at because the satellites orbit above the equator, dishes in the northern hemisphere always face south. The farther north a user's receiver dish is located, the lower it has to be ori- ented. Where I live in Vermont, the satellite dishes are practically lying on the ground-they almost look as of they are receiving signals from the depths of the mountains instead of a satellite orbiting 23,000 miles above the Earth. Low/Medium Earth Orbit Satellites (LEO/MEO) In addition to the geosynchronous satellite arrays, there are a variety of lower orbit constellations deployed known as low and medium Earth Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Access Technologies Access Technologies orbit satellites (LEO/MEO). Unlike the geosynchronous satellites, these orbit at lower altitudes-400-600 miles, far lower than the 23,000-mile altitude of the typical GEO bird. As a result of their lower altitude, the transit delay between an Earth station and a LEO satellite is virtually nonexistent. However, another problem exists with low Earth orbit tech- nology. Because the satellites orbit pole-to-pole, they do not appear to be stationary, which means that if they are to provide uninterrupted service they must be able to hand off a transmission from one satellite to another before the first bird disappears below the horizon. This has resulted in the development of sophisticated satellite-based technology that emulates the functionality of a cellular telephone network. The dif- ference is that in this case, the user does not appear to move; the cell does! Iridium Perhaps the best-known example of LEOs technology is Motorola's ill- fated Iridium deployment. Comprising 66 satellites in a polar array, Iridium was designed to provide voice service to any user, anywhere on the face of the Earth. The satellites would provide global coverage and would hand off call