There have now been 89 incidents recorded in France of mini- or micro-UAVs being deliberately flown over sensitive areas. In 27 cases, legal action is being taken against those alleged to be responsible. So it’s not just an isolated problem, typified by the well-publicized flyovers of the Élysée Palace and French nuclear powerplants. This week at the Paris Air Show, the French company is highlighting its approach to countering these malicious flights with four scenarios, and a movie.

“There’s no single solution, and the methods must not be expensive. We must be smart and capitalize on existing sensors, communications networks and effectors,” said Jean-Michel Negret, the company’s project officer for small UAS and C4I. Thales realizes that the threat is posed by a very diverse set of micro-UAS that are available. But they share one characteristic–very low signatures, be it visual, thermal, acoustic or electromagnetic.

Furthermore, not all of the means available to counter this class of UAVs are usable. “Neutralization is tricky, especially in an urban environment, and because political decisions are needed,” noted Pierreck Lerey, strategy and marketing director for UAS and ISR.

Thales is part of a public-private partnership of seven French entities that are participating in an 18-month study, Project Angelas, on combating non-cooperative UAVs. Dominique Poulin, of the French aerospace laboratory ONERA, which is leading the project, said that potential end-users include the Gendarmerie Nationale and the Paris Police, as well as the armed forces.

Poulin said passive radar is a promising detection technology, especially to discriminate against false targets such as a flock of birds. Then, for identification, 3-D laser imaging might be used. Following this comes classification and neutralization.

Thales is also studying how its existing radar air defense radars such as the GroundMaster 200 might be adapted to the detection task by adjusting the software that previously rejected such small targets.

Lerey said that passive direction-finding could be used to find the “pilot” of the threatening mini-UAV–essentially by adapting GPS tracking techniques from the cellphone world.

Thales is developing a user-friendly C2 software for analysis named Clearland. There must always be an operator in the loop, he added. This is one of three work packages within Project Angelas that Thales is leading. The others are the used of electromagnetic sensors for neutralization. Poulin said that jamming had been proven recently, but using lasers to shoot down the errant UAVs might be unacceptable.

Jean-Philippe Hardange, working on strategy and operations at the Thales air defense radar site at Limours, agreed with Poulin that passive radar techniques are now mature enough to aid the task. The company took out its first patent on exploiting FM signals as long ago as 1995, and has since enjoyed funding by the EU and the French MoD to develop prototypes for civil and defense applications using digital TV signals. A new ground-surveillance radar developed at Limours, named Squire, would be a good candidate as a detection system, because it is low-cost.

As for neutralization, Hardange showed eight options, some of them more relevant to larger UAVs. They include conventional anti-aircraft guns, lasers, GPS jamming, directed energy and hijacking of the UAV’s command and control datalink. The platform for some of these effectors might be airborne–perhaps a “blue force” UAV defending the required area. Prediction of the debris field resulting from a UAV kill is just as important, especially in urban areas, he added.

“Essentially, we’re talking about the same functions and constraints as in the conventional air defense mission,” Hardange continued, “but we must now adapt and fill the gaps.”