Semi-synchronous orbit is between the distances of 6,000 to 12,000 miles above the Earth. This is mostly used for navigation and communication satellites.
Geo-synchronous orbit is that above 22,000 miles from Earth. This is the best for satellite telecommunication and weather satellites. Items here can remain in orbit for millions of years.
Much of the trash flying around the Earth is a result of normal space missions. Simply satellites that have ceased to be useful, or launch stages of rockets that are shed intentionally. Rubbish has been jettisoned from Space Stations over the years, as astronauts spend extended periods of time in a confined space.
There have also been mistakes and human error which have caused additional pieces of debris, as mentioned, dropping items such as gloves. Over time, collisions between the junk in space has exacerbated the problem, created thousands of smaller individual pieces of debris over time.
Inconceivably, in 2007 China intentionally destroyed a Chinese weather satellite in a test to measure the ability of an anti-satellite missile, creating a considerable amount of junk in it’s wake.
“The greatest risk to space missions comes from non-trackable debris,” said Nicholas Johnson, NASA chief scientist for orbital debris.
Space junk can be deadly in space, even debris as small as a flake of paint can cause enormous damage. This is due to the mind blowing speeds that the particles are travelling at, and also because of the unique design of life-supporting vehicles. To sustain human life it is necessary that individual modules are pressurised to a vacuum. These are particularly vulnerable to damage by piercing.
Despite the huge number of defunct objects in space, the number of collisions is relatively low. This could be due to the physics: all objects in orbit move at the same speed, so any gap between them would remain the same. They wouldn’t get closer together at any point, if they just continued along their path. And that is exactly what they do….most of the time. As soon as an orbiting object fractionally increases its speed, it will climb to a slightly higher orbit. It is at these shifting points that collisions can occur. There is another chance for collision in situations where two satellites orbiting at the same altitude but at different inclinations, cross paths.
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