Satellite+communication

=__**Satellite Communication**__=

toc =__**Definition:**__= (britannica.com, 2011)
 * satellite communication ****,** in telecommunications, the use of artificial satellites to provide communication links between various points on Earth. Satellite communications play a vital role in the global telecommunications system. Approximately 2,000 artificial satellites orbiting Earth relay analog and digital signals carrying voice, video, and data to and from one or many locations worldwide.

=__**Overview:**__= Satellite communication has two main components: the ground segment, which consists of fixed or mobile transmission, reception, and ancillary equipment, and the space segment, which primarily is the satellite itself. A typical satellite link involves the transmission or uplinking of a signal from an Earth station to a satellite. The satellite then receives and amplifies the signal and retransmits it back to Earth, where it is received and reamplified by Earth stations and terminals. Satellite receivers on the ground include direct-to-home (DTH) satellite equipment, mobile reception equipment in aircraft, satellite telephones, and handheld devices. (britannica.com, 2011)

=__**The billion dollar technology, the start of a new generation:**__= In fall of 1945 an RAF electronics officer and member of the British Interplanetary Society, Arthur C. Clarke, wrote a short article in //Wireless World// that described the use of manned satellites in 24-hour orbits high above the world's land masses to distribute television programs. His article apparently had little lasting effect in spite of Clarke's repeating the story in his 1951/52 //The Exploration of Space//. Perhaps the first person to carefully evaluate the various technical options in satellite communications //and// evaluate the financial prospects was John R. Pierce of AT&T's Bell Telephone Laboratories who, in a 1954 speech and 1955 article, elaborated the utility of a communications "mirror" in space, a medium-orbit "repeater" and a 24-hour-orbit "repeater." In comparing the communications capacity of a satellite, which he estimated at 1,000 simultaneous telephone calls, and the communications capacity of the first trans-atlantic telephone cable (TAT-1), which could carry 36 simultaneous telephone calls at a cost of 30-50 million dollars, Pierce wondered if a satellite would be worth a billion dollars.

After the 1957 launch of Sputnik I, many considered the benefits, profits, and prestige associated with satellite communications. Because of Congressional fears of "duplication," NASA confined itself to experiments with "mirrors" or "passive" communications satellites (ECHO), while the Department of Defense was responsible for "repeater" or "active" satellites which amplify the received signal at the satellite--providing much higher quality communications. In 1960 AT&T filed with the Federal Communications Commission (FCC) for permission to launch an experimental communications satellite with a view to rapidly implementing an operational system. The U.S. government reacted with surprise-- there was no policy in place to help execute the many decisions related to the AT&T proposal. By the middle of 1961, NASA had awarded a competitive contract to RCA to build a medium-orbit (4,000 miles high) active communication satellite (RELAY); AT&T was building its own medium-orbit satellite (TELSTAR) which NASA would launch on a cost-reimbursable basis; and NASA had awarded a sole- source contract to Hughes Aircraft Company to build a 24-hour (20,000 mile high) satellite (SYNCOM). The military program, ADVENT, was cancelled a year later due to complexity of the spacecraft, delay in launcher availability, and cost over-runs.

By 1964, two TELSTARs, two RELAYs, and two SYNCOMs had operated successfully in space. This timing was fortunate because the Communications Satellite Corporation (COMSAT), formed as a result of the Communications Satellite Act of 1962, was in the process of contracting for their first satellite. COMSAT's initial capitalization of 200 million dollars was considered sufficient to build a system of dozens of medium-orbit satellites. For a variety of reasons, including costs, COMSAT ultimately chose to reject the joint AT&T/RCA offer of a medium-orbit satellite incorporating the best of TELSTAR and RELAY. They chose the 24-hour-orbit (geosynchronous) satellite offered by Hughes Aircraft Company for their first two systems and a TRW geosynchronous satellite for their third system. On April 6, 1965 COMSAT's first satellite, EARLY BIRD, was launched from Cape Canaveral. Global satellite communications had begun.

=A simply fairy tale, the satellite:= **Geosynchronous Orbit (GEO): 35,786 km above the earth**  Geosynchronous satellites orbit at an altitude of 35,786 km above the Earth's surface above the equator, these satellites are stationary relative to Earth and take 24 hours to orbit Earth. Usage -satellite tv

**Medium Earth Orbit (MEO): 8,000-20,000 km above the earth**  Medium earth orbit satellites orbit at an approximate altitude of 14,000 km above the surface of earth, they are placed in elliptical orbits around the north and south poles. Usage -Satellite communication -Certain forms of internet connection such as private networks

**Low Earth Orbit (LEO): 500-2,000 km above the earth**  <span style="color: #515752; font-family: Verdana,Arial,Helvetica,sans-serif;">These orbits are much closer to the Earth, requiring satellites to travel at a very high speed in order to avoid being pulled out of orbit by Earth's <span style="color: #515752; font-family: Verdana,Arial,Helvetica,sans-serif;"> gravity a satellite can circle the Earth in approximately one and a half hours <span style="color: #515752; font-family: Verdana,Arial,Helvetica,sans-serif;">Usage: <span style="color: #515752; font-family: Verdana,Arial,Helvetica,sans-serif;">-Communication <span style="color: #515752; font-family: Verdana,Arial,Helvetica,sans-serif;">-military <span style="color: #515752; font-family: Verdana,Arial,Helvetica,sans-serif;">-Global positioning systems =__**Recent news articles:**__= [|GeoEye Integrates with Google Cloud-Based Map-Publishing Platform] [|Roscosmos Cites Possible ISS Life Extension for Small Satellite Assembly] [|SkyBlue Receives Third Approval Extension for Iridium Frequency Use in China] [|Harris Inks $51.5 Million U.S. Army MET Terminal Order]

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=__**Resources**__= <span style="color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 12pt;">"Space Satellite Desktop Wallpaper : Widescreen : High Definition : Mobile."//WallpapersWide.com | Free High Resolution Desktop Wallpapers for Widescreen, HD, Mobile | Page 1//. Web. 18 Oct. 2011. <http://wallpaperswide.com/space_satellite_6-wallpapers.html>.

"satellite communication -- Britannica Online Encyclopedia." //Encyclopedia - Britannica Online Encyclopedia//. N.p., n.d. Web. 19 Oct. 2011. <[]>.

<span style="color: #000000; display: block; font-family: 'Times New Roman',Times,serif; font-size: 12pt;">"Communications Satellites Short History." //History Home//. Web. 20 Oct. 2011. <http://history.nasa.gov/satcomhistory.html>. <span style="color: #000000; display: block; font-family: 'Times New Roman',Times,serif; font-size: 12pt;">"How Satellite-based Solutions Work? | Tech Talk | Intelsat." //Fixed Satellites and Telecommunications Services | Intelsat//. Web. 20 Oct. 2011. <http://www.intelsat.com/resources/satellite-basics/how-it-works.asp>.