Satellite Decays per Year
The number of satellites that decay per year has been increasing since 1957
When two satellites collide, they can break apart into hundreds of pieces. These pieces can then collide with other satellites and create a chain reaction.
Space is a rough environment. Satellites are constantly being hit by micrometeorites and other debris. These impacts can cause satellites to break apart into smaller pieces.
Launches often leave behind the upper stage of the rocket in orbit. These rocket bodies can stay in orbit for decades before they decay.
Most satellites are not designed to be deorbited. When they reach the end of their life, they are left in orbit and become space debris.