France's Unique Horizon

by Michael Puttré
Aug. 1, 2003

The main question about the French Army's Horizon helicopter is: What's it for?

Some background. The Horizon - Helicopter Observation and Radar Investigation of Zone - was developed during the Cold War as a sensor for assisting artillery in identifying vehicle targets to engage. The platform is a Eurocopter AS 532UL Cougar helicopter. Four of these aircraft plus two ground stations are organized as the Horizon Squadron, which is attached to the 1st Combat Helicopter Regiment based in Phalsbourg, Lorraine.

The operative sensor is the Thales (Paris, France) Target radar, which is a J-band multimode radar, with its primary mode being a moving-target indicator (MTI). Its range is described as about 100 miles at a resolution of 10 meters and a target velocity between about 5-170 mph. A combination of mechanical and electronic scanning enables it to cover nearly 8,000 square miles in 10 seconds. The French Army officers and specialists of the Horizon Squadron described it with pride as the "best [MTI] radar in NATO" with respect to its resolution and reliability.

The radar's purpose is to detect moving vehicles, and it can classify targets as tracked vehicles, wheeled vehicles, low-flying helicopters, or boats. The helicopter hovers at an altitude between 8,000-15,000 ft. while it performs this mission. The crew of four includes two pilots, a flight engineer, and radar operator. The system has a Thales Agatha microwave datalink that connects to a dedicated ground station, which is mounted in a truck. The ground station, in turn, would be in communication with the appropriate command echelon. Currently, the ground station is in communication with the theater's Joint Operations Center, although it could be delegated to lower headquarters on an as-needed basis. The French describe their decision cycle as sensor-to-commander-to-shooter, saying that they are willing to tolerate a delay in order to verify targets. "An experienced officer in the ground station passes information along with comment [his emphasis] to the JOC," said one Horizon Squadron officer.

This process is not necessarily cumbersome. During Operation Strong Resolve, a NATO exercise in Norway the first two weeks of March 2002, the Horizon Squadron deployed two helicopters and two ground stations with the goal of assisting in the destruction of an enemy force. That force was considered destroyed within three minutes of its detection.

Which brings us back to the original question. Over time, budget constraints and the requirements of the French Army have moved the Horizon into a role described as a theater asset. This says more about the scarcity of the systems than about its stature in a theater of operations. Due to the weight of the radar, the Cougar is not able to take off with a full load of fuel, so its endurance is limited to three hours, including transit. Operationally, a given helicopter would be tasked with monitoring a tightly defined area - a crossroads, valley, or landing beach - where enemy activity is expected. The squadron's aircraft would provide coverage of the sector in relays. A single Horizon Squadron - and there is only one - is not capable of theater-wide coverage, as is a US E-8C J-STARS aircraft. While the Horizon might have a more accurate MTI, the J-STARS can cover more ground. Is there a way for the two to work together?

In fact, Horizon officers consider it essential that their helicopter's MTI be combined with other sensors, including J-STARS. The J-STARS detects a possible enemy convoy at long range, and it tasks Horizon to move in for a closer look. Horizon, in turn, might cue other intelligence, surveillance, and reconnaissance (ISR) assets, such as unmanned aerial vehicles (UAVs). This sort of multi-sensor approach to ISR, called "cross-cueing," is certainly the future of the electronic battlespace. When the Horizon Squadron deployed to Skopje, Macedonia, in support of NATO operations in Kosovo, it acted in concert with other reconnaissance assets.

But realistically, four helicopters and two ground stations are not sufficient to embark on a sustained campaign. No theater commander is going to build a plan based on such scant resources. While he might be able to incorporate the Horizon Squadron into his plan, the risk of a mechanical failure, combat loss, or other event taking even one helicopter out of action would seriously degrade the unit's operational capabilities. Budget permitting, the squadron wants to expand to four helicopters. It plans to operate its Cougars until 2020, when NH90 helicopters might be made available to the unit. "The Americans have to manage resources," said one French observer. "The French have to manage rarety."

Less and Less

Tacitly, members of the Horizon Squadron acknowledge that their limited number of helicopters and ground stations seriously limits their operational capabilities. Some of this limitation is by design. The French Army has not embraced the Horizon for its own forces, and so its original purpose of serving as a targeting-support sensor for the artillery is all but forgotten. It is seen as an asset that fulfills certain NATO requirements, as expressed in exercises such as Strong Resolve and even operational missions such as in Kosovo, and the French Army seems content to operate the Horizon in the context of specialized missions for joint operations with NATO.

The Horizon is the French Army's first airborne radar. It descended from a program called Orchidée, where essentially the same MTI radar was mounted in a Super Puma (Cougar) helicopter, but with the addition of a direct datalink to enable J-STARS interoperability. The French Army evaluated Orchidée in the late 1980s but cancelled the program in 1990. Nevertheless, the occasion of the 1991 Gulf War prompted France to send the prototype to Saudi Arabia. During the war, the aircraft performed a number of MTI spotting missions for US Army AH-64 Apache helicopters and for Jaguars and Mirages of the French Air Force. The experience was positive enough for the French Army to order the Horizon, which represented a simplified configuration with fewer ground-station components and no J-STARS interoperability. An initial requirement for six was eventually cut to four.

Although simplified from its earlier incarnation, Horizon has benefited from developments in C4 I [command, control, communications, computers, and intelligence] technology and procedures over the last decade. In addition to its datalink to the ground station, the helicopter has an encrypted VHF radio for voice communications and an IFF system to enable it to operate safely at high altitudes in busy airspace. It has both GPS and inertial navigation. Data processing allows its radar receiver to function as an electronic-support-measures (ESM) system. There is some discussion about adding a synthetic-aperture-radar (SAR) capability in the future, although it is not clear if the platform would support it. Issues of weight and antenna interference would have to be resolved. More immediately, though, an upgrade is planned to reduce weight and thereby enable the Horizon to remain on station for three hours, plus transit.

Each Horizon helicopter is fully outfitted for battlefield deployment. The radar's antenna has very low side-lobes and frequency agility for resistance to electronic countermeasures, including anti-radar missiles. The electronic- warfare suite consists of a Thales (Paris, France) Fruit radar-warning receiver and Damien missile-approach-warning system, along with MBDA (Paris, France) Saphir countermeasures dispensers. In addition, the Horizon has a de-icing system that enables it to operate in clouds, thus reducing its visibility.

The limitations of using a battlefield helicopter as a ground-surveillance-radar platform could give rise to the question: So why not use a plane? Horizon Squadron officers say that a helicopter offers the advantage of discreet deployment to a theater. In addition, a navalized version of the helicopter is under consideration, along with a shipboard version of the ground station. More importantly, a helicopter platform provides the opportunity to monitor a given sector with a sensor with a high resolution. And it is worth considering that land forces have a lot of experience working in concert with helicopters. The comfort factor is not to be overlooked.

The Horizon Squadron has demonstrated that it is capable of integrating usefully into exercises and combat operations in far-flung theaters. Moreover, it has enabled French commanders to explore how they want to develop joint operations involving multiple, cross-cueing sensors. The experience of the Horizon Squadron is likely to prove valuable in air-land battles of the future.