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What constitutes space debris and why they need our attention

Human journey into space began in 1957, when the Soviet Union (today’s Russia) launched Sputnik, the first ever artificial satellite. Since then, thousands of rockets have been launched, which have put into space numerous satellites, spacecraft, and space stations. Not all of them are functional today, nor has everything been brought back to Earth. Several of them, their parts, and random objects such as nuts and bolts are still up there as space junk. Worse, they are tumbling through space at a high speed putting functional satellites in Low Earth Orbit (LEO) at risk. There are fears that collisions between debris could set off a chain reaction, with the result that LEO would become unusable.

Space agencies have begun taking steps to mitigate the problem. A Japanese company launched one such initiative recently. Called Elsa-D, the mission intends to demonstrate a space debris removal system.

MISSION ELSA-D

On March 22, 2021, a Soyuz rocket put 38 payloads into space. Among them was ‘The End-of-Life Services by Astroscale demonstration mission’ (Elsa-D), developed by a Japanese company called Astroscale.

It is the world’s first commercial mission to demonstrate a space debris removal system.

Elsa-D consists of two spacecraft: a 175-kg "servicer" and a 17-kg "client". Client is the fake debris that the ‘servicer’ will have to release, grab, and repeat.

What is the solution?

• The solution involves steps to clean up the mess, mitigate damage, and avoid future debris. There are systems in place to track the debris and avert disasters. Various space organisations have been working on reducing the amount of trash by adopting better designs of rockets and other objects. For example, making rockets reusable could vastly cut down waste.

Hundred million bits
  • Space debris refers to all the human-made objects such as whole and abandoned satellites, pieces of broken satellites, deployed rocket bodies, and other random objects such as tiny flecks of paint from spacecraft and even tools left behind by astronauts during space walks. Most of them orbit Earth and some even beyond it. Some of them have made it to Venus and Mars. Twenty tonnes of them have been found on the Moon, says NASA.
  • According to the European Space Agency, more than 2,400 dead satellites and 100 million bits of debris are already circling Earth. And the debris keeps piling up as satellites have gotten smaller, cheaper, and easier to launch. As of 2020, the United States Space Surveillance Network was tracking more than 14,000 pieces of space debris larger than 10 cm across. It is estimated that there are about 2,00,000 pieces between 1 and 10 cm across.

• The UK’s TechDemoSat-1 (TDS-1), launched in 2014, was designed in such a way that once its mission is over, a system, like a parachute, would drag the satellite to re-enter the atmosphere and burn up. Some satellites at the end of their lifecyle are made to fall out of orbit and burn up in the atmosphere, provided they still have fuel left in them for the descent. Some satellites are sent even farther away from Earth.

• Technologies to remove space junk are also being developed. Cleaning the debris that already exists comes at a high cost, because it will take multiple trips to remove objects from space. Other proposals include the use of a laser to remove debris by changing their course and making them fall towards the atmosphere of Earth and later burn up.

• In December 2019, the European Space Agency awarded the first contract to clean up space debris. ClearSpace-1 is slated to launch in 2025. It aims to remove a 100-kg VEga Secondary Payload Adapter left by the rocket Vega flight VV02 in an 800-km orbit in 2013. A "chaser" will grab the junk with four robotic arms and drag it down to Earth's atmosphere where both will burn up.

What are the risks?

In-orbit risks

The damage can be as small as a dent on a shuttle window to the destruction of an entire satellite. In 1996, a French satellite was hit and damaged by debris from a French rocket that had exploded a decade earlier. Objects in LEO travel at speeds up to 10km/second, fast enough to cause significant damage to satellite, spacecraft, or spacewalking astronauts. The rising number of space debris increases the potential danger to all space vehicles, especially to ones with humans aboard, the International Space Station (ISS), for instance.

• A number of space shuttle windows have been replaced because of damage caused by paint flecks.

• The density of the junk may become so great that it could hinder our ability to use weather satellites, and hence to monitor weather changes.

Debris that re-enters Earth

Space trash is often attracted by Earth’s gravitational pull. It is pulled lower and lower until it finally reaches Earth’s atmosphere. Most objects burn up when they enter Earth’s atmosphere due to the compression of atmospheric gases, but larger objects can reach the Earth intact. But most of them fall into the ocean, simply because Earth is mostly covered by water.

According to NASA website, an average of one catalogued piece of debris has fallen back to Earth each day over the last 50 years. But there have not been any significant damage. People on Earth should avoid contact with the fallen debris, such as rocket parts, because of the possible presence of hazardous chemicals in them.

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Printable version | May 9, 2021 5:18:36 AM | https://www.thehindu.com/children/what-constitutes-space-debris-and-why-they-need-our-attention/article34237578.ece

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