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spread. Figure  2.1 shows the build up over time of the debris around Earth and how it has escalated in recent years. In 1980 the problem was hardly apparent, and even by 1985 it seemed almost trivial, but today it is clearly a larger and growing issue.
    There are a number of other important aspects to note with regard to the orbits that are of importance. One aspect is that there are different disposal concepts that apply to these three different orbits. One logical disposal mode is to fire jets so that a satellite in LEO will simply de-orbit and burn up on its descent or splash down into the ocean. For geosynchronous satellites the disposal method is to push the spacecraft to a graveyard orbit that is higher than the geo orbit. When thus positioned there, these satellites can stay in super synchronous orbit for millions of years.
    The greatest challenge is presented by the MEOs in terms of the disposal of satellites at end of life. Only a small amount of increment fuel is required to de-orbit a LEO satellite or to push a GEO satellite into a higher graveyard orbit. The disposal of MEO satellites is a problem in that a 40 % greater amount of fuel—beyond that used for orbital positioning—is needed to de-orbit a spacecraft launched into this orbit. This constitutes a very large economic penalty in terms of launch costs and increasing the size of propellant fuel tanks. Other options might be explored to move MEO satellites at end of life into some type of "graveyard or parking orbit", but this would not be an easy or permanent solution because the Sun, Earth and Moon would impact this type of orbit and thus it would not be stable.
    Actually the problem and complexity of this final disposal issue only increases when probed further. Satellites can lose their ability to be commanded and thus be stranded in their orbits. Elements of the launch such as the upper stage rocket, fairings that served to protect the satellite from the atmosphere during launch and other extraneous parts can be launched and stranded in orbit with no mechanism to de-orbit them except for gravitational pull and atmospheric drag. Some satellite operators have claimed that they were requested not to de-orbit their failed satellites from operators of defense-related satellites because of possible collision with clandestine satellites uses for surveillance.
    If the launch of a spacecraft is into LEO, these elements will eventually degrade, but this is not the case with MEO or GEO orbit. And, of course, not all satellites are launched into LEO, MEO or GEO orbit. Some satellites are launched into highly elliptical orbits such as the so-called “Molniya” orbit, named after the Russian satellite with this name. Or satellites can be launched into a somewhat similar highly elliptical “Loopus” orbit. There are also various other orbits such as the Quasi-Zenith or Figure 8 orbit (i.e., a geo orbit inclined 45 degrees), super-synchronous orbits and even unintended orbits. These last can result from a launch failure when the rocket fires too long or not enough, and thus the rocket is put on the wrong path.
    Once a satellite or rocket motor becomes stranded in orbit, it can become a source of additional debris. Any of these stranded or even actively controlled space objects can be hit by another piece of debris at high speed and generate other debris. A fuel tank or a battery might explode and create additional elements of debris. The recommended procedure of venting fuel tanks for end of life satellites is considered an important procedure now widely practiced to help minimize space debris.
    The uneven distribution of orbital debris creates problems with regard to those who perceive this as a serious issue and those willing to support in an active way the cleaning up of the mounting amounts of space junk. Those who operate satellites in GEO orbit are inclined to respond to concerns about rising debris by saying this is largely a LEO and polar orbit problem