Four spherical metal balls fell from the sky in some villages of Gujarat over the past few days.
Some experts say they are most likely the debris of a Chinese rocket Chang Zheng 3B or fuel storage tanks of space launch vehicles.
With more & more space launches and events like space tourism kicking off, the space above Earth is overcrowded – calling for urgent attention from countries to declutter it.

Space junk, or space debris, is any piece of machinery or debris left by humans in space.
It can refer to big objects such as dead satellites that have failed or been left in orbit at the end of their mission.
It can also refer to smaller things, like bits of debris or paint flecks that have fallen off a rocket.
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).

All space junk is the result of us launching objects from Earth, and it remains in orbit until it re-enters the atmosphere.
Some objects in lower orbits of a few hundred kilometres can return quickly.
They often re-enter the atmosphere after a few years and, for the most part, they’ll burn up – so they don’t reach the ground.
But debris or satellites left at higher altitudes of 36,000 kilometres – where communications and weather satellites are often placed in geostationary orbits – can continue to circle Earth for hundreds or even thousands of years.
Some space junk results from collisions or anti-satellite tests in orbit.

While there are about 2,000 active satellites orbiting Earth at the moment, there are also 3,000 dead ones littering space.
What’s more, there are around 34,000 pieces of space junk bigger than 10 centimetres in size and millions of smaller pieces that could nonetheless prove disastrous if they hit something else.

Fortunately, at the moment, space junk doesn’t pose a huge risk to our exploration efforts.

Collisions: Collisions could cause significant damage to the space properties of the countries. Upon collision, the debris disables the satellites’ onboard electronics and may disrupt the services provided by the space assets.
Collateral damage: The biggest danger it poses is to other satellites in orbit. These satellites have to move out of the way of all this incoming space junk to make sure they don’t get hit and potentially damaged or destroyed.
High momentum strikes: As these debris travel at high speeds in the low earth orbit, they risk colliding with functional satellites or even the space station. Given that these particles travel at speeds of 8 metres per second, even a 100g object could create an impact comparable to a 30-kg stone travelling at 100kmph.
Usability of space: This debris orbit the earth several times a day. As the mass of space junk continues to grow, parts of the space may become unusable.
Kessler Syndrome: It refers to a theoretical scenario in which the amount of space debris becomes so high that a single collision or destruction event could lead to a snowballing cascade of space debris- like a domino effect.

India had 103 spacecraft, including active and defunct satellites, and 114 space debris objects, including spent rocket bodies orbiting the earth.
So, the country has a total of 217 space objects orbiting the earth.
Presently, the ISRO has taken up research activities to study the feasibility and technologies required to undertake active debris removal (ADR).
ADR was one of the active methods suggested by the Space Debris Research Community to contain the growth of space debris objects.

Space is beyond national jurisdiction and falls under the ambit of international law:

Under the Convention on International Liability for Damage Caused by Space Objects, countries can claim compensation from other countries for damages incurred from space debris.
The Outer Space Treaty, 1967 and the like outline the guidelines for the countries’ activities in space.
All space objects, including the defunct space debris, are under the jurisdiction of the ‘State of Registry’.
If something goes wrong during such manoeuvres, a liability regime under the applicable international law applies to not only the launching country but also other countries involved in the launch.
The UN Committee on the Peaceful Use of Outer Space (COPUOS) is tasked with space governance and there are already accepted guidelines for space debris mitigation and sustainability of space activities.

There are four techniques that can move debris from heavily trafficked orbits:

Deorbiting (the deliberate, forced re-entry of a space object into the Earth’s atmosphere by application of a retarding force, usually via a propulsion system)
Orbital lifetime reduction (accelerating the natural decay of spacecraft and other space objects to reduce the time that they remain in orbit)
Disposal orbits– Moving objects into less populated “disposal” orbits at the end of their functional lifetime
Active removal of debris from orbit

Global efforts

NASA undertakes DAMs or Debris Avoidance Manoeuvres, which are navigation manoeuvres that take the space station away from its normal trajectory to avoid collisions, are undertaken based on the probability of collision.
NORAD, or the North American Aerospace Defence Command, is an initiative of the U.S. and Canada that shares selective debris data with many countries.
Clearspace-1 (of European Space Agency), which is scheduled to launch in 2025, will be the first space mission to eliminate debris from orbit.

India’s efforts: Project NETRA

NETRA stands for Network for Space Objects Tracking and Analysis (NETRA) project.
Project NETRA is an early warning system in space to detect debris and other hazards to Indian satellites.
In this pursuit, space debris tracking radar with a range of 1,500 km and an optical telescope will be inducted as part of establishing an effective surveillance and tracking network under NETRA.

Space junk is no one country’s responsibility, but the responsibility of every spacefaring country.
Spacefaring nations must minimize the risks to people and property on Earth of re-entries of space objects and maximize transparency regarding those operations.
High-accuracy assessment and prediction tools are essential for reducing risk to current systems and future launches.
Space traffic management is a crucial area that requires attention since the satellites in orbit can come in the way of each other.

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