Satellites

COMMUNICATIONS GUIDE

Satellites

Technological Advances Provide Faster and Cheaper Transmissions

ore than 150 communications satellites are orbiting the globe, providing rapid and cost-effective transmission of data, voice and video. They facilitate everything from television transmissions and telephone calls to computer networking, videoconferencing and training. And they are no longer reserved exclusively for military, intelligence or space operations.

Federal agencies are using satellites for general administrative functions such as software distribution or inventory updates. Receiving dishes can be seen on top of many government buildings these days, mainly because technological advances by companies such as GTE, Harris, Hughes and Lockheed Martin have brought satellite technology within financial reach.

Satellites can be significantly more cost-effective than land-based coaxial cables or fiber-optic networks. A single satellite's coverage area-called footprint-covers up to one-third of the earth. And unlike wired telephony service, satellite costs are not affected by distance.

Satellite communications are more robust than ever. Some of the newer satellites contain as many as 90 transponders, which are electronic devices used to transmit and receive radio signals at different frequencies. NASA is working with the Air Force and the Defense Department's Advanced Research Projects Agency to develop a "phased array" satellite antenna system capable of simultaneously directing multiple signals to multiple sites. The K-Band Multibeam system will deliver 500 percent more power for a fraction of the price of current satellite systems.

In addition to becoming more powerful, receivers are getting smaller. Twenty-inch dishes are becoming commonplace, while companies are even working on briefcase-size terminals. Hughes' DirecPC high-speed satellite distribution system is the first service to feature a satellite receiver in the form of a PC card, enabling users to capture broadcasts and write them directly to hard drives. The kit includes a 24-inch VSAT (very small aperture) dish that connects via cable to the card. The system can transmit large Internet files in seconds.

Smaller receivers are ideal for remote applications, where other types of communications are expensive and logistically difficult because of rugged or hostile territory. Troops in Bosnia depend on 45 tiny satellite receivers for their digital direct broadcast systems. The technology provides an inexpensive way for them to transmit high-bandwidth graphical data files. A dedicated satellite is used for on-line ordering of pharmaceutical and communications products via the government's Federal Acquisition Network.