TRW Digital Processing and Antennas Boost Battlefield Capability of Milstar II Satellites
Milstar
Flight 4, set to launch Feb. 24, carries TRW-built high-speed,
on-board digital switching and antennas that automatically counter
enemy signal jamming.
In orbit, these new technologies will make Flight 4 the first
satellite to deliver secure, on-demand mobile broadband communications
to U.S. warfighters.
The advanced TRW technologies are part of a new medium data rate
(MDR) communications payload, debuting on Flight 4 (for photos and
more information go to the Milstar Flight 4 News Center). The ability
to communicate at MDR speeds enables the latest Department of Defense
Milstar satellite to provide high-speed transmission of maps,
reconnaissance data, and other digitized, tactical information to
commanders and troops in the field. Two Milstar satellites currently
in orbit communicate at much lower data rates.
“This launch brings 21st century data capabilities to American
forces,” said Rick Braun, TRW’s Milstar payload program manager. “The
TRW-developed fast digital switching and nulling antennas of Milstar
Flights 4 through 6 will permit U.S. military forces anywhere on
Earth, equipped with only small terminals, to communicate securely at
rates as high as 1.544 million bits per second (Mbps). That’s roughly
30 times faster than the modems on most personal computers today.”
The low data rate (LDR) payload aboard Milstar Flights 1 and 2
(referred to collectively as Milstar I) transmits data at a maximum
rate of 2400 bps. Flights 4 through 6 (known as Milstar II) will fly
both an MDR and LDR payload. The LDR payload provides highly robust,
global communications links under even the most severe battle
conditions, ensuring high-security support for the U.S. Department of
Defense’s strategic mission.
Lockheed Martin Space Systems is system integrator and contractor
to the U.S. Air Force for the joint-services Milstar program. Boeing
Satellite Systems integrates the MDR payload for Lockheed Martin,
while TRW is subcontractor to Lockheed Martin for the LDR and supplies
Boeing with MDR antennas and the digital processing subsystem.
On-board Digital Processing
Key to Dynamic Milstar Communications Milstar’s LDR and MDR
payloads function as “switchboards in space,” providing users with
circuits on demand. This digitally controlled approach allows easy
reconfiguration of satellite resources to meet constantly shifting
requests for service from rapidly changing user networks. Digital
signal processing also enables use of spread-spectrum techniques that
help defend Milstar signals from jamming.
Milstar is the first satellite system to operate only at extremely
high frequencies (EHF), with uplinks at 44 GHz and downlinks at 20
GHz. Operating at EHF yields a number of benefits, including the
ability to produce narrow spot beams. These spot beams provide higher
gain, permitting the use of smaller, easily portable Earth terminals
with small antennas. The smaller area of beam coverage drastically
lowers the probability of the Milstar signal being detected or
intercepted by enemy forces.
Advanced Antennas Foil Jammers, Serve Dispersed Users
The MDR’s two nulling spot beam antennas instantly detect enemy
signal jamming and counter it within a fraction of a second by placing
a “null” in the jammer’s direction. (In antenna terminology a “null”
is a direction from which an antenna collects very little energy. The
null minimizes the strength of the jammer’s signals, while maximizing
the strength of Milstar users’ signals.) These nulling antennas are
the first ever to perform nulling autonomously, with no commands from
the ground. The nulling capability is vital for theater applications,
where jammers may be located close to Milstar users in the same
antenna coverage area.
Complementing the MDR nulling antennas are six distributed user
coverage antennas (DUCAs). DUCAs better match the needs of dispersed
global users such as the U.S. Navy, whose ships are less likely to be
near jamming stations.
The DUCAs incorporate important advances in manufacturing
techniques. The payoffs: TRW was able to lower costs by more than 60
percent and slash weight by 72 percent as compared with the
counterpart antennas on Milstar I satellites. The weight savings
provided some of the margin needed to achieve the MDR’s greater data
rate and nulling capabilities.
Beyond Milstar, in May 2000, TRW joined with Lockheed Martin and
Boeing Satellite Systems to form the Advanced Extremely High Frequency
(Advanced EHF) National Team to build the follow-on to the Milstar
highly secure communication satellite program. Formation of the team
accelerates development of the new system by 18 months. The earlier
deployment of Advanced EHF will help bridge the gap in military
communication coverage caused by the loss of the third Milstar
satellite, launched in 1999.
Under the National Team arrangement, TRW will design and produce
the Advanced EHF satellites’ digital processing subsystem, which
controls all on-board switching and processing of messages. TRW will
also provide the satellites’ nulling antenna subsystem, which prevents
adversaries from jamming signals to and from the satellite, and the
intersatellite crosslinks with support from Boeing for the crosslink
reflectors. Crosslinks enable Advanced EHF satellites to send messages
directly to each other, without the need for a ground station. First
launch is planned for 2004.
TRW Space & Electronics Group is a global leader in the
development of digital, broadband space communications payloads for
defense and commercial customers. It is an operating unit of TRW Inc.,
which provides advanced technology products and services for the
automotive, space and defense, telecommunications and information
technology markets worldwide. Information about the company is
available at www.trw.com.
