Rise of the all-weather UAV.
In February 2004, Australia announced that it will spend one billion of its dollars (US$ 770 million) to procure a squadron of drones (as UAVs were originally known in the United States) to handle the maritime patrol task and to fulfil land surveillance and intelligence gathering roles. The requirement is for a high-altitude, long-endurance aircraft able to enter service between 2009 and 2011, and although the contractor and sensor payload have yet to be chosen, it is likely that the winning design will be fitted with a Synthetic Aperture Radar (Sar).
One likely candidate for the order must be the Northrop Grumman RQ-4 Global Hawk. In his announcement of the proposed procurement--part of Australia's Defence Capability Plan 2004-2014--Australian Defence Minister Robert Hill highlighted the success that the Global Hawk has had during American operations in Iraq and Afghanistan.
The Global Hawk has already demonstrated its usefulness to the Australian armed forces. In the summer of 2001 a Global Hawk flew eleven demonstration missions over Australia and the surrounding seas, allowing that nation to evaluate its ability to meet a Royal Australian Air Force strategic surveillance requirement.
The aircraft's definitive sensor suite is currently a Raytheon (originally Hughes) package known as the Integrated Sensor Suite (ISS). This teams electro-optical and infrared sensors with a Sar whose gimballed antenna scans from either side of the vehicle. A plan to replace the current Sar by a new variant of the Raytheon Asars-2 carried by the Lockheed Martin U-2S reconnaissance aircraft has been reported. Around 2009 the Global Hawk is due to receive an active electronically scanned array (Aesa) Sar created under the Multi-Platform Radar Technology Insertion Program (MP-Rtip).
As these words were being written in early February 2004, Britain was about to select a consortium to develop and supply UAVs to meet the Watchkeeper requirement. Currently the main British drone project, the Watchkeeper is intended to support land forces. Due to reach an initial operating capability in early 2006, Watchkeeper is expected to have a service life of 30 years.
Following the successful use of unmanned aircraft in Afghanistan, the United Kingdom decided to accelerate the Watchkeeper programme, downselecting two consortia to proceed to the next phase of the project, and setting up a new joint service trials unit to begin testing prototypes of the system.
BAE Systems, Lockheed Martin, Northrop Grumman and Thales all took part in the first stage of the Assessment Phase. Northrop Grumman Integrated Systems and Thales (UK) were selected to continue through to the System Integration Assurance Phase, which was intended to prove the integrated capability of the proposed system and to provide the customer with a high degree of confidence that the chosen design could be delivered on time and within budget.
Thales has teamed with Elbit Systems (air vehicles clement), LogicaCMG (digital battlespace integration), Cubic (datalinks), Vega (training) and Marshall SV (vehicles and shelters). Tamam, Thales Optronics/Elop and L3 Wescam competed for the task of providing the electro-optic sensor package. Other team members are QinetiQ, Supacat, Praxis and a number of Thales UK companies.
Two designs are being offered by the Thales-led consortium, these are based on Elbit's Hermes 180 and 450:
* the WK180 air vehicle offers field reconfigurable payload and launch options, allowing a choice of ramp/parachute & airbags, ramp/short strip or strip/strip launch and recovery; it is designed to be air-transportable as a single C-130 load, and able to be operational within an hour of arriving at its operational area: the normal payload is likely to combine an electro-optical suite with a laser marker.
* the larger WK450 air vehicle has almost twice the endurance of the WK180, but carries multiple payloads including a latest state-of-the-art Sar/GMTI radar: capable of fully autonomous ramp or runway launch, it shares many common subsystems and avionics with the WK180, and will be C130 deployable.
Northrop Grumman Integrated Systems evaluated the ability of several unmanned systems to meet the Watchkeeper requirements, including its vertical takeoff and landing RQ-8A Fire Scout. At the 2003 Paris Air Show, the company announced that it had completed the integration and end-to-end air vehicle/payload testing of a General Atomics AN/APY-8 tactical synthetic aperture radar on the Fire Scout. (The AN/APY-8 was originally developed for use on the General Atomics Predator, and is described later in this article.)
The Fire Scout had been fitted with the AN/APY-8 gimballed antenna assembly and radar electronics assembly, an independent Global Positioning System and a Northrop Grumman-designed and -qualified Sar/MTI interface unit intended to allow control of the radar via the UAV's existing tactical command data link.
The radar would enhance the Fire Scout's ability to perform missions day and night in all weather conditions, while increasing the system's search volume and detection range, explained Tom Soard, Northrop Grumman's Fire Scout programme manager.
The tests carried out to meet the Watchkeeper requirement were intended to demonstrate that the performance of the radar was not degraded by its installation on a rotary-wing vehicle, to display and record Sar imagery at the Fire Scout ground control station, demonstrate ground moving target indicator functionality and simultaneously operate the baseline Fire Scout electro-optical suite Sar/MTI payloads during missions.
