The drones ears and eyes.

The role of drones is increasingly expanding into that of manned aircraft territory. Initially relegated to simple recce duties, they are now moving into synthetic aperture radar, singint, personnel support and weapon delivery missions. Some of these missions were only reserved for the larger models, but with the miniaturisation of payloads, the boundaries separating weight and mission categories are blurring.

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Drones, apart from the target variety, are almost synonymous with reconnaissance, and their modern history (as opposed to World War Two era) can be traced back to the Vietnam War years. At the time their average life there was a mere 3.5 missions. And they were huge (a Ryan 147H had a wingspan of almost ten metres) for comparatively moderate duration missions, were launched by a Hercules (then DC-130) and had to be recovered through 'mid-air snatch' methods by helicopters. Timid inroads into communications intelligence (comint), however, also started in the late 1960s.

Electronic Intelligence

Unless earlier black programmes have successfully managed to remain very dark to date, what probably sparked off the use of unmanned aircraft for electronic information gathering is the loss of a US Air Force EC-121 (a Super Constellation) on a comint mission with 31 men aboard in June 1969 off the coast of Northern Korea. The mission also entailed detecting the mission frequency of the anti-aircraft missile bases. This paved the way for the development of the turbojet-powered Ryan 147TE which was able to intercept North Korean, Chinese and Russian communication and radar emissions from a distance of up to 1000 kilometres and relay them to American ground stations based in South Korea. With the end of the Vietnam War, the use of jet-powered drones started to fall out of favour, including for recce missions, although they had been heavily used by both Israel and Egypt in the wake of the Six-Day War. Incidentally, Ryan, designer of Lindberg's Spirit of Saint Louis, became Teledyne Ryan and eventually came under the banner of Northrop Grumman.

In the meantime, electronics shrank in size (even more dramatically in recent years), something that went along with much lower power requirements. Given the size of its territory, Israel did not need extremely long-range drones to meet its needs and soon all equipment was able to fit in what looked like large radio-controlled aircraft. For years the drone idea was not looked upon too seriously by other nations, but now they all want them. IAI, Elbit and Elisra quickly became a sine qua non in the field (incidentally, IAI now stands for Israel Aerospace Industries, where Aerospace replaces Aircraft).

Elisra, for example, produces the AES-210V. This esm/elint system, which is mainly composed of two flat sensors and a computer, detects, identifies and locates both airborne and ship-based radars. It achieves fine direction finding with an advanced digital phase interferometer and offers a Windows NT manmachine interface.

The most recent development in the field of drone-carried elint systems is the Euro Hawk, for which EuroHawk (in one word), a company equally shared by Northrop Grumman and Eads, received a 430 million [euro] contract in February. Approved by the German government's budget committee, the Euro Hawk (seen in our title illustration) is aimed at providing the German Air Force with the means to carry out reconnaissance missions once its Breguet Atlantics, in service since 1972, are retired from service. The Euro Hawk airframe is based on the Northrop Grumman equivalent of the RQ-4 Block 20 Global Hawk operated by the US Air Force, but will carry a sigint payload developed by Eads. The package will be able to perform both elint (detection of radars) and comint. The contract includes the integration of the suite into one aircraft, the development of the ground infrastructure and delivery of the demonstrator by 2010. Another four aircraft are planned for delivery between 2011 and 2014. Thus equipped, the German Air Force will be able to conduct 30-hour wide-area missions from altitudes of up to 60,000 feet. The maximum speed of the Euro Hawk is 550 km/hour.

Interestingly, a year before the German Government award to EuroHawk, Northrop Grumman announced that its Asip signals intelligence payload had taken to the air aboard a U-2, indicating that a << Global Hawk variant of the Asip sensor will complete flight testing in 2008 and begin production in 2009 with operational fielding expected in late 2011 >>. Three Asip packages are being test-flown by the U-2 with operational fielding planned for 2008. Thus far, the Global Hawk was essentially developed to perform image intelligence missions based on imagery derived from its electro-optical and synthetic aperture radar sensors.

IAI and its Elta division regularly display their recent capabilities in terms of electronic warfare systems. Seeing these payloads on a stand it is always difficult to visualise where they would fit on a drone. At the recent Euronaval exhibition near Paris, IAI's stand was being watched by a Pioneer mock-up hanging from the ceiling on which one could spot a number of the sensors that the visitor could see scattered around the stand. For instance, the EL/L 8385 is an Elint system that is described as being able to cope with the challenges of modern dense radar environments, and sure enough, when looking up, one could easily spot its emplacement on both sides of the aircraft's nose. Another system, which almost seems to pair with the aforementioned, is the EL/K-7071. In fact, it performs the same task, but as a comint package: instead of monitoring radar signals it scans the air to catch and classify communication signals, including those with frequently changing parameters.

