Kessler Syndrome

The Kessler syndrome (or Kessler effect, is a cascade effect. It was suggested by NASA scientist Donald J. Kessler in 1978. The scenario occurs when the space pollution is high enough for collisions between objects to occur.
There is a satellite in orbit that is large and inactive, making it count as space debris, but it is in an orbit with a large amount of space debris. Two known objects get within 200m of it every year. This could cause a lot of space debris, inducing a domino effect with more collisions.
Avoiding Kessler syndrome.
Satellite manufacturers must demonstrate that their satellite can safely destroy itself or boost itself into a higher or lower orbit, known as a graveyard orbit, to avoid keeping unused satellites in common orbits for other satellites.