Mary Ann Peto
Smart Communications Satellite Managed by NASA Lewis Research Center
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
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
ACTS provides the necessary technologies for:
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.
- 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
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.
Satellite Overall Description
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.
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.
The ACTS ground segment comprises the ACTS master ground station, the satellite operations center and the experimenter
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.
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
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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