There are basically two ways of obtaining images. The first is to use optical devices (whether television or thermal) or electromagnetic sensors (radar), and in some instance, these are combined, as on the Northrop Grumman Global Hawk.

In the case of optical devices, the extraordinary progress in the development of high-resolution and high-sensitivity sensors has enabled such belly-mounted turrets to provide images of astonishing quality, although their manufacturers are not cleared to provide actual data regarding ranges. In most cases, the range from which footage shown at exhibitions were taken is unfortunately not disclosed. However, the quality of the sensors is not the only key parameter leading to image quality. The other factor is stabilisation. Stabilisation is used to keep the camera locked into the aimed position while the aircraft is allowed to move ahead, turn, climb and swing, and it also 'erases' all the other minute motions resulting from vibrations and sharp bounces of the platform. Clearly the enemy here is inertia. Again, miniaturisation (and therefore lighter weights) have greatly helped solve stabilisation problems, but the smaller size also helped manufacturers to locate the individual component's centre of gravity as close as possible to the axes of the gimbal assembly to reduce cantilever and inertia effects as much as possible. Another technique that comes to the rescue is an image stabilisation system similar to those that we now see appearing on commercial single-lens digital cameras.

Typically, and according to various manufacturer specification sheets, turret stabilisation accuracy ranges between 1 and 30 [micro]radian. Because this accuracy comes with a cost, the final choice will depend on the type of mission an aircraft will have to fly: the longer the target range, the more accurate the stabilisation.

Cost will also depend on what the turret contains. Day camera, infrared, laser rangefinder, laser illuminator, inertial navigation with integrated GPS receiver. Some include all of these amenities.

Manufacturers

Turning to thermal imager manufacturers, there is little doubt that one of the most prolific is Flir Systems. Asked to provide examples of unmanned vehicles (including ground vehicles) that carry Flir turrets, the manufacturer provided this list: Raven B, Dragon Eye, Global Hawk, Pointer, Scan Eagle, Silver Fox, iRobot, Aerosonde, Desert Hawk, Puma, Bat, Swift, Evolution, Airfoil, Helicam, Packbot, RMax, Neptune and Talon. In fact, according to a company official, << Flir has supplied more flir imagers to the UAV community than all other manufacturers combined >> in 2006.

Part of this success is owed to the company's Micron and Photon miniature cameras. Originally developed by Indigo Systems (which eventually came under the fold of Flir Systems) as the Omega, the Micron had been adopted as an optional infrared sensor for the Aerovironment Raven-A drone and for the Dragon Eye, the latter having been acquired by the US Marine Corps in 2003. Given the popularity of the Raven-A, the US Army decided to order an improved version of the bird under FY2006 funding as part of its Small Unmanned Aerial Vehicle programme. Flir's Photon, offering higher resolution and ruggedness for a lower cost, was adopted for the purpose, resulting in Flir supplying more than 5000 cameras of both types for the Ravens and Dragon Eyes only. For 2007, Flir announced that it had been awarded a $7.3 million contract to deliver Photons for the Raven-B.

The Photon is promised a long future as, apart from small drone applications and its adoption for other platforms such as the US Marine Corp's Advanced Ceramics Silver Fox and the Navy's DRS Neptune and by other manufacturers, it is now also being used for integration into small gimballed systems. One of the reasons behind this, according to Flir, is that the Photon is, << nearly identical in height and width to the so-called 'block cameras' used for daytime imaging applications >>.

Given the incredibly high number of drone manufacturers--small and large aircraft included--those who manufacture both their own aircraft and electro-optical sensor systems are few and far between. The ones that spring to mind are Sagem, Denel, Elbit and now General Atomics. The latter, it must be added, also produces its own synthetic aperture radar-ground moving target indicator to generate images as a unit called the Lynx Sar/GMTI. The company is now developing the high-resolution, digitally zoomed and large format Magnum Raptor View electro-optical system to supplement the Lynx. The idea is to use the ground moving target indicator function to cue the gimballed Magnum to provide a high-definition image, which can be geo-rectified. Little data is currently available from General Atomics as the Magnum is still being developed on company funds.

The Lynx I radar system, on the other hand, is operational on the US Air Force's Predator B, the US Army's I-Gnat ER and the Army's Sky Warrior Alpha, and has been flight tested on the Northrop Grumman Fire Scout. On the electro-optical theme, the General Atomics drones have so far been using Raytheon's sensor, the MTS-A on the Predator, the MTS-B and L-3 MX-20 ER/MP variants on the Predator B and the MTS-a with the L-3 MX-15 on the I-Gnat ER. As a matter of interest, and since the Predator series are male drones (medium-altitude long endurance), General Atomics uses satellite communications to relay data to ground stations with systems supplied by L-3, Enerdyne and Harris (Enerdyne and L-3 for the sitcom and modem, and Harris' APX 118 & 119 IFF for the transponder).

