Mankind launched the first artificial object into orbit October 4, 1957. Sputnik 1 continued to orbit the Earth for 3 months, before it reentered the atmosphere and was destroyed January 4, 1958.
Since then, 1000’s of satellites have been launched into space, occupying a variety of orbits. The two most common places to put satellites are Low Earth Orbit (LEO) or Geosynchronous Orbit (GEO).
Low Earth spans an altitude range of about 160km to 2000km, and the majority of satellites are in this range. The International Space Station is here, as are many communications satellites, spy satellites, weather satellites, and the Hubble Space telescope. Low Earth orbit takes less energy to get to than any other orbit, though objects in LEO can be affected by atmospheric drag.
Geostationary Orbit is 32,000 km up, and is exclusively the domain of communications satellites. An object in a geosynchronous orbit will remain above the same spot on the earth below.
GPS satellites occupy a special case, midway between LEO and GEO.
Along with all these satellites has come trash. This orbital waste comes from a variety of sources, and includes dead satellites, nuts, bolts, flecks of paint, a glove from a spacesuit(!) and over 100 bags of garbage ejected from the Russian space station, Mir. The majority of the debris, however comes from a few rockets that exploded, and from ASAT (Anti SATellite) tests.
In 2007, the Chinese conducted an ASAT test against a defunct communications satellite. The explosion created well over a million pieces of debris, including over 3500 pieces golf-ball sized or larger, which could cause serious damage to a satellite or manned spacecraft.
It is estimated that there are tens of millions of fragments smaller than 1cm, which cannot be tracked. Another 500,000 pieces between 1 and 10 cm in size, and 19,000 over 10cm across. Total mass of all of these objects is estimated to be on the order of 5500 tons.
In 1983, on it’s first mission, the space shuttle Challenger was hit by a fleck of paint on the forward window, which left a pit 1 mm across, and looked very similar to a rock strike on your windshield. That fleck was one of the millions of pieces too small to be tracked.
Even in space, mankind can’t help from dirtying the pool. It gets worse, however, There is so much debris in space, especially in LEO, that scientists are afraid of a domino effect. As satellites get damaged, they shed debris, which goes on to shred other satellites, and the whole thing quickly gets out of control. This is called the Kessler Syndrome, and many scientists fear that in the more commonly used bands around earth, we have already past the threshold for the amount of debris required to initiate a cascade of devastation.
When faced with information like this, the first question we ask is “Can anything be done?” “How can we clean up our mess?” After all, LEO is where our most valuable and useful satellites are, the weather satellites, earth-monitoring satellites, space telescopes, photo satellites and many communications satellites are found. Our lives would change if these were destroyed.
There have been a variety of solutions proposed. Already, objects like the International Space are armored to protect them from the smallest of the debris objects, and even something as large as the station can be moved to avoid an incoming threat.
Beyond immediate mitigation, there are ideas to clean up orbital space. The so-called “laser broom” would sweep space in front of the space station, vaporizing debris so as to pose no threat to the station. Another concept is to use vast collectors coated with aerogel to capture debris for disposal.
If the cleanups fail, and a Kessler Syndrome transpires, we may lose access to space, possibly for a long time. From the standpoint of someone interested in a green earth, we would lose the satellites that monitor the ozone layer, track storms, measure global temperatures, track polar ice, and a whole host of other functions that have come to be of critical importance in the struggle to save our environment from ourselves.