Defense Technology International - October 2007 - (Page 32) DISPATCHES GLOBAL YOU’RE ON THE AIR Passive radar uses FM signals to defeat stealth JORIS JANSSEN LOK•LIMOURS, FRANCE hales Air Systems has been gathering operational experience with its new Homeland Alerter 100 passive surveillance radar—including use at a recent NATO live-flying exercise. The HA 100 discreetly receives and processes signals transmitted by commercial FM radio stations and reflected by aircraft, to compile an air picture to a range of more than 100 km. (62 mi.). One benefit to the long wavelength of FM signals in use by the HA 100 is that stealth features cannot hide an aircraft or missile if it is bigger than 1 meter (3.3 ft.), says Jean-Philippe Hardange, vice president of strategy, technology and innovation for Thales. “We just listen to the radio,” Hardange quips. The first prototype of the HA 100 was sold to the French procurement agency DGA in late 2005, and delivered to the air force last November for trials. The operational evaluation is due to end in October. The HA 100 was deployed at Cazaux air base in the relatively flat southwest of France, in the hilly area of the Rhone River valley, where it was operated close to industrial parks, and at Villacoublay air base in Paris, an urban setting. A second HA 100 system, procured by Norway for trials, started operational evaluation with the participation of engineers from the French air force and Thales in “Bold Avenger 2007,” NATO’s largest live-flying exercise this year, which took place in September at Orland air base near Trondheim. Hardange says Norway’s interest in the radar pushed Thales to more than double the range of the HA 100 sensor from its original 50 km. “Radar engineers from Norway’s FFI defense research establishment pointed out that the physics of the technology al32 THALES AIR SYSTEMS T low a range extension. We had a surplus capacity in signal processing in the prototype, so we upgraded the range.” The HA 100 has the biggest signalprocessing capacity of any Thales-built radar—twice that of the previous capacity leader, the Herakles S-band naval multifunction radar. Hardange says a third HA 100 system has been sold to the European Union’s Sixth Framework Program for Research and Technological Development. “This is to assess the use of passive radar in air-tra c management. Two trials are Thales HA 100 passive air-surveillance radar is deployed during a field test. The white van holds the electronics for the sensor. planned, one at Frankfurt-Main Airport in Germany, and one at Brno Airport in the Czech Republic, where the HA 100 will be used like a primary radar.” Interest from other customers is mounting, Hardange says, including “NATO nations and Asian nations.” The main competitor is Lockheed Martin’s Silent Sentry, says marketing director Veronika Roux. Development of passive radar is ongoing in several areas, but she says the HA 100 is “one of the few that can be proposed as an operational, ready-to-use sensor.” One application is to use the sensor as a discreet gap-filler to complete the air picture at very low level, when the location of a high-profile target has to be protected against air attack. Each of the three HA 100s built so far is installed in a white Renault van so as not to attract attention. In the rear of the vehicle is the receiver electronics rack. The cooling machinery is in a separate compartment, while forward is a rack with the signal-processing hardware, based on Hewlett Packard PC processors. A twin ethernet cable hookup is installed on the left side of the vehicle aft, through which the HA 100 links to a wider air-defense or air-tra c control network. The antenna, located on a deployable mast, has eight dipoles arranged in a circle. Hardange says the sensor works with signals from up to eight FM radio transmitters. The processing algorithms first construct a “very pure” reference image, then detect and track signals reflected by targets, which means “canceling out unwanted reflections from buildings and other clutter.” The HA 100 has a 1-sec. update rate, so not just slow-flying aircraft but targets flying tactically at higher speeds can be detected and tracked—all on the strength of exploiting the FM radio waves transmitted by towers and reflected by the targets. The HA 100 is part of the new Alerter family of active and passive FM and low-band UHF surveillance radars from Thales. Other members are the GA 10 Ground Alerter, with a range of 10 km. (designed as an anti-mortar alert radar), and the GA 1, a foliage-penetrating radar with range of 1 km. It is offered by Thales and DRS Technologies for U.S. border surveillance of densely forested areas along the Canadian border. I www.aviationweek.com/dti DEFENSE TECHNOLOGY INTERNATIONAL OCTOBER 2007 http://www.aviationweek.com/dti
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