Should the Fire Scout be chosen, the possibility of a limited shipboard deployment of the system would increase, but despite this, the Watchkeeper would still be intended to support the land units rather than the Maritime Component Commander.
Tight UK defence funding rules out the development of a purely maritime UAV. While there is no plan to base Watchkeepers aboard Royal Navy ships, it is planned that LPD/LPH vessels will have facilities to access or control the vehicle's sensor payload. This capability, however, has not yet been funded.
Another Lynx/Fire Scout application is the US Army's Future Combat System (FCS) programme. Boeing has awarded Northrop Grumman an eight-year, $ 115 million contract for the system development and demonstration phase of the FCS UAV project. During this phase, Northrop Grumman's Integrated Systems sector will produce seven RQ-8B Fire Scout air vehicles, perform system tests and evaluations and help develop long-lead future requirements.
The RQ-8B air vehicles will feature a new, four-blade rotor system (versus the RQ-8A's three-blade design), improved airfoil blades and several performance enhancements that will give them more than eight hours endurance with a 59 kg payload.
Company-sponsored engineering tests suggest that the new rotor will triple the Fire Scout's maximum payload capacity to 272 kg, double its on-station time at 110 nm with a 90 kg payload and increase its ability to carry multiple payloads.
In July and October of 2003, the three-bladed RQ-8A air vehicle flew 13 flights carrying the General Atomics Lynx synthetic aperture radar with Ground Moving Target Indicator (GMTI) the baseline electro-optical/infrared/laser designator rangefinder and a communications relay payload--a combined payload weight of approximately 195 kg.
The original Sar carried by the General Atomics Predator was the Northrop Grumman AN/ZPQ-1 Tactical Endurance Synthetic Aperture Radar (Tesar). Designed to provide critical intelligence of enemy ground forces and bomb damage assessment, this 75 kg J-band unit operates in Sar strip map, Sar spot map and MTI modes, providing high-resolution imagery in poor weather conditions, up to four mm/hr of rain with low cloud cover and through smoke, haze and fog.
Northrop Grumman has delivered 54 Tesar radar systems and 10 ground radar displays. Additional capability for moving target indication has been developed and demonstrated for potential retrofit into the 80 systems under contract. An upgrade to a Power PC-based processor has been developed to allow users to incorporate improved capabilities.
General Atomics now offers its Lynx Sar/GMTI radar fur use on the Predator and other UAVs. The Lynx uses Sar/GMTI technology developed by the US Department of Energy's Sandia National Laboratories. General Atomics funded Sandia to develop and deliver two prototype units with the associated software code. These radars involved extensive development instrumentation and weighed 220 kg.
In developing the design into production hardware, General Atomics reduced the weight to 52 kg. To allow the Lynx to be carried by the General Atomics Prowler II, the company further trimmed the radar's weight to about 45 kg. This modified design retains the resolution of the basic version, but has a slightly reduced radar range. The Lynx can provide its output in a variety of formats and is thus compatible with commonly used transmission links. If required, its imagery can be transmitted directly into the cockpit of tactical aircraft.
The Lynx already offers a coherent change detection mode that operates in near-real time, allowing it to detect very small changes in the scene from one pass to another over the same area. Further upgrades could include an inverse Sar mode for imaging of seaborne targets, interferometric Sar for three-dimensional imaging, enhanced GMTI and the ability to cue other sensors. Additional cognitive enhancements are planned to make the radar image more easily understandable, including an eventual incorporation of automatic target recognition
The Lynx has undergone tests involving General Atomics' Athena RF tag. Designed to work with the Lynx and other radars to provide blue-force tracking and combat ID, the Athena tag has already been successfully trialled with the Jstars. The company is now exploring the tag's potential interoperability with the British Astor. Tags could also be attached to a target by ground units such as Special Forces.
In December 2002, the US Army awarded AAI an $ 86 million contract for full-rate production of an initial nine RQ-7A Shadow 200 Tactical UAV (TUAV) systems, six attrition air vehicles and associated equipment. The first UAV manufactured under this contract was delivered in the autumn of 2003.
The US Army plans to field at least 41 brigade-level RQ-7A Shadow 200 systems, each of which include four air vehicles, two ground control stations, two ground data terminals, a portable GCS, a launcher, a Tactical Automatic Landing Systems arresting gear.
The RQ-7A will carry a Ku-band radar currently under development by Northrop Grumman as a derivative of the AN/ZPQ-1 used on the Predator.
The Shadow 400 is a slightly larger version designed for naval applications. The (265kg Gtow) Shadow 600 has an endurance of 12 to 14 hours carrying a 41 kg payload. It is powered by the UAV Engines AR801 52 hp powerplant.
In 2003, the Hunter successfully demonstrated enhanced reconnaissance capabilities during an 8 through 14 May series of operational missions flown by the US Army at Fort Huachuca, Arizona. The tests were co-sponsored by the Army's Unmanned Aerial Vehicle and Robotics and Unmanned Sensors programme offices. The demonstration culminated in a mission involving two Hunters, one carrying the Northrop Sar and moving target indicator and the other equipped with the Hunter's standard electro-optical/infrared payload. Using the radar's ability to toggle between synthetic aperture imaging and moving target detection modes, plus sensor cross-cueing techniques, operators were able to survey the entire target area and then positively identify them with the second Hunter's EO/IR sensor.
