Electronic Warfare Capabilities of Mini UAVs Abstract David Ledger 1 Mini UAVs are at the leading edge of robotic systems being introduced into the Electronic Warfare environment. The Aerosonde Robotic Aircraft is one example of these mini UAV systems that provide an increasing range of unique EW capabilities, which will present challenges to traditional EW doctrine. The Aerosonde is a low cost, high endurance UAV that has a number of unique characteristics. Its combination of small size and endurance is unmatched by any other UAV on the market. It is also one of the few UAVs to have an established commercial market, providing weather reconnaissance missions in a wide range of global locations. The Aerosonde system consists of a fleet of aircraft, a ground command system and a launch and recovery system. Normal operations are provided by an expert operations team, who are backed up by production, maintenance and development groups. Last year Saab Systems made a major investment in the Aerosonde and began moving this platform into the military market. Since then a comprehensive EW payload development and trials program has been established with the Australian Defence Science and Technology Organisation. These trials have been pushing the boundaries of airborne EW and have demonstrated the viability of mini UAVs as EW platforms. This paper presents details of the capabilities and operational characteristics of the Aerosonde UAV system, explores the advantages of EW UAV systems, examines available and planned EW payloads, highlights proposed applications of EW UAVs in Network Centric Warfare and provides background information on the EW UAV trials program in Australia. INTRODUCTION Historically the high power and large size of airborne Electronic Warfare equipment has constrained its deployment to manned aircraft or large UAVs. More recently the miniaturisation of RF components and small form factor processor boards has led to the development of EW systems capable of installation in mini-uavs. These types of UAVs are generally classified as having a wingspan of less than 4 metres and a payload capacity less than 15 Kg. Australia has begun a multi-year program to explore the boundaries of the new RF and processor technology through a series of EW trials based on the Aerosonde mini- UAV. The initial trials conducted to-date have confirmed the viability of the Aerosonde as a platform capable of performing a wide range of EW functions. The ability to deploy these payloads for flight durations in excess of 24 hours at operational ranges over 1500km has raised considerable interest at the highest levels of the Australian Defence Force. Both the Defence Science and Technology Organisation and Saab have invested considerable research and development in Network Centric Warfare and the EW equipped Aerosonde has already been integrated into both the EXC3ITE system and the Swedish Wide Area Situation Picture (WASP) and NETC4I systems. AEROSONDE UAV The Aerosonde UAV was originally designed to provide economical weather reconnaissance in remote and dangerous areas. As such, the aircraft have limited redundancy features and are considered expendable. Aerosondes began participating in meteorological field trials in1995, and have since performed over 3500 hours for meteorological applications in Australia, North America, Japan and Taiwan. The following table identifies the current specifications of the Mark 3 Aerosonde. Specification Weight, wing span Engine Full Fuel Load Navigation Max. Communication Range via UHF On board power generation MTBF Operation Staff for Launch and Recovery Ground & air communications 13-15 kg, 2.9 m 24 cc, Fuel Injected H type. 5 Kgs GPS, automatic front tracking 180 Km depending on height and terrain Maxon generator providing 18 v DC at 1 Amp, 40 W continuous, 60 W peak, 30W for Payload 250 hours 2-3: Controller, Engineer, Pilot/Maintenance UHF or SatComms to/from Aerosonde, VHF to field staff and other aircraft, internet to command centre and customers. Performance Speed, Climb 18 32 ms -1, Climb >2.5 ms -1 Endurance, Range Weather mode 20 to 30 h, 2000 to Altitude Range Payload 3000Km. (No Wind Range) 100 m >7000 m (intermediate weight), Max 5 kg ~ 10 hour endurance. Max 2 kg ~ 30 hour endurance. The vehicle is autonomous and is easily programmed to perform desired missions for the end-user. The Aerosonde 1 Aerosonde Program Manager, Saab Systems
operates in a completely robotic mode with command being exercised by local operators or from a centre that may be many thousands of kilometres away. The aircraft have been tested, and conducted operations, in a variety of conditions from the tropics to the Arctic and in all weather conditions. The aircraft uses a modified ENYA model aircraft engine to be a small, fuel-efficient air-cooled aircraft engine. Operating constraints include the ability to fly at altitudes between the surface and 20,000 feet; the ability to operate between 40 and 60 deg C (ambient) and an endurance of greater than 30 hours. The power plant is capable of generating 60W, with 30W available for payload power. Launch System Air Vehicle Figure 1. Aerosonde UAV The Aerosonde (Mk3) is configured as a "pusher" with the engine at the back, as shown in Figure 1. Airframe The airframe consists of a hollow composite structure with a carbon spar designed for loadings ranging between 1 to 5 kg. Informal design verification includes: landing shock tests, wing loading tests, boom stiffness tests and flight testing. Avionics The avionics hardware consists of: a. main flight computer and a payload computer, used for meteorological measurements and other specialist sensors (2xTT8 processors), b. Trimble GPS for way-point navigation and wind measurements, c. piezoelectric rate gyros for stabilisation and navigation, d. air data sensors for airspeed and altitude measurement, engine sensors, and e. power conditioning electronics. Communications Communications between the aircraft and the ground station is achieved via UHF radio (ranges up to 150 km) and via Iridium Low Earth Orbit (LEO) satellite (over-thehorizon global coverage). The Launch system consists of a cradle