Far from being an antique curiosity of World War II, radar technology today has become smaller, cheaper, easier to manufacture, and more powerful.
Modern radars can look beneath the Egyptian desert from an orbiting spacecraft and see ancient riverbeds and ruins. From miles away, they can peer through clouds or fog to figure out what a ship at dock looks like by sensing patterns from its rocking motion. They soar overhead in small, unmanned planes to give military commanders a live picture of a battlefield in any weather, day or night.
Yet the most surprising accomplishment of this military-driven technology may be its steady move into civilian life. Already, people barely notice when radar calls a fault at tennis tournaments or delivers a more accurate weather forecast. So hold onto your radar detectors, scientists say.
There's much more to come as military breakthroughs spark creative new ideas for civilian use - from making seven-day forecasts as accurate as today's two-day predictions to building cars that warn lane-changing drivers of a car they can't see.
In the military, radar remains the backbone of America's missile-defense system.
"[Radar] does everything from large-scale surveillance to identifying a specific threatening object and actually guiding the kill-vehicle [missile] to it," says Rick Yuse, vice president of the missile-defense program at Raytheon, a major US defense contractor.
Today's technology is allowing powerful radars to be built that would have been unimaginable to scientists who built giant radar towers in the late 1930s to defend Britain's coastline.
But while giant missile-defense radars, such as the BMEWS systems, may mushroom to 10 or 12 stories tall, much of the most exciting research in radar is thinking small.
Just coming on line for aircraft, for example, is Active Electronically Scanned Array (AESA) radar, a fully electronic radar with no mechanical moving parts that can track many targets and guide missiles to those targets simultaneously. It is operating on just 18 US Air Force F-15s. There are plans to equip 161 more F-15s and other military aircraft in the future.
AESA is "stealthier" and more reliable than older radars and may eventually be put to use helping to intercept cruise missiles. Some evidence suggests it is powerful enough to knock out ground-based radars if its beam is concentrated on a narrow spot. That task, though, is expected to be handled mostly by the military's new Thor radar-jamming system, expected to be available in 2008.
Another radar in the works, the mini-SAR, has gained tremendous attention in recent months. Synthetic aperture radar (SAR), often called "imaging radar" because of its ability to show stationary objects with almost photographic clarity, has been used in reconnaissance aircraft like the U-2 for years. Now scientists at Sandia National Laboratories in Albuquerque, N.M., are miniaturizing it to fit into the tiny unmanned Shadow aerial vehicle, not much bigger than a model airplane.
SAR images are nothing like the smears of light seen on early radar screens. With a miniSAR, weighing less than 30 pounds, the Shadow could distinguish two Coke cans standing only inches apart from several miles away, says George Sloan, the miniSAR project leader at Sandia. And many radar images must be interpreted by an image analyst. Not so with SAR, Mr. Sloan says. That means troops can view images themselves and act quickly.
"I can show these images to my 10-year-old son, and he'll be able to identify a car, a truck, a building, or whatever," Sloan says.
The group hopes to flight test the miniSAR in early 2005.
Eventually, Sloan says, the miniSARs might be small enough, and cheap enough, to be put inside precision-guided bombs, for use when guidance systems such as GPS are not practical or are being jammed.
But no matter how much radar is doing now, military planners want it to do more.
One of the great interests today is in a radar system that can see through foliage, which can be used to hide enemy positions, says Doc Dougherty, chief scientist at Raytheon's Space and Airborne Systems in El Segundo, Calif. He calls it a "very hard problem" to solve.
Others see great potential in space-based radars on satellites, which could fill in the information gaps other radars miss. And Sandia is also working on radar "tags" that could be mounted on military vehicles, and perhaps eventually attached to every soldier, to identify them as "friendly" forces when they are tracked by their own radars, cutting down on fatalities from friendly fire.
A number of challenges remain, including cutting the cost and preventing enemy forces from disabling, employing, or imitating the sensors.
Meanwhile, in the civilian realm, automakers are exploring radar as the next big thing in safety.
Toyota is putting a radar-based precollision system into its Lexus LS430 luxury sedan. A split second after the onboard radar detects an imminent collision, the car tightens the seat belts around passengers and begins braking.
By the 2007 model year, at least one major carmaker also will be using radar to help drivers change lanes safely, says Scott Pyles, a spokesman for Valeo Raytheon Systems in Auburn Hills, Mich., which is manufacturing the device.
It's based on phased-array radars developed for the military. The unit is mounted in the rear of the car beneath the surface, making it immune to damage from rain, salt, snow, or ice.
Side collisions, caused when drivers fail to see another vehicle in their "blind spot" during a lane change, account for more than 413,000 auto accidents per year and injure more than 160,000 people, Mr. Pyles says. When the Valeo system detects another vehicle or a pedestrian in the driver's blind spot, it activates a LED warning display on the driver's side-view mirror.
"It's a very reliable technology, and you can use it in all weather," he says. He expects "you'll see the price in the $500 to $600 range" or as part of luxury-option packages. The same technology could also be used to provide assistance in backing up and parking, he says.
Further down the road, "long-range" radar may be used to determine the speed of approaching vehicles for situations such as merging into freeway traffic or judging whether a turn across traffic can be made safely. And it's beginning to be used to monitor traffic on freeways, giving traffic planners a real-time view of the number of vehicles, congestion, average speeds, even the sizes of vehicles on the road. Radar's reliability and ability to "see" in any weather make it an attractive alternative to video cameras.
Radar already has brought huge improvements to weather forecasting. Now its newer cousin, "lidar," which uses laser light instead of radio waves, may make even more accurate predictions possible. Unlike radar, lidar has the ability to measure winds without any particulates, such as water vapor, making it able to track so-called clear air.
"Measuring upper atmospheric winds is the No. 1 missing ingredient for making long-term weather forecasts," says Peter Tchoryk, executive vice president of Michigan Aerospace Corporation in Ann Arbor, which is developing a lidar system for doing just that.
With funds from the National Oceanic and Atmospheric Administration, Mr. Tchoryk's company has built ground stations in New Hampshire and Hawaii to test the lidar weather-tracking system. The next step is to launch a high-altitude balloon with lidar to 100,000 feet, a final test before putting the weather tracker into a spacecraft.
From there, it could monitor movements of large weather systems and predict their wind flows.
As a result, seven-day weather forecasts would be just as accurate as today's two-day forecasts.
"It has long-term impacts in terms of agriculture [and] storm and hurricane prediction," Tchoryk says, "not to mention the military aspects of being able to forecast winds."
Lidar is also being used by law- enforcement officers to track speeders on busy highways, where its focused beam lets it easily pick out individual vehicles.