An exotic radar aircraft now beginning to take shape has rekindled
confidence that Air Force technologists will be able to meet one of their most
formidable challenges in years.
The team developing the Joint Surveillance Target Attack
Radar System is no longer a struggling group plagued by setbacks, as in times past.
Joint STARS developers have been staging a comeback for months.
Now, say officers, the technologists seem likely to succeed
in producing the plane that Washington wants to provide big-picture radar
coverage of a ground war in Europe. The E-8A will be the key sensor in a new
plan to locate and attack onrushing Soviet armor. The team run by Electronic
Systems Division (ESD) at Hanscom AFB, Mass., overseer of the $6.6 billion
program, is strengthened by several factors.
These include breakthroughs in operation of the plane's
ultra-complex, steerable, multimode radar; completion of the communications,
navigation, and data-link systems; verification of the test vehicle's
airworthiness; establishment of a workable systems architecture; and the first
production of vital operations and control software.
No one is complacent, but officers are optimistic they can
meet next year's goals of completing development testing and a system-level
performance verification of prime contractor Grumman's total product. "We
could still fail," says Col. John Colligan, the program director.
"But the chances of failure are a lot less than [they were] a year
Washington, too, evidently regards the Joint STARS craft as
a going concern. The Pentagon has given USAF authorization to develop an
electronic-warfare suite for sell-defense, expand force structure from ten to
twenty-two airplanes, procure new airframes rather than used Boeing 707s, and
provide mission simulators—all expensive propositions.
Effects of recent radar breakthroughs are most evident in
the sharp pointing accuracy and precise beam-formation properties that are now
being displayed by the first test airplane's ultrasophisticated electronic
In a series of tests starting last December 22, the 1,700-pound
X-band radar slung under the aircraft has shown its capability to focus intently
on a single spot on the ground and propagate beams of carefully modulated
intensity and shape. The upshot of the tests is summarized by Colonel Colligan:
"Did we prove that a lot of the tough things we wanted
to do have now been done? Yep. Sure did. Will we be able to do the job? Yes.
From the 'does it work?' standpoint, yes, we can make this radar work."
The side-looking radar, built by Norden Systems, can be operated
either in a Doppler mode to detect moving targets or in a synthetic aperture
radar mode to see stationary features. Standing off behind the Forward Line of
Troops (FLOT), the E-8A radar will be able to scan deep into enemy areas in
search of enemy ground activity.
The radar antenna is a large, complex device, steered in
two ways. First, mechanical means are used to set the beam's elevation—the
point at which it strikes the earth. Secondly, the beam is scanned by electronic
means in azimuth. The electronic scanning is carried out by a set of
software-controlled phase-shifters in the antenna, and the operation requires
complex and precisely timed software instructions. Making sure that the
mechanical and electronic operations work together creates an even greater
The Air Force is now confident that it has met those
software challenges. In a six-hour flight of the test aircraft on December 22,
ESD verified that the complex digital steering commands do, in fact, focus
the beam properly. The phase-shifters swept a beam across the earth and
precisely struck a receiving device on the ground.
The December test, program workers note, also showed the
integrity of airborne high-power radar transmission elements. The signals exchanged
between the Joint STARS aircraft and Grumman's ground-based Integration and
Test Facility in Florida confirmed that there was proper formation of the
transmit and receive beams.
"We proved that we could put energy, in a controlled
sense, through the transmitter, through the antenna, on the ground, to a spot
that we could control, in a form of energy that we could control," notes
The radar, unsurprisingly, is not yet working perfectly.
Minor glitches crop up. For example, problems with a Joint STARS inertial
navigation system in one flight threw the radar off, causing it to mistake one
Florida causeway for another nearby. Engineers also found some saturation of
the analog-to-digital conversion system.
"But we're not talking about rocket science here,"
remarks Colonel Colligan. "The important thing is that we understand, and
are proving we understand, the radar software. That was the tough part."
In addition to demonstrations of mechanical capabilities,
progress in verifying the radar's planned target-detection abilities has been
heartening to Air Force officers and their contractors.
The Joint STARS team in recent months has successfully put
together the transmission and receiving functions of the radar. In a test
conducted last March 16, Joint STARS technicians beamed energy to the ground
and got data back in the form of a target for the first time. The process was
repeated days later and has been repeated at regular intervals since.