assembly, which mounts on the roofrack of any standard vehicle. The Aerosonde is placed in the cradle and secured with a quick release strap. After functional checks of avionics and control surfaces the engine is started using a hand held friction motor. Once current wind direction has been established the vehicle accelerates up to 80km/h, at which point the aircraft is released and begins climbing under manual pilot control. The pilot manoeuvres the aircraft up to a predetermined altitude and, with a flick of a switch on the Pilot Console, hands over control to the onboard avionics computer. At this point the aircraft begins executing the stored mission plan. Full telemetry contact is maintained throughout this procedure. Ground Control Station The Ground Control Station (GCS) is the primary launch, recovery and operational site for an Aerosonde mission. The GCS is a compact, mobile system, which has been successfully deployed to remote localities throughout the world. It has the following elements: a. Mission Planning and Control System (MPCS) b. Launch System c. Support Elements The core of the MPCS contains a MUX computer connected to a 9600 baud UHF radio modem. The MUX computer supports a TDMA interface providing a 2400 bps bi-directional telemetry channel for each of up to three aircraft in simultaneous operation on the same channel. The radio modem operates in the 402-417 MHz band. Connected to the MPCS are mission planning and telemetry computers. An MPCS stage boxes can support simultaneous command and control of up to three aircraft. Depending on the mission and level of payload integration the MPCS can also control payload function. Alternatively a separate communications channel can be provided to the aircraft to support a complex payload datalink. In standard configuration an MPCS can be successfully deployed in the back of a van. High bandwidth payload data, such as video, requires a separate datalink if this information is to be received at the GCS.. Engine
ADVANTAGES OF EW UAV SYSTEMS The range advantage of sensors located at altitude has been known since the early days of EW. The large size and high power requirements of previous generations of ES equipment limited deployment to larger manned aircraft. Unfortunately the low bandwidth associated with mobile airborne platforms has also meant that the majority of these airborne sensors operated independently with correlation achieved through either voice or very limited data links. The more recent introduction of Link-16 has introduced the possibility of multiple airborne EW sensors feeding a C2 system capable of auto-correlation and data fusion. The high cost of Link-16 and other military data links, particularly for airborne platforms, has limited the introduction of these systems to the world's larger air forces. The development of miniature EW payloads capable of deployment in UAVs has opened a whole spectrum of capability for resource limited defence forces. The demands of UAV telemetry and control have led to the development of data links with increasing bandwidth, as well as the introduction of Low Earth Orbit satellite links for global coverage. A number of UAV manufacturers have also developed low-cost TDMA data links, which can support multiple UAVs. The Aerosonde system, for example, uses a 9600 bps radio link with TDMA to provide 2400 bps channels to up to three aircraft from a single ground station. The robotic nature of UAVs provides a precision EW platform as they can provide continuous data on course, speed, attitude and GPS position. This data is relayed to the ground along with the EW pulse data and bearing information, which allows C2 software to perform a number of data smoothing functions and correlation or data fusion with other track sources multiple EW UAVs. It is cheaper and technically easier to design and build UAVs with stealth characteristics. The ability to deploy low-cost stealthy EW platforms into the combat environment opens up a range of new operational paradigms. Firstly flights of 3 or more ES equipped stealthy UAVs can provide a system to instantaneously vector a threat emitter. This can provide targeting information for indirect fire weapons. Alternatively loitering EA equipped UAVs can be tasked to barrage or spot jam individual threat emitters. The high mobility and endurance of these systems allows them to move with the flow of the battlefield and the stealthy characteristics dramatically improve survivability. Another interesting advantage is the ability to place EA emitters in close proximity to the threat emitter, which allows quite low power jamming of both main beam and side-lobes. The mini-uav, in particular, is well suited to this type of EW environment and a major component of the current DSTO trials program is the development of EW payloads which allow exploration of the tactical advantages of these new capabilities. EW UAV PAYLOADS A number of EW payloads have already been developed for the Aerosonde UAV. These include: ES Superhet Receiver ES IFM Receiver EA Noise Jammer RF Repeater (Jammer Test Target) These payloads have been flown in a number of trials against land based and shipboard radars. The most recent trials involved EW operations against one of the ANZAC class ships off the East Coast of Australia. ES Superhet Receiver This unit weighs in at 2.7kg and operates in the frequency range 2-18 GHz. A separate datalink is used to transmit pulse descriptor words out to a range of 12 km. The unit is installed in the Aerosonde with switching between two antennas, each with a beamwidth of 180 degrees, as shown in Figure 2. Figure 2. Aerosonde Equipped With ES Superhet ES IFM Receiver The IFM receiver also operates in the 2-18 GHz band with an RF resolution of approximately 4 MHz. The unit weighs approximately 3 kg and requires 30W of payload power. This payload uses the same datalink as the ES Superhet. EA Noise Jammer The noise jammer operates in two bands, high-band 8-12 GHz through tunable horns mounted in shields either side of the aircraft, and low-band 850-950 MHz through Yagi antennas mounted under the wings. The installation configuration is shown in Figure 3.
