The LEO Environment
The LEO environment refers to a low earth orbit, which lies beneath an altitude of 1200miles. However since the rate of decay in the orbit is high, the accepted definition of the LEO is an area that lies between 99and 1200 miles above the surface of the earth. All recorded human spaceflights that took place in the LEO were suborbital that is, occurred below the orbit of the earth. Space stations and most of the satellites to date are located in the Low Earth Orbit. The LEO environment has specific characteristics that differentiate it from all the other regions in space. The Low Earth Orbit region has been a very important discovery in astronomy since it has been used for several things but most notably, it has revolutionized the telecommunications sector.
The unique traits that it possesses are due to its location. When objects get into the LEO, they face atmospheric drag. This effect is often in the form of gases located in the exosphere or the thermosphere. In the case of the exosphere, it occurs about 500kilometres above the LEO. The thermosphere occurs between 80 and 500 kilometers above the LEO. Specifically, the LEO lies between the earth’s atmosphere and a radiation belt called the Van Allen belt. There exists a subset of the LEO called the Equatorial Low Earth Orbit (ELEO). The ELEO has a low leaning to the equator, which facilitates fast revisit times. In addition to this, the ELEO has the lowest recorded delta-v requirement while compared to the rest of the existing orbits. With regard to the level of inclination, orbits with high angles of inclination are referred to as polar orbits. Above the LEO is another region, the Medium Earth Orbit (MEO), which is at times, called the Intermediate Circular Orbit (ICO) (Ridpath 59).
It is called the ICO because of its shape and location in space. Above the ICO is the Geostationary Earth Orbit (GEO). The LEO is distinguishable from the ICO and the GEO because the latter has powerful radiation and accumulates a lot of charge. This characteristic causes a failure of electronic devices when they are exposed to these regions. However, in the LEO, the devices are able to function normally and this difference has enabled the astronomers to distinguish these regions in the atmosphere. Another distinguishing characteristic is that people and objects in this region encounter buoyancy or weightlessness. It is common knowledge that gravity causes the earths pull, but in this region, the effect of gravity is cancelled due to the increased orbital speed that increases the centrifugal acceleration in the LEO (Maran, 89).
Using the characteristics that the astronomers have acquired from research, they have been able to construct man made LEO’s in the atmosphere. A good example of a manmade LEO is the International Space Station. It is located between 199 and 249 miles above the surface of the earth. The LEO has also been very important in communication. Most of the artificial satellites are located the LEO and they complete a revolution in about one and a half hours. Several satellites used for communication need geostationary orbits, which move at the same speed as the earth. However, it was discovered that placing a satellite into the LEO needs very little energy and the satellite needs amplifiers of lower power to transmit the information. It was concluded that it is more economical to place the satellites in the LEO as opposed to the other regions above it and this is why majority of the communication satellites are located here (Martin, Anderson and Bartamian, 34)
. Nevertheless, since the LEO is not geostationary, a constellation of satellites has to be installed to ensure that the transmission process is effective. Observation satellites have also been able to make use of the LEO. At an altitude of 500 miles near the level of polar inclination, the observation satellites are able to function optimally. ENVISAT is one of the satellites, which incorporates this technology in its functioning. The amount of space debris located in the LEO region is fast becoming a worrisome matter. This growing concern is because collisions that occur in this region are dangerous and may damage the artificial satellites, which are very costly. Several astronomers are creating awareness about the effects on the matter in a bid to avert the effects associated with them (Manuel, Martin and Rosa, 56).
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Martin, D. H, Anderson, P. R. and Bartamian, L. Communication Satellites. El Segundo, Calif: Aerospace Press, 2007. Print.