As a result, ESD is convinced that it has produced workable
clutter-rejection algorithms to differentiate between actual targets and
background. "The guys who know what they're looking at," notes
Colonel Colligan, "say, 'Aha! Here's Cocoa Beach, here's Merritt Island,
here's the mainland, here's the causeway. See the cars.'
Producing this kind of capability has been nothing if not
difficult. Because of the ground-clutter problem, the job of the Joint STARS
radar is more complex than that of the E-3 Airborne Warning and Control
System's radar. The magnitude of radar-processing demands can be seen in the
fact that the Joint STARS signal processor, several programmable units built by
Control Data Corp., perform a staggering 625,000,000 operations per second.
Long months have been spent developing prototype software
containing basic algorithms that make the radar look out and spot a moving
target on a background of clutter. The code will be written to military
From today's relatively rudimentary operations, the radar
is expected to progress to awesome capabilities. That is made plain by Maj.
Gen. Eric Nelson, ESD Vice Commander. In addition to performing broad
surveillance, he says, the radar operator will be able to "get a lot more
precise, put in a lot more cultural data—road networks, cities, political
borders, other reference areas. There will be a zoom capability down to the
individual road, very small towns . . . individual vehicles, to tell which way
they are moving and at what speeds."
The initial phase of airborne radar testing, completed in
April, was limited in scope. It focused on calibrating the Joint STARS radar
performance against targets of controlled size and speed—an officer describes
them as "a few off-road vehicles and four-wheel drives"—operating
in a 100-square-kilometer sector of Florida. While the radar performed well,
it was undermatched. The sensor is built to survey areas as large as 30,000
Demonstrations of wide-area surveillance, which are to
focus on the grounds of Eglin AFB, Fla., and a range in southern Alabama, are
just now getting under way. By summer's end, the Air Force will be pitting
the radar against slow-moving, hard-to-spot targets, such as tanks.
"That's the next step in the process," says Colonel Colligan.
"That's where you really can see how well you can break into the clutter
and bring up a target."
Helping to speed the tests will be full operation, starting
in September, of a second Joint STARS test aircraft.
Joint STARS's prospects had gotten a boost from other
developmental successes. Airworthiness problems—principally, how to control a
craft carrying a large, canoe-shaped radome under its fuselage—were resolved.
Voice communications and navigations systems and software were installed and
More significant was ESD's success in fashioning a new
surveillance and control data link (SCDL) to transmit Joint STARS information
to users on land. The SCDL system, built by Cubic Corp., is pivotal to
Plans call for on-board Air Force systems to convert radar
returns into C31 information. The Army, needing to supply many users at all
levels, will use the SCDL to transmit raw radar returns as well as processed
data to the 107 Joint STARS ground stations it is slated to build.
USAF only recently took delivery of the first full set of
data-link equipment, but it has been flying test parts since September. ESD officers,
Colonel Colligan remarks, have found "very few problems with it. Range,
antijam margins, data rate—we're getting what we need."
Efforts are under way to ensure that Joint STARS data can be
shared with similar NATO battle management systems—France's Orchidée
(Observatoire Radar Coherent Heliporte d'Investigation des Etéments Ennemis)
and Britain's AS-TOR (Airborne Standoff Radar) systems. Cubic's data link will
be used in the British demonstrator. France plans to use its own data link. ESD
will provide an interface permitting interplay of Joint STARS and Orchidée
The ESD program office expresses lack of enthusiasm for
Cubic's management of the effort, which brought in the data link twenty-one
months behind schedule. As a result, Grumman has opened discussions with three
other potential contractors—Harris Corp., General Dynamics, and Unisys—about
prospects for modifying an existing data link to do the job. A final decision
lies several months ahead.
How far the technology program has come, and has yet to go,
is nowhere clearer than in operations and control features—functions for
manipulating the radar information into usable data. As ESD officials tell it,
Grumman has made steady strides in this difficult area.
The company has established what appears to be a realistic,
workable architecture for integrating the various radar functions into a harmonious
electronic whole. "There are three kinds of guys working on this program:
brilliant, very smart, and smart," comments a program officer. "We've
got an architecture that the brilliant guys say will work. The very smart guys
are implementing it. We're making progress."
The challenge stems from the unprecedented complexity of
Joint STARS's data-processing system. It does not have a central control computer.
Instead, the craft will use twenty-seven processors that enable large numbers
of computer functions to occur in parallel. The object is to allow processed
radar data to be displayed in different forms at the same time at any of the
aircraft's ten full-color operator consoles.
