 that satellite is in, but this is one application that merges the ISP and satellite industries. Other emerging applications of satellites include telemedicine, distance learning, remote imaging, and weather information. Satellites have seen a number of innovations and are facing yet more in the future. The most significant change in the coming years is that satellites will increasingly deliver information directly to the consumer rather than to a commer- cial data hub. This might mean that aerospace corporations become major compet- itors of traditional telecom carriers. Another key innovation is phased-array antennas. A phased-array antenna consists of multiple transmitting elements, arranged in a fixed geometric array. These small, flat antennas are steered electronically, and they provide great agility and fast tracking. Phased-array antennas, as well as other new designs in antennas, are discussed in Chapter 13. Key challenges for satellites today are related to power and mobile services. Because the small antennas now used in portable transceivers intercept only a tiny fraction of the satellite signal, satellites must have a lot of power and sensi- tivity; a typical solar array on a GEO satellite increased in power from 2kW to more than 10kW in just several years. Another innovation involves moving fur- ther up the frequency spectrum, to make use of extremely high frequencies (EHF). The highest-frequency satellite systems today use wavelengths comparable to the Chapter 2 Traditional Transmission Media size of a raindrop. Consequently, a raindrop can act as a lens, bending the waves and distorting the signals. But these ill effects can be mitigated by using error correction techniques, by applying more power when necessary, or by using more ground terminals SO data can follow diverse paths. When wavelengths are smaller than a millimeter, there are yet more obstacles. Infrared and optical beams are easily absorbed in the atmosphere. So, in the near future, they may very well be restricted to use within buildi