Vision of Joint STARS

June 1, 1989

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 ago.”

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 sensor.

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 soft­ware challenge.

Meeting the Challenges

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 Colo­nel Colligan.

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 specifications later.

Increased Precision

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 square kilo­meters.

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 verified.

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 operational users.

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.”

Sharing Data

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 data.

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’vet 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 priorities.

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.”

New Development Problems

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, I’m happy.”