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A Litter Metropolis in the Sky

Space Debris: What is it?

It is simply everything from decommissioned satellites to screws to jettisoned parts of rockets. Ever since 4th October 1957, when Sputink 1, our first ever artificial satellite, went into orbit around Earth, the skies have been filling with ever more increasing amounts of litter, some of which travel at speeds over 22,300 mph.

Then, as all this debris has been building up, it has been crashing into other satellites and making more and more debris. These events have therefore increasing over the last few decades, with this being made worse by anti-satellite missile launches from China (2007 and 2009 tests) and India, making another 400 fragments of satellite, ready to hit anything, from a GPS satellites to the ISS [1].

Indeed, the ISS has been feeling the brunt of this new phenomenon, with the threat so prominent that a sophisticated detection system to label space debris has been made, labelling them as either yellow (1 in 100,000 chance of impact) or red (1 in 10,000 chance impact), but these warnings aren’t like at a football match; they help keep the crew alive. Indeed, if they did think a piece of space debris to be a significant threat, then they would move the whole ISS in a Debris Avoidance Manoeuvre, or DAM, to get it out of the way [2].

However, this is not ideal, so is not always carried out, leading to the odd chip in the window (as seen in the image below) and even the odd air leak!

Presently, there is more than 8,800 tonnes of man-made objects in orbit around Earth, with 128 million objects from 1mm to 1cm in size (still being deadly if travelling at 22,300 mph) [3].

And then, there’s the problem of not only having space debris crashing into other satellites that were otherwise functioning perfectly, but some of it (very rarely it has to be said) falling down to Earth, uncontrolled. It was 20 tonnes of Chinese rocket that reentered the Earth’s atmosphere at 4pm on 11th May 2020, as part of China’s “Long March 5B”; China’s largest and most recent rocket, which created the 4th largest piece of debris to reenter Earth [4]

Many satellites do get de-orbited, falling into a place nicknamed the “Spacecraft Cemetery”, also called Point Nemo, being the furthest place from people anywhere on Earth, located in the south of the Pacific Ocean. However, this is not the fate for all satellites, with a “Graveyard Orbit” being made 22,400 miles above Earth, around 200 miles from the outer active satellites [5], but, is it right to be making a graveyard in space, when we want to be making manned missions to Mars and the Moon in the near future?

Impact chip on ISS window

Impact chip on ISS window. Credit: ESA, NASA, Tim Peake

Orbital Surveillance

The immediate problem now is that, once you’ve sent your shining new satellite worth in the millions or billions of pounds, it then is destroyed by some debris someone else forgot to clean up. So, the first frontier in the fight against collisions is to track these millions of pieces of debris in orbit, preventing such collisions from ever happening.

Groups like the American and Russian military are keeping an eye on orbital space debris, warning people of impending collisions, using optical telescopes like the USA’s Space Surveillance Telescope (which will be operational again in 2022) [6], with objects as small as 10cm visible to these telescopes [7] (you can see all the data of space debris orbiting the Earth on this website, which shows a visualisation of whereаbouts all the known pieces of debris out there at the moment).

Adapting Design

Another option is to reduce the amount of debris out there, which is what various space agencies have done, with Russia, China, Japan, France and ESA outlining how to reduce the emission of debris [7], with everything from end of life disposal into the “Graveyard Orbit”; to testing of satellites so that, if something were to fall into Earth, it wouldn’t cause harm to people; to preventative technologies to stop shedding of fuel, discharging of batteries and explosions in space, reducing the amount of debris created once more (all found in the very detailed code of conduct here) [8].

One extreme example of this is seen in Elon Musk’s reusable landing rocket (which landed on a floating space port), first launched from Cape Canaveral in 2016, heading for the ISS, before landing on a floating barge in the Atlantic Ocean (seen on this clip by the BBC). It produces little space debris and can reduce costs by being reused [9] (like in NASA’s Space Shuttle Program, although hopefully with less safety issues).

