PRESS RELEASE 93-42

Immediate 
Mary Ann Peto
(Bus: 216/433-2902)
<h3>Smart Communications Satellite Managed by NASA Lewis Research 
Center</h3> Cleveland, OH -- When space shuttle Discovery is launched 
this month, nestled in its payload bay will be NASA's Advanced 
Communications Technology Satellite (ACTS). The development of this 
highly experimental communications satellite was managed by engineers 
at the NASA Lewis Research Center in Cleveland.

Dr. Richard Gedney, manager, ACTS Project Office, said, "The new 
technology ACTS offers could revolutionize the communications 
industry. And," he further indicated that, "as an experimental 
satellite, ACTS is paving the way for future communications 
satellites, reducing the risks for commercial use before the 
technology is adapted by industry."

ACTS is the first U.S. communications satellite to operate in the Ka 
band. ACTS technologies, which are applicable for a variety of 
frequency bands, will potentially lower the cost or technical 
threshold, making new services possible.

Consequently, medical specialists at the Mayo Clinic could perform 
life-saving medical image scanning diagnoses via satellite for 
patients in rural areas, allowing those patients to have the same 
advantages as patients located at the Clinic in Rochester, Minnesota.

Institutions such as The Huntington National Bank and Ohio University 
will work with Lewis to test the feasibility of using ACTS' 
technology to transmit financial data via satellite to provide a 
back-up system in the event of a disaster that would disrupt land 
communication lines.

As the nation moves into the 21st century, new space communications 
systems will be required to meet the expanding demand for 
communication services.

Today's space communication systems evolved from the high-risk 
technology developed and flight tested by NASA via the Synchronous 
Communications Satellite (SYNCOM), the Applications Technology 
Satellite (ATS) series and the Communications Technology Satellite 
(CTS). Space communications systems of the 1990's and beyond will 
require further revolutionary advances in technology to permit more 
efficient use of orbit and spectrum resources and to allow for new 
forms of information transfer.

ACTS will pioneer new high-risk technologies and will usher in NASA's 
reentry into the development and flight testing of communication 
satellites. 

ACTS provides the necessary technologies for:



Operation in the Ka band (30/20 gigahertz) -- first U.S. satellite to 
do so

Very high-gain, multiple-hopping-beam antenna systems, which permit 
smaller aperture Earth terminals

Onboard baseband switching, which interconnects users at an individual 
circuit level

Microwave switch matrix, which enables gigabit-per-second 
communications between users

These technologies provide as much as three times the communications 
capacity for the same weight as today's satellites and therefore are 
more cost effective. They offer much higher data rate communications 
between users and provide greater networking flexibility and 
on-demand digital services not available from communications systems 
today. 

ACTS technologies, which are applicable for a variety of frequency 
bands, will potentially permit new services as remote medical image 
diagnostics, global personal communications, real-time TV 
transmissions to airliners, direct transmission of reconnaissance 
image data to battlefield commanders and interconnection of 
supercomputers. 

<h3>Satellite Overall Description</h3> The ACTS is made up of a 
spacecraft bus with basic housekeeping functions and a payload known 
as the multibeam communications package (MCP). When on-orbit the 
large antenna reflectors face the Earth and the solar array panels 
rotate once per day to track the Sun. During the launch and transfer 
orbit phase of the mission, the antenna reflectors and solar array 
panels are retracted and stowed to provide better load support for 
these appendages. The multibeam antenna subsystem is mounted to the 
Earth-facing antenna panel of the spacecraft bus. The north and south 
panels of the bus contain the remainder of the MCP hardware.

<h3>Mission Sequence</h3> Approximately eight hours after launch, 
ACTS, attached to the Transfer Orbit Stage (TOS), will be released 
from the payload cargo bay. The TOS motor firing will be controlled 
by the onboard timer and will occur 45 minutes after deployment from 
the orbiter. The approximately two-minute burn will place ACTS in the 
geotransfer orbit. Fifteen minutes after burnout ACTS will fire 
pyrotechnic charges that will separate the clampband attaching ACTS 
to TOS. Four springs in the adapter will push the spent TOS away from 
the spacecraft. The apogee kick motor burn to inject ACTS into drift 
orbit will take place about 42 hours after deployment. ACTS will 
drift for seven days, moving toward its final station location of l00 
degrees west longitude and approximately 22,300 miles from Earth 
directly above the equator.

Upon reaching geostationary orbit, the spacecraft will acquire Earth 
and Sun lock, deploy its solar arrays and deploy the communications 
antennas. These maneuvers will take approximately 14 hours.

ACTS experiments will begin 12 weeks after launch when the spacecraft 
is on station and checked out.

<h3>Ground Segment</h3> The ACTS ground segment comprises the ACTS 
master ground station, the satellite operations center and the 
experimenter terminals.

Master ground station - The ACTS master ground station is located at 
the NASA Lewis Research Center in Cleveland, Ohio. It includes the 
NASA ground station, the microwave switch matrix-link evaluation 
terminal and command, ranging, and telemetry equipment. 

Satellite operations center - The satellite operations center is at 
the Martin Marietta Astro-Space facility in East Windsor, New Jersey. 
It has primary responsibility for generating flight system commands 
and for analyzing, processing and displaying flight system telemetry 
data. It also handles orbital maneuver planning and execution, and 
performs the primary housekeeping functions. 

Experimenter terminals - The Ka-band experimenter network consists of 
a variety of Earth terminals to be operated by industry, universities 
and government organizations. More than 40 experimenter terminals 
will be used in the Experiments Program.

<h3> Experiments Program</h3> The ACTS Program has developed and will 
validate, by flight testing, high-risk advanced communications 
technologies. The ACTS flight and ground systems will be made 
available to the public and private sectors for evaluation, 
experimentation and demonstration of key technologies and their 
applications after launch. A formal two-year Experiments Program is 
currently planned. However, the spacecraft will have stationkeeping 
fuel for a four-year-plus mission. 

Besides managing the development of ACTS, the Lewis Research Center is 
responsible for the development of the master ground station and 
experimental terminals and management of all experiments to be 
conducted through ACTS.

As in previous shuttle missions, residents of Cuyahoga County and 
boundary county areas with radio frequency scanners can listen in on 
live space shuttle commentary, status reports and mission press 
briefings.

The Lewis Amateur Radio Club is making programming available for this 
and other upcoming shuttle missions by retransmitting the signal. 

Primary frequency for listening to the shuttle audio is 145.67MHz FM, 
with an alternate frequency of 147.195 MHz FM. 

The launch of STS-51 is currently scheduled to lift off no earlier 
than 9:22 a.m. EDT on July 17, 1993.



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