This system accounts for the aircraft's vast software
requirements. At present, plans call for Joint STARS to run about two million
lines of code, some 600,000 lines of it new and complicated. A large fraction
of this total focuses on operations and control. Today, all Grumman software
has passed through preliminary design, half of it through detailed design, and
a third of it through code-writing.
Still, experts such as Colonel Colligan regard operations
software as the most likely place where Joint STARS may be tripped up. "If
you talk to Grumman guys, they'll say they're getting a handle on the radar
software," says the colonel. "But we've asked them to do an awful lot
of things to make this data have very high utility for the operator. Doing all
that simultaneously is going to be a tough job. We've said we want all ten
consoles to be completely independent. Each one of these guys ought to be able
to act like it's his radar."
In the end, some maintain, the Air Force may have to relax
or modify some of its ambitious goals. This could have a relatively modest impact.
For example, time required to provide a complete replay of the foregoing three
hours of radar data, now planned at thirty seconds, may go up to forty-five
seconds. Other functions could be affected more seriously or dropped
altogether. ESD is consulting with Tactical Air Command to establish
All signs are that Grumman faces a workable, but tight,
development schedule. The contractor will have to complete some ninety-five percent
of its software before the start of the demanding, three-month, system-level
performance verification tests. That could come as early as next summer, but
in any case no later than November 1990, barring a major snag in the program.
Officials say Grumman looks to be on schedule. But, one acknowledges,
"There's a very tough integration job in front of us."
The Pentagon, persuaded that Joint STARS is here to stay,
has reshaped and expanded the program. The steps will require new attention
from the developers.
Most conspicuous, but by no means most important, is the new
technological task caused by Pentagon approval of a different airframe for
the E-8A role. Originally, plans called for the use of older, refurbished
Boeing 707 commercial aircraft for the Joint STARS fleet. In 1988, the Air
Force selected and the Pentagon approved use of new
707-320 frames, the same used by the Navy for its E-6A
plane. The changeover, however, will pose no great technological challenge. It
will entail installation in the Air Force E-8 of a cargo floor not found in the
Navy E-6 and perhaps minor structural alterations.
Another Pentagon decision—to fit future Joint STARS aircraft
with self-defense suites to enhance their survivability—will not be executed so
readily. ESD is in the throes of an effort to examine its needs, define the
system it wants, and determine the fastest, cheapest, and least disruptive way
to install it.
There is little doubt that such a system is needed. From the
beginning, experts within and outside the Air Force—particularly the chief of
the Pentagon's systems analysis office, Deputy Assistant Secretary David
Chu—warned that a large, slow-flying, and extremely valuable aircraft would
present a tempting target.
The matter came to a head last year with completion of a new
Pentagon analysis. "Basically," says Colonel Colligan, "the
conclusion reached was that we're pretty survivable, with the defenses that
are in place, at standoff ranges from the FLOT. But there, we couldn't provide
as much utility [to Western forces] as we would like. We would not be looking
as deep as we would like to look, obviously."
In order to operate closer to the front with security, he
adds, Joint STARS requires an EW suite to deal with a "leaker," a
single aircraft that gets close enough to take a potentially lethal shot.
ESD has hired a contractor to examine the problems and solutions.
Electronic-warfare specialists based at Aeronautical Systems Division are
being consulted. Possibilities include installation of a radar warning
receiver, approach warning radar, flares, chaff, and a deceptive jammer.
Even if ESD uses existing equipment, as it plans to do, new
development costs could reach $200 million. Final decisions are not expected
for another year, and first tests will not take place until 1992 when the third
test aircraft becomes available.
One aspect of the aircraft, a weapons data link, is in
limbo. Part of the initial Joint STARS plan approved in 1985, the link was supposed
to permit the radar to broadcast present target positions to a black box
resident on an airplane or a missile. Inasmuch as no one has developed the
black box, ESD has declined to spend money developing the 15,000 lines of
software needed for the link.
If events go as planned, the Grumman system-level performance
review will be followed by long-lead funding for the first production aircraft
and the start of initial operational tests, which would run through 1991. An
Air Force production decision would come in October 1991, with deliveries
starting in 1994 and limited operation in 1995.
There is optimism that the timetables will hold.
"Basically, we're keeping to the plan that we laid out for the
leadership," says Colonel Colligan. "If we can continue to do. that,
Daily Report: Read the day's top news on the US Air Force, airpower, and national security issues.
Read the day's top news on the US Air Force, airpower, and national security issues.
Daily Report: Read the day's top news on the US Air Force, airpower, and national security issues.
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