The EL/M-2055 Sar developed by IAI's Elta subsidiary has been flight-tested on a number of UAVs, including the IAI/Eads Eagle 1 (basically the Israeli Heron) offered to the French Air Force, the IAI Hermes 450, and the Malat Searcher II. A derivative of Elta's EL/ M-2060P pod-mounted Sar/MTI radar used by the Israeli Air Force on F-16 fighters, the EL/M-2055 is available in two versions--a 36 kg system intended for use on tactical drones, and a 66 kg version for medium-endurance systems. Power consumption of these variants are 700 and 1100 Watts respectively.
The Hermes 450 was selected by the US Joint Unmanned Aerial Vehicles Joint Test & Evaluation Program Office as a testbed for the investigation and development of future UAV tactics, techniques and procedures. Operating from Naval Air Station Fallon, Nevada in late 2003, the Hermes 450 conducted 26 consecutive flights without a missed sortie, and eight fully mission-capable flights in the first seven days of field testing.
When the Royal Danish Air Force selected the Sagem Sperwer, it announced that the system would carry a camera plus a high-resolution Sagem infrared camera, but that the integration of a Sar was planned to allow all-weather operation.
Some two years ago, Sagem announced two new drones to form a Sperwer family of drones suffixed HV and LE (respectively for high velocity and long endurance), both able to carry a Sar, a high performance electro-optical suite (such as a line scanner or gimballed pod) or a laser designator. Key to the family expansion idea was the use of a common launcher and ground station for all Sperwers. However, following Sagem's tight links with Dassault in the field of larger and attack drones, the forward-swept wing and canard controlled HV project was cancelled, leaving the family growth role to the Sperwer LE, which is able to cruise for up to twelve hours at an altitude of 20,000 ft.
Rheinmetall Defence Electronics also uses synthetic aperture radar technology in the all-weather seeker head of its Taifun. Being half a drone and half a missile the Taifun is an unusual species. Once the vehicle has reached the designated engagement area, the Sar enters a high-resolution search mode. Potential targets are compared and correlated with a predefined target database. Any targets found are selected automatically by the mission program. An HF datalink is used to send information concerning air vehicle status and target acquisition to the ground control station, but a UHF datalink is used to transfer radar images of current potential targets to the ground allowing targets to be selected by an operator. Once an attack decision is made, the Taifun is committed to a steep dive. Although this is flown at high speed, the air vehicle can be manoeuvred to hit the optimal location on the target. The warhead is triggered at an optimal distance to allow penetration of heavily armoured targets. It also releases fragments in a radial pattern.
Another potential Sar carrier is the Nibbio from Galileo. Derived from the Mirach 100/5 target drone, this newcomer should take to the air later this year or in 2005 (see Drone Update in this issue).
Resolute to Resolve
Synthetic aperture radars must rely on high-capacity datalinks to transmit their high-resolution imagery to the ground. Distributing this imagery, to the front-line units that need it will not be easy, given the narrow bandwidth of tactical communications channels. Image compression algorithms reduce the amount of data that needs to be transmitted in order to send a picture, but these are often 'lossy', and reduce the quality of the final image.
Perhaps the best-known 'lossy' algorithm is the Joint Photographic Experts Group (Jpeg) standard widely used to send pictures over the Internet. As many computer users realise, the greater the degree of compression, the poorer the quality of the final image, while resaving (and thus recompressing) a Jpeg image can create even greater degradation.
Newer algorithms may offer a solution. For example, in a project sponsored by the US Defense Advanced Research Projects Agency, a team of SAIC researchers led by Dr John Irvine have tested the ability of military imagery analysts to extract intelligence from Sar radar imagery compressed at ratios of 50-to-1 and 100-to-1 by several image compression techniques, including intelligent bandwidth compression (IBC), wavelet/trellis-coded quantization (which SAIC and the University of Arizona developed), and Jpeg. Their experiments suggest that both the intelligent bandwidth compression and wavelet/trellis-coded quantization techniques could provide images of value to a tactical user.
Whether a UAV is considered an expendable or attritable asset depends on a number of factors. The greater the cost of the vehicle, the less likely the operator will be to risk its loss. During combat operations, cost may give way to operational urgency--at least one combat loss of a Predator was the result of the system being operated in a manner which seemed likely to result in its destruction in order to support the recovery on a downed airman.
While rating UAVs as attritable or non-attritable purely in terms of cost is overly simplistic, the fact remains that Sat-equipped drones are likely to be more expensive than their electro-optical payload counterparts. The door to airborne countermeasures is open.
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|Title Annotation:||Drones: SAR|
|Date:||Apr 1, 2004|
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