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.
Notes
References
External links
- "The Stay-Putnik", a March 1963 Popular Science article on Syncom 1
- Boeing: Detailed LEASAT information
- Boeing: Detailed Syncom information
- Daniel R. Glover's page about NASA Experimental Communications Satellites
- NASA Goddard Space Flight centre descriptions:
- Gunter's Space Page:
- href="http://www.skyrocket.de/space/doc_sdat/leasat.htm">http://www.skyrocket.de/space/doc_sdat/leasat.htm Leasat 1-5 (Syncom-IV 1 to 5)
syncom in German: Syncom 2
syncom in Finnish: Syncom