Intelsat is an organization (International Telecommunications Satellite Organization) formed in 1964 that designs, builds, and operates a global system of communications satellites of the same name. For most of its life, Intelsat was run by a consortium of government telecommunications authorities with shares in the organization in proportion to their use of it. However, in 2000, the nearly 150 member nations agreed to turn the enterprise from a treaty-based organization into a privately held company. The following year, Bermuda-based Intelsat Ltd was formed.

 

Intelsat 1, also known as Early Bird, was launched in April 1965 and became the first comsat to provide regular commercial telecommunications. It could support either one TV channel or 240 voice circuits but not both, a limitation that made it costly to use. In the spring of 1967, Early Bird was joined by two larger companions – Intelsat 2 over the Pacific and Intelsat 3 over the Atlantic. With these three satellites, all the world's TV networks could be linked together, and the first global telecast was broadcast on 27 June 1967.

 

During the 1960s and '70s, message capacity and transmission power of the Intelsat 2, 3, and 4 generations were progressively increased by segmenting the voice circuits into more and more transponder (transmitter-receiver) units, each having a certain bandwidth. The first of the Intelsat 4 series, launched in 1971, provided 4,000 voice circuits. With the Intelsat 5 series (1980), the introduction of multiple beams directed at the Earth resulted in even greater capacity. A satellite's power could now be concentrated on small regions of the planet, making possible lower-cost ground stations with smaller antennas. An Intelsat 5 satellite could typically carry 12,000 voice circuits. The Intelsat 6 satellites, which entered service in 1989, can carry 24,000 circuits and feature dynamic onboard switching of telephone capacity among six beams, using a technique called SS/ TDMA (satellite switched/time-division multiple access). Intelsat 7 satellites provide up to 112,500 voice circuits and three TV circuits each, depending on the market needs in the orbital location. Satellites in the most recently completed series, Intelsat 8 and 8A, launched in the late 1990s, can simultaneously handle 112,500 phone calls, or 22,000 phone calls plus three color TV broadcasts. These are now being joined by a 10-strong fleet of the even more powerful Intelsat 9, each carrying 72 C-band and 22-Ku-band transponders (see frequency bands). When the new fleet is in place by 2003–2004, Intelsat expects to have a constellation of 24 operational satellites, supplemented by over 600 Earth stations.

 

spacecraft series	no.	launch dates	launch vehicle	capacity	mass
Intelsat 1	1	Apr 1965	Delta D	240 voice or 1 TV	39 kg
Intelsat 2	3	Jan 1966-Sep 1967	Delta E	240 voice or 1 TV	87 kg
Intelsat 3	5	Dec 1968-Apr 1970	Delta M	1,500 voice or 4 TV	287 kg
Intelsat 4	7	Jan 1971-May 1975	Atlas-Centaur	4,000 voice or 2 TV	1,410 kg
Intelsat 4A	6	Sep 1975-Mar 1978	Atlas-Centaur	7,250 voice or 2 TV	1,520 kg
Intelsat 5	8	Dec 1980-Jun 1984	A-C, Ariane 1, Atlas G	12,000 voice + 2 TV	2,000 kg
Intelsat 5A	6	Mar 1985-Jan 1989	Atlas G, Ariane 2/3	15,000 voice + 2 TV	2,013 kg
Intelsat 6	4	Oct 1989-Oct 1991	Ariane 4	24,000 voice + 3 TV	4,300 kg
Intelsat K	1	Jun 10, 1992	Atlas IIA	32 TV	2,930 kg
Intelsat 7	6	Oct 1993-Jun 1996	Ariane 4, Atlas IIAS	18,000 voice + 3 TV	4,200 kg
Intelsat 7A	3	May 1995-Feb 1996	Ariane 4, CZ-3B	18,000 voice + 3TV	4,500 kg
Intelsat 8	4	Mar 1997-Dec 1997	Ariane 4, Atlas IIAS	22,000 voice + 3 TV	3,400 kg
Intelsat 8A	2	Feb - Jun 1998	Atlas IIAS	22,000 voice + 3TV	3,520 kg
Intelsat 9	7	Jun. 2001-	Ariane 4, Proton-K	76 C-band + 24 Ku-band transponders	4,724 kg