Earth’s Space Junk
NASA estimates that more than 100 million man-made objects the size of a grain of salt are orbiting the planet. About 500,000 objects that are roughly the size of a marble are also believed to be out there, as well as 23,000 objects the size of a softball or larger.
The amount of such fragments has expanded exponentially since the dawn of space exploration in the early 1960s. It has primarily resulted from discarded rocket parts and satellites, as well as from smash-ups between chunks space junk over the years — much of the debris is made up of bits of other debris. This phenomenon is known as the Kessler Syndrome, named for NASA scientist Donald Kessler, who described the effect in 1978.
Concern about space junk goes back to the beginning of the satellite era, but the number of objects in orbit is rising so rapidly that researchers are investigating new ways of attacking the problem. Several teams are trying to improve methods for assessing what is in orbit, so that satellite operators can work more efficiently in ever-more-crowded space. Some researchers are now starting to compile a massive data set that includes the best possible information on where everything is in orbit. Others are developing taxonomies of space junk — working out how to measure properties such as the shape and size of an object, so that satellite operators know how much to worry about what’s coming their way. And several investigators are identifying special orbits that satellites could be moved into after they finish their missions so they burn up in the atmosphere quickly, helping to clean up space.
In theory, satellite operators should have plenty of room for all these missions to fly safely without ever nearing another object. So some scientists are tackling the problem of space junk by trying to understand where all the debris is to a high degree of precision. That would alleviate the need for many unnecessary manoeuvres that today are used to avoid potential collisions.