What is Orbital debris AKA space junk?

Orbital debris (duh BREE) is “junk” that is circling Earth. It is any human-made object in orbit around the Earth that no longer serves a useful function, Such debris includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris, and fragmentation debris. Humans have been launching objects into space for more than 50 years. Most of those objects have fallen back to Earth. A piece of debris falls back to Earth about once a day. These objects either land or burn up in the atmosphere. Most objects that return to Earth end up in water, since it makes up 70% of Earth’s surface. But many of the objects sent into space are still in orbit around Earth.

Even tiny paint flecks can damage spacecraft when traveling at these velocities. A number of space shuttle windows were replaced because of damage caused by material that was analyzed and shown to be paint flecks. In fact, millimetersized orbital debris represents the highest mission -ending risk to most robotic spacecraft operating in low Earth orbit.

Most of that debris sits within 1,250 miles of Earth’s surface in what is known as low Earth orbit, home to lots of satellites, such as NASA’s Earth Observing System fleet and the International Space Station. And while space is big—so even 23,000 fragments tend to be far from each other—even the tiniest bits of man-made flotsam can be problematic for active earth orbiters because of their breakneck speeds.

Who are they and what are they doing for space?