General Atomics is now offering the Lynx II, which provides the same performance as the Lynx I but for a much-reduced weight (36 kilos from 52).

In the unmanned aircraft context, Sagem is probably better known as the manufacturer of the Crecerelle (no longer manufactured but widely used during the ex-Yugoslavia conflict) and of the Sperwer drone system, which earned itself quite a reputation through its intensive and successful use by the Canadian Armed Forces in Afghanistan. Sagem, however, is also a long established thermal imaging system manufacturer. It is therefore not surprising to find a Sagem sensor under the chin of the Sperwer. The four-axis gimballed assembly is known as the Olosp and its core sensors are the 3-5 [micro]m Matis or 8-12 [mirco]m Iris. The Olosp is available in a variety of configurations (with a diameter of 350 mm for drones and 410 mm for helicopters) which will make weight fluctuate from 25 to 45 kilos and may incorporate an 8-12 [micro]m Iris module, together with a CCD colour or high-resolution black and white sensor, plus laser rangefinder and/or a laser tar get designator. A 350 Tactique version is available that houses a bi-focal Matis for observation mated to an uncooled 8-12 pm sensor for night 'piloting'.

Denel, maker of the tactical Seeker II and currently developer of the Bateleur male, produces the Goshawk 350 and 410 for, respectively, tactical and male drone applications but also has a comprehensive range of gimballed assemblies for larger manned aircraft, particularly surveillance helicopters. The 350 turret is intended for tactical drones and can house a variety of sensors. Interestingly, Denel offers both a standard and a hardened version of its aluminium turret, which, bare, weighs slightly less than 16 kilos, anti-icing heaters included. The four-axis gimbal offers a stabilisation accuracy of less than 25 [micro]radian.

Israel has not one, but three drone stabilised electro-optical sensor manufacturers; Elbit, Controp and Tamam (a division of IAI). Elbit, in addition to the sigint sensor mentioned at the beginning of this article, is also active in drone imagery intelligence mission payloads. Also renown for its extended range of air, land and marine thermal imagers, the company has recently introduced the Compass turret which incorporates a thermal imager, a colour television, a laser rangefinder-designator and a laser target illuminator.

IAI Tamam, for its part, offers a comprehensive range of electro-optical stabilised payloads in a range known as Pop (for Plug-in Optronic Payload). Nominally, the Pop is a dual-sensor system typically carrying a day television unit and a thermal camera. However, the unique feature of the Pop is its plug-in sensor module which can easily be replaced in the field in a matter of minutes. Indeed the central part of the 'ball' is removable and is very figuratively called the 'Slice'. It drops out of the ball, which merely acts as a calliper, to enable differently configured Slices to be slotted in to add a laser rangefinder, a laser pointer or automatic video tracking. The latest Pop 300, for instance, carries a 3-5 [micro]m, 640 x 480 matrix imager with three fields of view plus an electronic zoom that provides a field-of-view of 1.15[degrees] x 0.86[degrees]. The complete unit weighs 16 kilos and has a stabilisation accuracy of under 40 [micro]rad. Going downscale, Tamam also offers the MiniPop with a diameter of 204 mm, where most of the classical turrets hitherto examined have diameters of about 350 mm. A dual-axis system, the MiniPop retains the Slice concept but only weighs between seven and nine kilos, depending on which sensor option is installed. It offers a stabilisation accuracy of under [micro]rad and a slew rate of 120[degrees] per second (most of the larger units typically offer a slew rate of around 60[degrees] per second), but power consumption drops to about 50 watts (100 watt peak). Pushing the shrinking process even further, Tamam has developed the MicroPop to offer a one-kilo stabilised turret for mini-drones. It has a diameter of only ten centimetres over a height of 17 cm and comes with an uncooled 8-12 [micro]m, 320 x 240-pixel thermal imager, typically with a 7[degrees] field-of-view, although an option exists for a dual field-of-view. Here too, the Slice can be removed to emplace a day colour camera fitted with a continuous 4[degrees] to 46[degrees] field-of-view zoom.

While it would impossible to describe all available systems without turning this article into an encyclopaedia, one can also mention the L-3 BAI 1.5-kg Series 66 day or night system in the lightweight category and Optical Alchemy's more sophisticated retractable KG-600 series, which is currently undergoing testing with an MTC Technologies Arcturus T-16 as part of the US Marine Corps Tier II demonstration programme.