Falcon 9 1st Stage Landing

Falcon 9 1st Stage Landing. Credit: SpaceX

Active Removal

Now, technology is being implemented in the form of Active Debris Removal (ADR), which could dramatically decrease the amount of debris in the atmosphere (shown in the image below), by taking out all the high mass, high collision probability and high altitude space debris, reducing impact of space debris on missions that are active.

They have even identified areas where debris will accumulate, being: “100km and 80º inclination, 800km and 98º inclination, and 850km and 71º inclination”, being places where the ADR projects are likely to target first, having the greatest impact on the amount of debris in orbit around Earth [10].

There are many ways this has been theorised to work, including ESA’s e.DeOrbit idea, which has many different methods proposed for the capture of debris, including everything from harpoons to nets and even robotic arms.

Solar sails to push debris down, swinging satellites capturing debris by its shear momentum, and spacecraft on the back of planes are also all proposals to remove debris from Earth orbit [11], but which one will be viable and will bring us out of the mess we’ve put ourselves in?

Predictions with and without ADR by 2209

Predictions with and without ADR by 2209. Credit: ESA, CC BY-SA 3.0 IGO

'World’s First Debris Removal Mission'


The very first ADR mission contract was signed 2 days ago (26/11/20), with ESA signing up to an €86 million contract with ClearSpace SA: a Swiss start-up, with a mission in 2025 called ClearSpace-1, to be launched.

It is planned to capture the Vespa (Vega Secondary Payload Adapter), having been put in a gradual disposal orbit, and close to the size of a small satellite, at 112kg in mass [12].

However, apart from being different in being the first ADR mission, it’s also different in that ESA haven’t decided how the mission is going to work, hoping to create a more commercial environment, to then bring about lower cost ADR missions, so as to have a lot more like this one in the future [13].

The proposed method of capture is to rendezvous with the payload, before using 4 robotic arms to capture it, and drag it down to its fate, in Earth’s atmosphere, which will burn up the debris [14], as seen in phenomena like meteor showers and fireballs.

Whatever method of removal is used in the future, one thing is for sure: it is necessary, since, if we don’t, it will just build up and build up, until it becomes impossible to have satellites in Earth orbit, instead having a wall, rather like in WALL-E.

Main propellant tank of 2nd stage of Delta 2 Landed Texas 1997

Main propellant tank of 2nd stage of Delta 2 Landed Texas 1997. Credit: NASA ODPO

By George Abraham, ADAS member

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Click here to see the current state of our space debris problem



  1. "Space junk is a huge problem–and it's only getting bigger". National Geographic. Archived from the original on 28th November 2020.

  2. "How Much of a Threat is Space Debris to the ISS?". Forbes. Archived from the original on 28th November 2020.

  3. "Space Debris by the Numbers". ESA. Archived from the original on 28th November 2020.

  4. "A Huge Hunk of Space Debris Fell to Earth". Smithsonian Magazine. Archived from the original on 28th November 2020.

  5. "Where do Old Satellites Go When they Die?". NASA Space Place. Archived from the original on 28th November 2020.

  6. "U.S. Space Force is deploying surveillance telescope in Australia". Space News. Archived from the original on 28th November 2020.

  7. "Space Junk: Tracking & Removing Orbital Debris". Archived from the original on 28th November 2020.

  8. "Mitigating space debris generation". ESA. Archived from the original on 28th November 2020.

  9. "SpaceX lands rocket on ocean barge after take-off". BBC. Archived from the original on 28th November 2020.

  10. "Active debris removal". ESA. Archived from the original on 28th November 2020.

  11. "Space Junk Clean Up: 7 Wild Ways to Destroy Orbital Debris". Archived from the original on 28th November 2020.

  12. "Nº 26-2020: Call for Media: ESA and ClearSpace SA sign contract for world's first debris removal mission". ESA. Archived from the original on 28th November 2020.

  13. "Spacewatch: ESA awards first junk clean-up contract". The Guardian. Archived from the original on 28th November 2020.

  14. "ClearSpace-1 set to clean up space debris". The Engineer. Archived from the original on 28th November 2020.

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