Hamilton (Sep 2002) Aerosonde live integration in Network Centric Warfare Demonstration (Wide Area Situation Picture interface) Planned Trials Figure 3. Aerosonde Equipped With EA Jammer RF Repeater (Jammer Test Target) The RF Repeater was developed to provide a target of selectable Radar Cross-Section to validate the masking performance of the jammer against a number of radars. The repeater can generate an apparent RCS of up to 10m2 and weighs 2 kg Future EW Payloads Currently lighter weight and improved versions of all of the above payloads are under development and will be trialed early next year. Additional design effort has been focused on the development of a modular payload system, which will provide scalable and interchangeable cards to build specific EW applications. A typical module would include processor, power conditioning, multiple RF and datalink cards mounted on a common bus. An R&D program is also underway to provide a more powerful Payload Computer using COTS PC-104 processor boards, Linux operating system and standard interfaces (RS-232, USB, IDE). This will allow significant onboard processing and storage as well as providing a plug & play environment for the payload modules. TRIALS PROGRAM The following mini-uav EW flight trials have been conducted by DSTO, Aerosonde and Saab Systems over the last 18 months: Hamilton Trial (April 2000) EO payload & Communications tested. Demonstrated autonomous flight modes and transfer of C2 and data links. Hamilton Trial (Dec 2001) ES, EA, & EO payloads & comms tested Single UAV, land-based, C2 infrastructure Jervis Bay (June 2002) Two UAV s, ES and EA payloads Land launch with C2 hand-over to warship SA information piped to ship & EXC3ITE Darwin (April 2003) IFM, Superhet ES payloads EA and RF Repeater payloads EO payloads with tracker control ES cross cueing for DF and geolocation EA against a significant asset DF and geolocation cueing EO SA information through EXC3ITE to deployed user Four UAVs, C2 infrastructure EW MINI UAVS IN NETWORK CENTRIC WARFARE Both DSTO and Saab have significant R&D programs to develop Network Centric Warfare capabilities. The EW Aerosonde has been successfully integrated into both the DSTO EXC3ITE system and the Saab WASP system. DSTO EXC3ITE Interface The Experimental C3I Technology Environment (EXC3ITE) is an environment within which concepts and technology for future C3I capabilities can be explored and developed. EXC3ITE is the integrator for the C3I R&D undertaken in DSTO s Takari R&D program. Takari s EXC3ITE environment will be key to the establishment of modelling and simulation (M&S) architectures, practices and capabilities that are integrated with real C3I systems to support a range of military experimentation. During recent trials with DSTO the Aerosonde carried Electronic Support payloads, which transmitted real-time emitter bearings and pulse analysis data to the ground station. From there a mobile Satcom link transferred the data to the EXC3ITE system. This in turn provided a direct interface to the Australian Defence Headquarters. The overall result was Australian Defence Force operational staff in Sydney, Canberra and Darwin were able to view a real-time EW picture off the east coast of Australia. NCW WASP Interface Saab Systems has recently completed an interface between the Aerosonde mission management system and the Saab Network Centric Warfare Wide Area Situation Picture system to inject real-time Aerosonde tracks and altitude data. The interface was demonstrated at a Network Enabled Operations Seminar in Canberra, Australia. The WASP provides a data fusion environment for new and legacy sensors and C2 systems and has been trialed extensively in Sweden.
CONCLUSIONS The current DSTO EW trials program has demonstrated the viability and potential of mini-uavs to effectively carry these payloads. This has opened the way to further miniaturisation of existing payloads and the development of operational doctrine and data fusion techniques to maximise the effectiveness of these low-cost EW platforms. ACKNOWLEDGEMENTS The author would like to thank Dr Greg Holland of Aerosonde Ltd, for cooperation in providing background data and photographs of EW payloads, Dr Kim Brown and Dr Tony Lindsay of DSTO Electronic Warfare Division for information on payloads and the trials program