Eleven years ago this month, when terrorists attacked the USS Cole as it was refueling in Aden Harbor in Yemen, sailors had little time to react before the attackers’ small boat rammed into their warship. It blew a 40- by 60-foot hole in the ship’s side and killed 17 members of the crew.
Could a better radar have saved some of those lives?
The recent, successful test of a local company’s radar technology could lead to better data about the behavior of fast-moving weapons on the battlefield and help the military develop stronger defenses against various forms of attack.
In September, Cambridge Consultants released the results of Navy trials of its holographic radar system. Emitting a constant stream of radio waves in every direction at once, rather than a narrow beam that scans a piece of the sky in time with a rotating dish, the system gives observers a level of precision and detail far beyond that of conventional radar, said Gary Kemp, program director for the British company, which has its US headquarters in Cambridge.
Conventional radar monitors a target less than 1 percent of the time as it scans the skies, said a company statement. Using so-called holographic radar, which creates a three-dimensional bubble of radio waves, Cambridge Consultants’ Land and Surface Target Scorer was able to track, in real time, five-inch shells shot from a ship at a target on the water’s surface, the company said. The shells traveled about 1,000 miles an hour.
With conventional radar, “if an object moves lightly in between scans, then there will be information that you are not getting that may help you distinguish that object,’’ Kemp said. “A holographic radar stares into a whole volume of space without scanning. It doesn’t scan a narrow beam. It has a very broad beam.’’
What’s more, radio wave reflections from clutter like waves and other obstructions make conventional radar useless for tracking a projectile like a shell near the water, Kemp said. The holographic radar, however, can see it.
“You can extrapolate [its position] from all of the signals that are producing the three-dimensional map of that volume of space,’’ he said.
The Navy is using the system to prepare sailors for attacks against warships like the one against the USS Cole, Kemp said. The service plans to mount the system on speedboats that can serve as targets for shooting practice, with the radar measuring the accuracy of the gunners’ shots, he said.
Holographic radar isn’t new. Receiving and deciphering the massive amounts of data it produces to create an accurate picture of reality, however, is a breakthrough.
“Implementing this in hardware and having the processing to carry it out - that integration is fairly recent,’’ said David Castañón, a professor in Boston University’s Department of Electrical and Computer Engineering. “You needed the software to catch up with the performance.’’
Kemp declined to describe the inner workings of the system. But geophysicist Tim Bechtel, a professor at Franklin & Marshall College in Pennsylvania, said Cambridge Consultants’ system probably used the Doppler effect to distinguish fast-moving objects, like artillery shells, from distractions like explosions or sea spray.
The Doppler effect describes a radio wave’s change in frequency as an object moves in relation to another object. People experience the Doppler effect with sound waves when they’re standing next to a train track and a locomotive passes. Even if they close their eyes, they can approximate the train’s location by its sound, which changes pitch as the locomotive approaches, then travels away from the listener.
“The brilliance here is using the Doppler effect to calculate the trajectory,’’ said Bechtel, whose research includes developing holographic radar devices designed to detect land mines and archeological sites underground. “The Doppler effect pulls the target out of a background.’’
Kemp acknowledged the system is not yet advanced enough to supplant conventional radars at airports or those used throughout the Navy. But Cambridge Consultants’ technicians were already envisioning using it to help helicopter pilots see the topography of landing zones when visibility is low. Conventional radar would simply bounce back from the ground without providing a useful picture of the land, he said, but the company’s system would be able to distinguish between divots, slopes, trees, and vehicles.
“How do you land a helicopter in a dust storm?’’ Kemp asked. “Helicopters create their own dust storms when they land, especially in these current battle zones. You can be 200 feet above the ground, and there is zero visibility. That’s called a brownout. What pilots needs is a virtual view of the ground beneath them.’’
Castañón speculated that the system might someday allow American warships to track and pinpoint enemy ships that, in an age of terror, might conceal themselves as innocent civilians.
“Think of a Navy ship in the Mediterranean right now,’’ he said. “There are going to be small boats operating within miles of where you are, because that’s where they fish.
“If they happen to have guns and shoot at you, you’re not going to stop the shells, but if you detect the trajectory, then you know where it came from. You know you’re being attacked, so you can get rid of the boat where it’s coming from.’’