unitex@rubbs.fidonet.org (unitex) (10/02/89)
NASA MOBILE COMMUNICATIONS SYSTEM FIELD TESTED
Posting Date: 09/30/89
UNITEX Network, USA ISSN: 1043-7932
A complete system for mobile communications has been field-
tested for the first time by researchers from NASA's Jet
Propulsion Laboratory (JPL), Pasadena, Calif.
A fully developed system would use satellites to extend mobile
telephone services to remote ground users and to users in the
air and at sea who cannot be served by cellular telephone
systems. Such a system also could serve such users as private
drivers, cross-country trucks, forestry personnel and law-
enforcement agents.
The field tests were made possible by the cooperation of AUSSAT
Pty. Ltd., the Australian national satellite system, which
provided local facilities used in the experiments.
The experiments, conducted in July and August 1989, involved
communications between a base at AUSSAT's downtown Sydney,
Australia, facility and a mobile unit mounted in a van. The
system evaluated in the tests uses vehicle antennas, voice
encoders and other hardware developed by JPL under its Mobile
Satellite Experiment (MSAT-X) program for NASA.
"Our conclusion was that the system really will work," said Dr.
William Rafferty, manager of JPL's Communications Section. Both
voice and data calls were tested during the experiments, he
said.
During the tests, the mobile unit ranged as far away as the city
of Brisbane, more than 450 miles north of Sydney. That is
approximately the distance between Los Angeles and San Francisco
or between New York City and Detroit. According to Rafferty,
routes followed by the mobile unit took it behind trees, under
bridges and around other obstructions, with no loss of
synchronization, during calls lasting more than 2 hours each.
Calls were relayed over Japan's Experimental Technology
Satellite-V. When fully operational, mobile communications
systems would use special, dedicated Earth-orbiting satellites.
Under the MSAT-X program, JPL has been developing technologies
for mobile satellite systems, including mechanically and
electronically steered vehicle antennas, modulation encoding and
networking methods.
This summer's tests included secure calls in which digital voice
transmission was encrypted. This technique would be important
to user agencies participating in the U.S. National
Communications System such as the FBI and the Drug Enforcement
Agency, Rafferty said.
JPL's role is strictly to develop new technologies required for
a mobile satellite system. NASA plans to seek cooperative
agreements with the commercial operator of a first-generation
satellite system whereby the space agency would launch the first
satellite. In exchange, NASA would be able to conduct technology
validation experiments using a small percentage of the
satellite's capacity.
Now that a prototype system has been demonstrated, Rafferty
said, MSAT-X work at JPL will shift to more "applications-
oriented" issues.
MSAT-X is funded by the Headquarters Communications and
Information Systems Division of NASA's Office of Space Science
and Applications, Washington, D.C.
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