the debris problem.

How ISRO did it?

The MT1 satellite was launched in 2011 and since August 2022, the satellite’s perigee was progressively lowered through a series of 20 manoeuvres.
The final two de-boost burns were executed on 7th March 2023, the final perigee was estimated to be less than 80 km indicating that the satellite would enter the denser layers of the Earth’s atmosphere and subsequently undergo structural disintegration.
From the latest telemetry, it is confirmed that the satellite has re-entered the Earth’s atmosphere and would have disintegrated over the Pacific Ocean, the Mission Operations Complex in ISTRAC (ISRO Telemetry, Tracking and Command Network).

Way Ahead

In recent years, ISRO has taken up proactive measures to improve the compliance level with the internationally accepted guidelines on space debris mitigation.
Efforts are underway to build indigenous capabilities for tracking and monitoring space objects to safeguard Indian space assets.
ISRO System for Safe and Sustainable Space Operations Management (IS4OM) has been established to spearhead such activities.
The controlled reentry exercise bears yet another testimony to India’s continued efforts towards ensuring the long-term sustainability of outer space activities.

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