Customers Opt for HAC Satellites Hughes News March 30, 1973

Intelsat Chooses Hughes to Build IV-A Spacecraft

The Board of Governors of Intelsat has approved a $72 million contract with HAC for three advanced synchronous communications satellites to be used beginning in mid-1976.

The contract will be administered by Comsat, acting as manager, on behalf of the International Telecommunications Satellite Organization.

Designated the Intelsat IV-A series, the new satellite will have almost twice the communications capability of the present global system of Hughes-built Intelsat IV satellites operating over the Atlantic, Pacific, and Indian Oceans.

20 Transponders

The new satellites, derived from the highly successful Intelsat IV series, will have 20 transponders compared with 12 for the IVs.

Where the Intelsat IV satellites, which introduced the spot beam concept, are designed to use a maximum of eight transponders in spot beam mode, the IV-A satellites will be designed to use a maximum of 16 transponders in the spot beam mode. As with the IVs, the remaining transponders in the IV-As would be used in global mode coverage. In this mode, transponders are focused on an area a little larger than one third of the world. Spot beams concentrate a satellite’s power on smaller, selected areas with the satellites total coverage.

Frequency Reuse

In addition, the IV-A satellites will employ frequency reuse through spot beam separation, a concept not included in the IV spot beam capability. Beam separation permits communications to go in different directions on the same frequencies by using different transponders making double use of the same frequency.

The IV-As will make far more efficient use of the satellite communications frequency bands.

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About Jack Fisher

Jack was a systems engineer at Hughes from 1961 to 1992. He contributed to various programs including Surveyor, Pioneer Venus, Galileo, Intelsat VI and innumerable proposals. He was the manager of of the Spacecraft Systems Engineering Lab until his retirement. Upon retirement Jack taught systems engineering at a number of national and international venues.