ngs; however, there have been some new developments in virtual fiber, which is discussed in Chapter 15. HALES A slightly different orbit is being introduced: high-altitude, long-endurance (HALE) satel- lites, which the ITU also calls high-altitude platform stations (HAPS). HALES are in extremely low orbit, actually circling a city or metro area. They are about 11 miles (17.8 km) over- head, and they operate at about 47GHz, although the ITU has also designated other bands of operation, including 3G bands. The main applications are Internet access, resource monitoring, and data networking in metropolitan areas. In essence, they are air- craft that hover over a city area, providing network capacity for metropolitan area net- working. Some may be dirigibles, and others may have wings and fly like conventional aircraft. The key advantage associated with HALES is a very moderate launch cost compared to the cost associated with traditional satellites. By applying what we are learning to do with phased-array antennas (discussed in Chapter 13) to HALEs, we can provide a wide capacity: Some 3,500 beams could enable mobile two-way communications and video distribution in an area about 300 miles (about 500 km) across. Advantages and Disadvantages of Satellite The advantages of satellite include the following: Access to remote areas Coverage of large geographical areas Insensitivity to topology Distance-insensitive costs High bandwidth The disadvantages of satellite include the following: High initial cost Propagation delay with GEO systems Fiber Optics Environmental interference problems Licensing requirements Regulatory constraints in some regions Danger posed by space debris, solar flare activity, and meteor showers Fiber Optics In the late 1950s and early 1960s, a number of people were working in the realm of fiber optics simultaneously. Charles Kao, who was a scientist with ITT, is often acknowledged as being one of the fathers of fiber optics. Kao theorized that if we could develop a procedure for manufacturing ultrapur