AskDefine | Define syncom

Extensive Definition

Syncom (for "synchronous communication satellite") started as a 1961 NASA program for active geosynchronous communication satellites, all of which were developed and manufactured by Hughes Space and Communications. Syncom-2 was the world's first geosynchronous communications satellite, in 1963.
In the 1980s, the series was continued as Syncom IV with some much larger satellites, also manufactured by Hughes. They were leased to the United States military under the LEASAT programme.

Syncom 1, 2 and 3

Common features

The three early Syncom satellites were experimental spacecraft built by Hughes Aircraft Company's facility in Culver City, California. All three satellites were cylindrical in shape, with a diameter of about 71 cm and a height of about 39 cm. Pre-launch fuelled masses were 68 kg, whilst orbital masses were 39 kg with a 25 kg payload. They were capable of emitted signals on two transponders at just 2 W. Thus, Syncom satellites were only capable of carrying a single two-way telephone conversation, or 16 Teletype connections.

Syncom 1

Syncom 1 was to be the first geosynchronous communications satellite. It was launched on February 14 1963 with the Delta B #16 launch vehicle from Cape Canaveral, but was lost on the way to geosynchronous orbit due to an electronics failure. Seconds after the apogee kick motor for circularizing the orbit was fired, the spacecraft fell silent. Later telescopic observations verified the satellite was in an orbit with a period of almost 24 hours at a 33° inclination.

Syncom 2

This was the first geosynchronous communication satellite. Its orbit was inclined rather than geostationary. The satellite was launched by NASA on July 26 1963 with the Delta B #20 launch vehicle from Cape Canaveral. The satellite successfully kept station at the altitude calculated by Herman Potočnik Noordung in the 1920s.
For a time, a ship, the USNS Kingsport, acted as a control station and uplink station for this satellite.

Syncom 3

This satellite was the first geostationary communication satellite, launched on August 19 1964 with the Delta D #25 launch vehicle from Cape Canaveral. The satellite, in orbit near the International Date Line, was used to telecast the 1964 Summer Olympics in Tokyo to the United States. It was the first television programme to cross the Pacific ocean.

Syncom IV (LEASAT)

The five satellites of the 1980s Leased Satellite LEASAT program were alternatively named Syncom IV-1 to Syncom IV-5. These satellites were considerably larger than Syncoms 1 to 3, weighing 1.3 tonnes each (over 7 tonnes with launch fuel). At 4.26 m (14 ft), the satellites were the first to be designed for launch from the Space Shuttle's payload bay.
Hughes was contracted to provide a worldwide communications system based on four satellites, one over the continental United States (CONUS), and one each over the Atlantic, Pacific, and Indian oceans. Five satellites were ordered, with one as a replacement. Also part of the contract was the associated control systems and ground stations.
LEASAT F1's launch was cancelled just prior to lift-off and F2 became the first into orbit on August 30 1984 on shuttle mission STS-41-D. F1 was launched successfully on November 8 1984 followed by Leasat F3 April 12 1985 on STS-51-D. F3's launch was declared a failure when the satellite failed to start its manoeuvre to geostationary orbit once released from Discovery. On August 27 1985 Discovery was again used to launch LEASAT F4, and during the same mission (STS-51-I) captured and repaired F3. F3 successfully fired its perigee motor and obtained a geostationary orbit, however F4 would later fail and was declared a loss.
The fifth and last Leasat (F5), which was built as a spare, was successfully launched by Columbia mission STS-32 on January 9 1990.
The last LEASAT was retired February 1998.



External links

syncom in German: Syncom 2
syncom in Finnish: Syncom
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