A two-way digital voice terminal for land, aeronautical or maritime mobile communications has been demonstrated in the field for the first time by Jet Propulsion Laboratory researchers.
The trial, which took place in late March 1989, is believed to be the first-ever field test of state-of-the art low-bit-rate voice coder over an on-orbit satellite in commercial application.
During the tests, researchers used voice terminal on Boeing 727 to communicate with ground station in Southbury, Connecticut. The jet, based out of Atlantic City, New Jersey, was airborne over the eastern U.S. seaboard during the tests.
Signals were relayed between the plane and ground by an orbiting satellite operated by the International Maritime Satellite (Inmarsat) organization.
"The system we demonstrated is type that would be beneficial for planes in transit over the Atlantic Ocean," said Dr. William Rafferty, manager of JPL's Communications Section, which conducts the Mobile Satellite Experiment (MSAT-X) program for NASA.
Planes flying over the Atlantic currently must relay communications at times through other planes on the ocean route. mobile satellite communication system would link each plane to ground stations via satellite.
The terminal system demonstrated during the test uses 4.8-kilobit-per-second digital voice system developed at JPL. Advanced digital modulation and coding techniques are used to achieve highly efficient channel bandwidth of 5 kilohertz.
Under the MSAT-X program, JPL has been developing technologies that would be useful in mobile satellite systems. Areas of research include mechanically and electronically steered vehicle antennas, modulation encoding and networking methods.
fully developed mobile system would use satellites to extend mobile telephone services to remote ground users and to users in the air and on the sea who cannot be served by cellular telephone systems.
In addition to planes in flight and ships at sea, such system could also serve such users as private drivers, cross-country trucks, forestry personnel and law-enforcement agents.
JPL's role is strictly to develop new technologies required for mobile satellite system. NASA plans to seek cooperative agreements with the commercial operator of first-generation satellite system whereby the space agency will launch the first satellite. In exchange, NASA would be able to conduct technology validation experiments using small percentage of the satellite's capacity for the first two years of operation.
Rafferty said plans call for JPL land mobile experiment in Australia during July 1989. The location of that test will make use of favorably situated on-orbit satellite.
The March test was made possible through the cooperation of the U.S. Federal Aviation Administration, which operates the Boeing 727 research jet used in the experiment. Inmarsat and its U.S. signatory, Comsat Inc., provided ground facilities.
MSAT-X is funded by the Communications and Information Systems Division of NASA's Office of Space Science and Applications.
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