|
|
Low Earth Orbit (LEO)
People worry about the items now in low earth orbit. Not all of these are satellites, there are pieces of metal from old rockets, broken satellites. At 17,000 mph, even a small bolt can hit a space craft with a big impact. Most artificial satellites are placed in LEO, making one revolution in about 90 minutes. The primary exception are communication satellites that require geostationary orbit. However, it requires less energy to place a satellite into a LEO and the satellite needs less powerful transmitters for data transfer, so LEO is still used for many communication applications. Because these orbits are not geostationary, a network of satellites is required to provide continuous coverage. Lower orbits also aid remote sensing satellites because of the added detail that can be gained The low Earth orbit for communications has more in common with terrestrial Land Mobile Radio communications networks than conventional Geo-stationary satellite communications systems. In a terrestrial mobile system the user moves successively through a series of cells. In a low Earth orbit communication system the satellite footprint, acting like a cell, moves through the users. |
When
a satellite circles close to Earth it's in Low Earth Orbit. These Satellites
are 200 - 500 miles. Because they orbit so close to Earth, they must travel
fast so gravity won't pull them back into the atmosphere. Satellites in LEO
travel along at 17,000 miles per hour.