The Future Is Now for Army Radar
Foliage penetration is among the capabilities slated for airborne sensors.
Fiscal year 2015 marks the official kickoff of a U.S. Army program to develop a foliage-penetrating radar that will simultaneously locate still objects and track moving objects from a fast-moving fixed-wing aircraft. The next-generation system is designed specifically for jungle environments such as the Asia-Pacific region, South America and Africa, and by combining multiple capabilities onto one platform, it will allow the service to cut down the number of sensors currently needed.
The system does not yet have a great name, acknowledges Jonathan Corriveau, chief for the Radar and Intelligence, Surveillance and Reconnaissance Branch, Intelligence and Information Warfare Directorate, Communications-Electronics Research, Development and Engineering Center (CERDEC), Aberdeen Proving Ground, Maryland. For now, the system has been dubbed the Ground Moving Target Indicator/Foliage Penetration (GMTI-F). “It’s a very descriptive name on our end. GMTI/F means a lot to us,” Corriveau admits.
The U.S. military uses two primary categories of radar—GMTI, for tracking moving objects and synthetic aperture radar (SAR) for locating still objects. “With a synthetic aperture radar, you’re able to do large, wide area detections,” says Kim Koch, CERDEC’s counter concealment team lead. “When you look out through a camera lens, you can see a little bit, but these radars can do very wide area scanning. They’re able to pick up from long ranges. I think of that as a pizza slice on the ground.”
High frequency radars can switch from SAR mode to GMTI mode and back again. They penetrate clouds, dust and certain other atmospheric effects very well. And high frequency systems are effective on fast-moving airplanes. But the higher frequency systems have a major drawback for jungle warfare. “When you get to things like structures and foliage and things that are more substantial, the higher frequency-type radars that we work with aren’t particularly good at that,” Corriveau says.
So, for foliage penetration, the Army uses low frequency systems down around the 400-megahertz range. But those low frequency systems work best when mounted on slow-moving or hovering platforms, such as helicopters and aerostats. “The physics are a little bit different at the lower end of the frequency band,” Corriveau says.
Koch uses an analogy to simplify the difference. “When I think of the high frequency radar, I think of it like a penknife. A penknife cannot go through a tree or foliage. When I think of low frequency radars, I think of a machete or a chain saw. It goes right through the foliage, right through the trees,” Koch says.
With the GMTI/F system, Army officials intend to combine the best capabilities of existing systems. “This system will bring in both the SAR function of a low frequency radar and the GMTI function of a low frequency radar, and it will put them together on a moving, fixed-wing platform, on an airplane,” Corriveau says. “It’s never really been demonstrated on an airplane, something moving very quickly. We want to put it all into one package.”
So, while GMTI/F may not yet have a cool name, it is expected to do cool things. “This will also allow us to simultaneously track stationary objects as well as moving objects all at one time,” Koch states. The Army’s future is going to a multi-intelligence platform rather than multiple platforms for differing missions, she points out. “The future is to combine many different intelligence assets into one platform. This next-generation system allows that to go forward.”
The program also might add capabilities not available on current radar systems. In some cases, capabilities dreamed of years ago may be possible now with more advanced technologies, such as more powerful processors. Corriveau cites a multi-input/multi-output feature commonly referred to as MIMO. It uses smart antenna technology to allow multiple antennas at both the receiver and the transmitter to improve efficiency and effectiveness. “When you’re transmitting a lot at once, and you’re receiving a lot at once, there’s a lot to look at, a lot to parse through and process,” Corriveau says. “Now, it’s starting to be applied in a lot of places in the communications industry. It is just starting to be used now on some radar applications. That is something we’re going to pursue.”
One of the first phases of the program will be to explore those theoretical concepts and decide which are the most promising, he adds. “Then, we’ll spend the next couple of years proving those out and whichever ones we choose, reduce risk on those, prove them out and then build a prototype system,” he reveals.
One of the biggest challenges, Corriveau reports, will be filtering out the clutter that lower-band radars tend to pick up. “When a lot of things are moving, you only want to see the things that you’re interested in. I don’t care that the trees are blowing in the wind or that there are animals running around on the ground. I’m looking for something very specific, so to find and to pull out the actual moving targets is very difficult. The lower the frequency, the harder this becomes, but of course the lower the frequency, the more penetration capability you have,” he says. “That’s going to be a very big problem. We’ve looked at it from a mathematical, physics-type problem, but in some cases, it’s not practical, so we’ve had to come up with some advanced techniques that make it more applicable, more practical.”
The final solution likely will encompass hardware, software and everything in between. “It’s everything. It’s algorithms. It’s hardware. It’s a lot of different aspects,” he says. “It’s doing things we haven’t done before. Theory tells us it can be done, but it hasn’t been done before.”
The GMTI/F research and development program is expected to last five or six years, a contrast to the shorter-term, rapid deployment environment of recent years. “This is more of a longer-term technology quest. A lot of things we’ve done in the past—especially with the wars going on—have been driven by how fast we can get it out there,” Corriveau observes. Once the technology is developed, the plan is to transition it to the Program Executive Office-Intelligence, Electronic Warfare and Sensors “to productize it, package it, and make it deployable so that it can be used in a live mission,” he adds.
GMTI/F builds upon several predecessor programs. CERDEC partnered with the Defense Advanced Research Projects Agency (DARPA) in the 1990s on a foliage-penetrating, synthetic aperture radar system known as FOPEN SAR. CERDEC followed that with an in-house program to develop the Tactical Reconnaissance and Counter-Concealment-Enabled Radar (TRACER), which was developed with Lockheed Martin.
TRACER has been deployed to U.S. Southern Command, where it is used for counter-terrorism, humanitarian and disaster relief operations. “TRACER is a current system that is deployed and that is useful to the warfighter,” Corriveau indicates.
CERDEC also worked with DARPA on the Foliage Penetration Reconnaissance, Surveillance, Tracking and Engagement Radar (FORESTER). The sensor is designed to detect and track dismounted soldiers and vehicles at a range of about 20 miles and also can locate and track people in the open or through light foliage at a range of at least 30 miles. “We’re going to move up from FORESTER. “We’re going to get this GMTI capability, and it’s going to work on Army inventory fixed-wing platforms and also pull in the SAR mission. We’re looking at that as the future of foliage penetration so that we have one sensor that does everything we need it to,” Corriveau says.
He adds that with the new fiscal year, his team is itching to get underway. “Now that we’ve envisioned these ideas, we have to go act on them and see how they work,” he says.