A new application of synchronous satellite communications technology was unveiled in
1976 with a three-ocean maritime satellite system that is providing telecommunications
services in the Atlantic, Pacific, and Indian Oceans.
Hughes Aircraft Company under contract to Comsat General Corporation built three
multifrequency communications spacecraft called Marisat for the space segment of the
world's first maritime system. All three satellites were launched during 1976, one each on
February 19, June 9, and October 14. The satellites were placed in geosynchronous orbit at
15 degrees W, 176.5 degrees E, and 72.5 degrees E longitude, respectively.
The specialized satellites introduced a new communications capability since they
provide service in three different frequencies simultaneously--ultrahigh frequency (240 to
400 MHz), L-band (1.5 to 1.6 GHz), and C-band (4 and 6 GHz). UHF frequencies are used by
the U.S. Navy communication links between shore and shipboard terminals and the
satellites. Commercial maritime services include voice, teletype, facsimile, and high
speed data. L-band frequencies are used for commercial communications from ship to
satellite. The C-band frequencies are used for commercial communications links between the
satellites and Earth stations on each coast of the United States. Satellite tracking,
telemetry, and command functions also are conducted over C-band frequencies.
Before the launch of Marisat, the American Institute of Merchant Shipping emphasized
the need for functional transoceanic communications to maintain ship-to-shore contact with
globe-circling ships on the high seas. According to the Institute, ship owners had
previously reported being out of contact with their ships for as long as 48 hours, and the
average delay for a message had been about 12 hours.
For commercial shipping, the Marisat system is providing high quality communications
channels around the clock.
Launch vehicle for the satellites was the McDonnell Douglas Delta-2914. At liftoff, Marisat weighed about
1450 pounds (656 kilograms). Each satellite is 12 feet 6 inches (3.81 meters) in height
and 7 feet 1 inch (2.15 meters) in diameter. A cylindrical solar panel, covered with
approximately 7000 solar cells, supplies each satellite with primary power of 330 Watts.
The satellites were launched from Cape Canaveral by the National Aeronautics and Space
Administration under contract with Comsat General.
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