In 1964 more than 100 countries established a commercial global
satellite network known as the International Telecommunications Satellite Consortium (Intelsat), later known as the International Telecommunications Satellite Organisation. Intelsat was an intergovernmental organization managed by the designated communications
entities in their respective countries. The US signatory to Intelsat was COMSAT which, until 1979, handled the management of
the consortium. On 18 July 2001 the International Telecommunications Satellite
Organisation was privatised to become Intelsat Ltd.
The first Intelsat satellite, Early Bird 1, was launched on 6 April
1965 over the Atlantic Ocean to provide 240 voice channels
between the United States and Europe. Commercial satellite communications were
born on 28 June 1965 when Early Bird I commenced
routine operations. The satellite weighed 34 kg, had a transmitter
output power of 40W and provided two 25-MHz transponders with
uplinks/downlinks centred at 6.3/4.2 GHz for Europe and 6.4/4.1 GHz
for the United States. Despite having an original design life
of only two years, Early Bird I remained active until
Intelsat II was launched in 1967 with a weight
of 76 kg and a total transponder bandwidth of 130
MHz providing 240 voice channels, which was increased to a
weight of 152 kg and a bandwidth of 360 MHz
and 1 500 voice channels for Intelsat III.
IV represented a significant step up in capability with a
595-kg satellite providing a 450-MHz bandwidth for 5 000 channels.
The new generation of spacecraft introduced a modification to spin
stabilisation as well as the concept of frequency reuse through
which the satellite’s 500-MHz bandwidth could be doubled by transmitting
two independent, shaped, hemi-spherical beams. Since then modern communication satellites
employ a number of beams to increase capacity and to
maximise power onto subscriber communities. Eight Intelsat IV satellites
were launched (with one failure on launch) providing service between
1971 and 1985.
Continued expansion in demand meant that the original
C-band frequencies were becoming congested, so Intelsat V satellites
added polarisation discrimination to further double the frequency re-use capability
of Intelsat IV, as well as introducing Ku-band spot
beams. The spacecraft weight was increased to 1 020 kg
with 2 250 MHz of bandwidth providing 24 000 voice
channels and two television channels. The Intelsat V spacecraft
changed from spin stabilisation to three-axis stabilisation. Intelsat V-A
also included a maritime communication payload similar to that provided
by Marisat. Of fifteen Intelsat V/V-A satellites launched since
1980, only one remains in service.
From 1986, Intelsat
VI satellites provided another quantum increase in platform weight to
1 800 kg with 3 360 MHz of bandwidth providing
in excess of 33 000 voice channels and two television
channels. Five Intelsat VI satellites remain in service.
Four Intelsat VII-VII/A satellites are in service in the Atlantic Ocean
Region, one in the Indian Ocean Region, and two in
the Pacific Ocean Region.
Four Intelsat VIII satellites are
in service with two in each of the Atlantic and
Pacific Ocean Regions. The Intelsat VIII-VIII/A series incorporates six-fold
C-band frequency re-use and two-fold frequency re-use of expanded C-band
The Intelsat IX series includes seven current satellites—four
over the Atlantic and three over the Indian Ocean. Because
of their high power, Intelsat IX satellites also reduce
Earth segment costs and facilitate services such as satellite news
gathering (SNG), demand-assigned multiple access (DAMA), Internet, direct-to-home (DTH) and
very small aperture terminals (VSAT) networks.
Two Intelsat X satellites
(Intelsat 10-01 and 10-02) are planned for 2003/04 to
cover the whole American continent as well as Western Europe.
The satellites will have a launch mass of around 5
000 kg and a payload power of approximately 8 kW.
One satellite will carry 36 C-band and 20 Ku-band transponders,
while the other will carry 45 C-band and 16 Ku-band
Other topics in our resources on Satellite Communications related to Intelsat include: