How much space junk there is up there and what do you need to know about it

Space is not just amazing and clean, it is also full of junk and by junk we mean the remaining of satellites and other space objects that orbit our beautifull planet.
In the list bellow we present you some of the most common questions answered about space junk.

What is orbital debris?
Orbital debris is any human-made object in orbit about the Earth that no longer serves any useful purpose.

What are examples of orbital debris?
Derelict spacecraft and upper stages of launch vehicles, carriers for multiple payloads, debris intentionally released during spacecraft separation from its launch vehicle or during mission operations, debris created as a result of spacecraft or upper stage explosions or collisions, solid rocket motor effluents, and tiny flecks of paint released by thermal stress or small particle impacts.

How much orbital debris is currently in Earth orbit?
More than 23,000 orbital debris larger than 10 cm are known to exist. The estimated population of particles between 1 and 10 cm in diameter is approximately 500,000. The number of particles larger than 1 mm exceeds 100 million. As of January 1, 2020, the amount of material orbiting the Earth exceeded 8,000 metric tons.

How is the number of orbital debris determined?
Large orbital debris (> 10 cm) is tracked routinely by the U.S. Space Surveillance Network. Objects as small as 3 mm can be detected by ground-based radars, providing a basis for a statistical estimate of their numbers. Assessments of the population of orbital debris smaller than 1 mm can be made by examining impact features on the surfaces of returned spacecraft, although this has been limited to spacecraft operating in altitudes below 600 km.

What is the principal source of large orbital debris?
Satellite explosions and collisions. Prior to 2007, the principal source of debris was from explosions of launch vehicle upper stages and spacecraft. The intentional destruction of the Fengyun-1C weather satellite by China in 2007 and the accidental collision of the American communications satellite, Iridium-33, and the retired Russian spacecraft, Cosmos-2251, in 2009 greatly increased the number of large debris in orbit and now represent one-third of all cataloged orbital debris.

How fast is orbital debris traveling?
In low Earth orbit (below 2,000 km), orbital debris circles the Earth at speeds of about 7 to 8 km/s. However, the average impact speed of orbital debris with another space object is approximately 10 km/s, and can be up to about 15 km/s, which is more than 10 times the speed of a bullet. Consequently, collisions with even a small piece of debris will involve considerable energy.

Does the International Space Station have to dodge orbital debris?
The U.S. Space Surveillance Network regularly examines the trajectories of orbital debris to identify possible close encounters. If another object is projected to come within a few kilometers of the International Space Station (ISS), the ISS will normally maneuver away from the object if the chance of a collision exceeds 1 in 10,000. This occurs infrequently, about once a year on average.

How is the International Space Station protected against orbital debris?
The ISS is the most heavily shielded spacecraft ever flown. Critical components, e.g., habitable compartments and high pressure tanks, will normally be able to withstand the impact of debris as large as 1 cm in diameter. The risk of a critical ISS component being struck by debris 1-10 cm in diameter is slight and ways to reduce this risk are being investigated.

How did the Mir space station fare during its 15-year stay in Earth orbit?
Photographs of Mir’s exterior show large numbers of impacts from small orbital debris and meteoroids. The most significant damage was to the large, fragile solar arrays that could not be protected from small particles. Orbital debris caused no loss of mission or capability on Mir.

Do the low altitude, commercial communication satellite networks pose special debris issues?
Systems such as Iridium, Orbcomm, and Globalstar do not represent unique debris problems. In fact, many of the systems are being deployed in ways designed to minimize orbital debris generation. Often, upper stages and spacecraft are placed in lower altitude orbits after their missions have been completed to accelerate their fall back to Earth.

How long will orbital debris remain in Earth orbit?
The higher the altitude, the longer the orbital debris will typically remain in Earth orbit. Debris left in orbits below 600 km normally fall back to Earth within several years. At altitudes of 800 km, the time for orbital decay is often measured in centuries. Above 1,000 km, orbital debris will normally continue circling the Earth for a thousand years or more.

Source: N.A.S.A.

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