Joint STARS

We mentioned the other day the damage to an E-8C due to a refueling error. The E-8C was the Air Force response to a Cold War need for battlefield surveillance.

It comes as no surprise that the Air Force doesn’t really like the Close Air Support mission. And to a certain extent, they’ve got a point. They’re happy enough to do it in circumstances such as in Iraq and Afghanistan. But back in the Cold War era, when NATO was staring tens of thousands of Warsaw Pact armored vehicles lined up against relatively modest numbers of friendly forces, the idea of using a $10 million dollar F-4 to take out a $500,000 T-72 really didn’t make sense.  But if that same F-4 could strike at an entire battalion of tanks in march column, well that’s another story. Cluster munitions would allow one F-4 to damage or destroy the entire column with just one pass. That mission, striking formations behind the lines before they have a chance to deploy, is known as Battlefield Air Interdiction, or BAI, and the Air Force put billions of dollars into developing the means to accomplish it.  Just a few of the programs involved include LANTRIN, an entire family of anti-armor munitions (often specialized cluster munitions), the TR-1 (a modified U-2 platform for battlefield surveillance)  and the subject of this post, the Joint STARS, or Joint Surveillance, Target, Attack Radar System.

E-8C

E-8C Joint STARS

The Army had a similar problem. Its AirLand Battle Doctrine relied heavily on brigade, division and corps commanders being able to see the battlefield, find and exploit weak spots in the enemy’s formations, and influence where and when the enemy actually struck, usually by using long range fires from artillery, attack helicopters, and Multiple Launch Rocket Systems (MLRS) to delay, disrupt and attrit enemy formations at critical times. To do this, these commanders had to see far beyond the front lines, up to a hundred miles behind.

For most of the Cold War, the only ways to look that far behind the lines were either reconnaissance versions of fighter jets, or satellite imagery.  Reconnaissance jets could only see relatively small parts of the battlefield at one time, and were vulnerable to enemy air defenses. Satellites weren’t always overhead, and further, weren’t able to forward their information to the ground in a timely manner. Neither option had the ability to cover the vast space of a battlefield, nor the capability of observing that same space for hours at a time.

But if you could perch an airplane with long endurance up high enough on your side of the border, you could “peek over the fence” and watch the enemies movements for hours and hours. That was hardly a new idea. Observation balloons had been used as early as the Civil War for just this purpose. And the use of EC-121 and E-3 radar planes to look deep into enemy airspace had been around for decades. The problem was, looking deep into a wide swath of enemy territory meant having to use radar. And while radar was great for picking up planes flying around, trying to pick up targets on the ground was an entirely different challenge.

Radar of course uses the reflection of radio waves from objects to paint a picture. That’s great when you’re looking at the sky, and almost everything up there that reflects radar waves is of military interest. But when you start using radar to look at the ground, virtually everything reflects radar waves. Finding the reflections that represent items of interest is the challenge. It’s like finding a needle in a stack of needles.

By the early 1980s, technology had advanced enough to begin development of a system capable of finding those specific needles. Great leaps in computing power, the introduction of phased array radars, the development of techniques for signal processing for radar modes such as Moving Target Indicator (MTI) and Synthetic Aperture Radar (SAR) meant that an airborne radar system could be designed that could show militarily significant traffic on the ground. Secure data links meant that information could also be shared with stations on the ground.

In 1985, two prototype models, the E-8A, were built using converted 707s retired from airline service. Equipped with the APY-3 phased array radar, they were used to demonstrate the technology, find what worked and what didn’t, and explore what the “ultimate” configuration should be. After the Iraqi invasion of Kuwait in 1990, the Air Force deployed these test-bed aircraft in 1991. The results were excellent. The J-STARS were able to show Iraqi armored formations on the move, and could almost instantly call upon strike aircraft to pummel these formations.  Using the SAR radar mode, the J-STARS could paint a detailed picture of enemy positions such as surface to air missile sites and queue them for attack. In fact, if I recall correctly, the first use of the Army’s ATACMS missile system was in just such a scenario.

avjstars_3

J-STARS imagery of Iraqi forces fleeing Kuwait City along the “Highway of Death”- February 1991

The “Joint” part of the J-STARS was the data link from the aircraft to the Ground Station Module that allowed Army commanders to see the “take” from the E-8 in near real time. Further, the GSM could task the E-8 to “paint” targets of interest for more detailed observation. Thus, both a wide area surveillance and a fine grained picture of formations of interest could be accomplished nearly simultaneously. This gave both Air Force and Army commanders picture of the Iraqi disposition that would have been otherwise impossible. Using traffic analysis also allowed the commanders to make an educated guess as to the enemy intentions. When you know where someone is coming from, you can glean a fair idea of where he’s going. The GSM has been replaced by the similar, but updated Common Ground Station (CGS). Finally, laptop Common Work Stations have been fielded that allow lower level commanders to access the data from the J-STARS.

After several more years of development, the production variant, the E-8C entered service in 1996 . By 2005, the 17th and final production E-8C had been delivered, all equipped with the updated APY-7 radar.  All E-8 aircraft have been converted from Boeing 707s retired from airline service. As noted in the earlier post, the refueling over pressurization of one E-8C caused such damage that repair was not economically feasible.

Even though the original Cold War scenario of using the J-STARS against waves of Soviet armor as faded, new uses of the plane have been found. It still has great capability to track enemy forces on the ground. Traffic analysis from J-STARS has been used by Task Force ODIN in the counter-IED mission to predict likely locations for IEDs, and to attempt to back track hideouts for the bomb makers. A limited ability to track dismounted insurgents in Afghanistan has been discussed, but it is unclear just how viable this is. On  today’s network centric   battlefield, the E-8 also often serves as a key node of the network, much like a a server and router support your internet usage.  The J-STARS is also being developed for use in war-at-sea scenarios. With the recent strategic focus on Asia, this capability will be in much greater demand. The J-STARS has even demonstrated the ability to update targeting information of some stand-off weapons after they’ve been launched.

We’ve only got one real quibble with the J-STARS program. While the use of converted 707s made a great deal of sense, the decision to use the original JT3D/TF-33 engine seems a bit odd. At the same time the decision was made, the Air Force was in the midst of mounting new CFM56 high bypass turbofans on its entire fleet of KC-135 tankers. The CFM56 is far more fuel efficient, and has a great deal more power, which would allow E-8s to operate from shorter airfields, take off with more fuel, stay on station longer, loiter at higher altitudes (and thus extend the radar range), and share a common logistical pipeline with the KC-135 fleet. I’m sure there was a reason to stick with the older engines. I just don’t know that it was a good one.  Beginning in 2008, they have been equipped with JT-8D engines, which are surplus airline engines, cheap, and for which spares are plentiful.

1 thought on “Joint STARS”

  1. I don’t know if there is an advantage of the JT-8D over the CFM56 other than they’re relatively cheap. Pure turbjets are pretty rare on the ground these days, and most of those are in the flying relics from the 50s.

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