Satellites orbiting the earth are used to receive and retransmit signals for telephone, television, radio, and data communication. The basic relay device in satellites, the transponder, has seen tremendous increases in efficiency thanks to advances in compression technology. A communications satellite system comprises the satellites and the ground stations for transmitting and receiving the signals. Direct broadcasting satellites, which are geostationary, transmit radio and TV services that consumers can receive through a cable redistribution network or a personal domestic disc antenna. Recently a digital satellite radio system was inaugurated using satellites over Africa, the Middle East, Asia, and Latin America. Signals from these satellites—including distance education programs that are planned—will be able to be received directly on special portable radio receivers.

Communications satellites resources (external links)

• White Paper on SchoolWeb
  
• The Use Of Satellite Technology In Distance Education For Delivering Instruction
  
• Handbook for Satellite Downlink Operators and Meeting Facilitators
  
• Facts, figures and stories on using satellites
  
• Mike Jensen, A Guide to Improving Internet Access in Africa with Wireless Technologies.
  
  • "Geostationary Satellites and Satellite Equipment and Services." Available at: http://www.idrc.ca/acacia/studies/ir-jens4.htm

  • "Geostationary Satellite Operators in Africa and Non-Geostationary Orbit (NGSO) Satellites." Available at: http://www.idrc.ca/acacia/studies/ir-jens5.htm Permission to link granted.

• Telemedicine and health care delivery via INMARSAT. Available at: http://www.inmarsat.org (Click on "Telemedicine information). Permission to link granted.

• University of Wisconsin-Extension. Satellite. Distance Education Clearinghouse. Available at: http://www.uwex.edu/disted/satellite/index.html/