Ask An Astronomer: Space Debris and Threat They Pose to Satellites, Space Missions – The Weather Channel

Thousands of satellites orbit the Earth to study the planet, support communication and several other purposes. However, once these satellites reach their expiry time, they become space junk or space debris and can turn into a major hazard for other multi-million dollar satellites. Recently, Chinas mission Long March 5B fell into Earth in an uncontrollable mannerthis event once again raised a major alarm related to the space junk floating around in space.

To understand how the space debris gets accumulated and how harmful it is for satellites in space and for the Earth, we spoke to Dr. Abhay Deshpande, a Senior Scientist (Physicist) working for the Government of India. He is also the Honorary Secretary of Khagol Mandal, a non-profit collective of astronomy enthusiasts that organises various sky observation programs, lectures, and study tours.

What is space debris and how does it get accumulated in space?

The first-ever space launch was done in 1957 by the USSRs Sputnik. In the seventies, Europe, Japan, India and China started space launches and as a result, in the past 60 years humans have launched over 6,000 space vehicles to put nearly 10,000 satellites in space. Of these nearly 2,300 are operational while others have stopped working.

Once the satellites become defunct, they drift away from the orbit and slowly start to disintegrate and break into small pieces, which also orbit around the Earth. Some of these parts enter the atmosphere and burn while coming down, while the rest continue to orbit around Earth.

The leftover non-working satellites are around 5,500 or more. They constitute 8,800 tonnes of material in space.This is called space debris and it is a new type of pollution hazard that humanity is facing since the past two decades.

How harmful are these space debris to space assets? What are the chances of collision with other space objects or satellites?

Hubble solar cell impact damage

Space debris is a major challenge as the chances of collision are high. If there is a collision, then the outgoing satellite or space vehicle will be totally damaged. At present the chances of near-by passage of space debris to working satellites is 20,000 approaches per week. This will steadily climb up to 50,000 close-by per week by 2050. At the present rate of accumulation of debris, 1 collision per 5 years with a junk object of size over 10 cm is predicted around 2050. Such collisions will result in total destruction of the satellites or other spaceships.

In February 2009, debris from Russian defunct satellite Kosmos-2251 collided with Iridium-33 satellite, and the functional satellite was broken into more than 2,400 pieces. In May 2013, debris from another Kosmos-1966 devastated Argentinas CubeBug1 and Ecuadors Pegaso satellites. Last September, some debris was about to hit the European satellite Cryosat and it would have resulted in destruction similar to the scenes of the Gravity movie. But the warning system helped and ESA was able to move the Cryosat to safe heights to avoid the collision.

Recently, one of the largest space junk from Chinas mission Long March 5B fell into Earth in an uncontrollable manner. So what are the probabilities of such large space debris impacting the Earth?

On May 5, 2020, China launched LM5B for the testing capability of sending humans in space. On May 12, nearly 18 tonnes of a mass of the empty core came uncontrolled towards Earth making it a probable threat for some parts of the world. Fortunately, the debris fell in the Atlantic Ocean.

This is not the first time for such an impact on Earth by space shuttles. In 1979, American space station SkyLab came falling down and was predicted to fall in the Indian Ocean. Eventually, Skylab fell in the sea but some parts did hit Australia, thus clearly underlining the threat from the skies. In 1991, Soviets Salyut also landed in the sea, and recently in 2018 yet another Chinas space station Tiangong 1 came down in somewhat uncontrolled fashion to eventually make a splash in the South Pacific Ocean.

We see that the potential threat exists and is a reason of concern for us. The more launches we do, the more we have a threat of things coming back to fall on Earth.

How astronomers detect and track debris in space?

Shuttle dragging the dead satellite in the atmosphere to burn.

The space debris is classified based on the size of the particles. There are over 100 million particles of size less than 1 cm. They can cause holes in the solar panels or other instruments and are responsible for minor damages. Particles with a size of more than 1 cm but less than 10 cm are around 1 million in number. They can cause partial to complete damage to the satellite or spacecraft nearby. Particle oversize of 10 cm is around 34,000 in number and are the most dangerous objects. They can cause complete destruction.

The size of the particle also matters depending on which orbit it is seen. If it is close to Earth orbit called Lower Earth Orbit (150 km to 2000 km), then the large particles of 10 cm or more are very dangerous. Space stations are in these orbits only. In contrast, if a particle of 50 cm or more size is in Geo-stationary orbit (far up to 36,000 km) then it will still be considered as a safe object.

We use ground-based telescopes and radio telescopes to track these particles. They are well cataloged and continuously monitored. A large European telescope with a 1-meter diameter mirror is used for observation of debris in Low Earth Orbits. Ultra-High Frequency (UHF) and Very High Frequency (VHF) radars are used as well.

Are there any methods or technologies developed which can efficiently remove the potentially harmful space debris?

Fishing the dead satellites.

There are multiple plans to make sure the space debris issue is mitigated. Let us understand that our atmosphere already is a protection for us. The debris can be carefully pulled into the atmosphere and can be totally burnt off. So, we do have a defence mechanism. One of the options suggested is to send a small spacecraft that can capture the defunct satellites, drag them to the atmosphere in a controlled way and burn them off. Such devices can be Tethers or magnetic locking devices. Other plans are to send similar robotic arm missions but with a fish catching net and capture the debris.

In the near future, are there any missions planned by any space agency to tackle this issue?

Technology demonstration missions are being planned for such experiments. European Space Agency is planning a mission called ClearSpace and it may be launched by 2025 or earlier. Japanese agency JAXA launched an experimental Kounotori Integrated Tither Experiment (KITE) in 2017 but the end part of the mission was not successful. The next mission is being planned.

As satellites continue to be launched at an unprecedented rate, what are the long-term solutions for solving the issue of space debris?

Small space shuttle Tethering the satellite.

One of the most crucial ways to reduce the debris is that when we send a mission, we have to ensure that the spacecraft has an end of life protocol included in it. When the satellite reaches the end of life, it should take up a spiral orbit and enter gradually in the atmosphere and burn off. This will ensure that the debris is not accumulated. But this needs extra fuel and hence the cost will go up.

Another option is to use the fuel and drive off the satellite to further orbit near 3,6000 km and dump it there. Such a dead zone of satellites or so-called parking orbits is the location where they may accumulate. All the devices that can explode should be avoided. Unwanted fuel can be burnt off so that there are no further explosions and the defunct object stays in-tact till long term.

The third and most important aspect is to ensure satellites have multiple technologies integrated and pooled amongst nations. So we can decrease the load in space, to reduce the cost of launch and maintenance.

If we are able to mitigate successfully, we can have a healthy clean space where we can launch vehicles when we want. Else, we will have so much debris by 2050, that each time there is a launch, you will have to wait for hours to get a clear patch.

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This article was produced in collaboration with Khagol Mandal.

This article is a part of an expert interview series. The opinions of the experts does not necessarily represent the official views of The Weather Channel.

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Ask An Astronomer: Space Debris and Threat They Pose to Satellites, Space Missions - The Weather Channel