International airports adopt electronic-scanning Doppler radars to improve perimeter security and lower costs
Mark Radford of the
With the continued targeting of aviation by terrorist groups worldwide, attention is turning from the strict levels of security employed for passenger screening, to targeting backdoor threats from the relatively low-levels of perimeter security at many of the world’s tier one and tier two airports.
Traditionally, airports have employed large numbers of CCTV cameras and security personnel to monitor for perimeter intrusions. However, the typically flat, wide-open nature of airport topography allows ground surveillance radars (GSRs) to be installed as the primary sensor for the detection of breaches of the airport perimeter.
Sophisticated electronic-scanning (e-scan) GSRs are proving popular with international airports, such as London’s Heathrow, as they provide highly-reliable, maintenance-free surveillance of key airport zones in all weather and light conditions, as well as delivering improved intruder detection performance and considerable operational cost savings.
Challenges of deploying low-cost short-range radars for aviation security
Over the last five to 10 years, many tier one airports have experimented with the installation of relatively low-cost, short-range GSRs, usually as part of an integrated perimeter intrusion detection system (PIDS). Such radars have typically achieved maximum man-detection ranges of between 0.25 to 1 mi. (400 m to 1.6 km).
The relatively low capital outlay associated with these small, mechanically-scanned radars is initially very attractive to the airport operators. However, the short detection ranges offered by these products means that they must be located close to the perimeters and/or boundaries being monitored. This also means that they must be installed close to the operational taxiways and runways of the airport itself. This can give rise to high installation costs, due to the required networking and power cables that must be laid to control and power the multiple numbers of short-range radar units required to cover the distances involved. The digging-up and laying of cables can be disruptive to normal airport operations and, hence, often necessitates that installation work be carried out overnight.
Short-range perimeter surveillance radars also suffer from high false alarm rates. It can be very difficult for these mechanically-scanned sensors to distinguish genuine targets of interest from the large clutter returns caused by radar reflections from buildings, fences and other airport structures or objects. The airport apron will also have a large number of legitimate moving traffic of all shapes and sizes, from A380s to tugs and other ground support vehicles. The false detections are often caused by the relatively crude clutter-filtering techniques used in these non-Doppler radars. Airport operators have also experienced problems with high false alarm rates during periods of inclement weather (e.g., high-winds, rain, hail, snow, etc.)
Being intrinsically mechanical in their operation, rotating radars will offer poor reliability when compared with other fully solid-state security technology. If one considers the most unreliable components in the humble desktop PC, one immediately thinks of the rotating hard-disks and power supply cooling fans. The same is true with the rotating radars. To avoid possible breakdowns, there is therefore a need for regular routine maintenance of the drive belts and motors of the antenna turning gear. Of course, due to the location of the radars, this maintenance, somewhat inconveniently, has to be carried-out overnight, when the runways and taxiways are not being used. The overall inherent unreliability of mechanical systems leads to much higher through-life costs and longer periods of potential downtime of the security system.
Benefits of long-range electronic-scanning Doppler radars
Recent developments in electronic-scanning (e-scan) radars has seen a move away from the expensive and power-hungry AESA (active electronically scanned array) military radar technology to the newer and much lower-cost PESA (passive electronically scanned array) radar technology. The lower cost entry point allows PESA security radars to be employed for both their traditional military force protection roles, as well as some more cost-sensitive roles in homeland security, such as securing critical infrastructure, such as airports and seaports.
Using PESA technology, man detection ranges out to 3, 5 or 7.5 mi. (5, 8 or 12 km) and ultra-wide elevation beams (up to 20 degrees) can be achieved. This allows the radars to stand-off from the area to be surveilled and instead be mounted on top of existing airport buildings, giving clear line-of-sight to the airport perimeter, while still maintaining the full integrity of the radar coverage zone. Being able to mount the sensors on the existing airport terminal gates and piers allows for ease of connection to readily available sources of power and network connectivity.
Fully e-scan radars are entirely solid-state with no moving parts and, hence, have no requirement for any routine maintenance of the system. Such radars are said to be “zero maintenance” with much lower associated through-life costs and a long in-service life of up to 10 years or more.
PESA radars usually include a fully-integrated Doppler processing engine, unlike their counterparts which often require external radar processing servers or PCs that then need to be hosted in a remote server room at the airport. Another benefit of e-scanning radars is that during scanning, the radar’s microwave beam is entirely stationary, allowing such systems to detect very small and slow moving targets in extremely cluttered environments. This improves their detection capabilities and reduces the false alarm rate.
Contrast this with mechanically rotating radars, where the reflected signals received by the radar are always blurred by the continuous rotational movement of the antenna. The benefits of PESA e-scan radars are clear: lower installation costs, lower through-life costs and lower false-alarm rates.
Application example: London Heathrow Airport
Heathrow Airport is the world’s busiest international airport. Over 67 million passengers travel through the airport annually on services offered by 90 airlines, travelling to more than 180 destinations in more than 90 countries. Plextek’s Blighter B400 series e-scan PESA radars, with FMCW (frequency modulated continuous wave) technology and Doppler processing, form part of an integrated perimeter security system, supplied to BAA Ltd, the airport operator that owns Heathrow.
The complete airport perimeter surveillance solution includes long-range day and night cameras and a network of high definition cameras, capable of identifying and tracking intruders detected by the radar. BAA needed a highly reliable, maintenance-free system that could provide intensive 24-hour surveillance of the airport in all weather and light conditions. The Blighter Doppler system proved technically superior to previous systems and met BAA’s requirements in full. Since deployment, the system has led to considerable operational savings, reduced security staff costs, with a marked improvement in detection.