Low Cost Surface Movement
Radar
Kim O'Neil
Advanced Aviation
Technology Ltd.
Abstract
New radar technology can resolve many of the
problems associated with conventional airport surface movement radars. This
paper describes the DSMR-800 millimetric radar. Millimetric radars offer very
high resolution at ranges of 800m. These features can bring significant
technical and operational benefits as well as low cost. For example, by spacing
millimetric radar heads at appropriate intervals around the airport, it is
possible to provide 100% coverage and reduce shadowing or other problems
associated with conventional radars. The DSMR800 provides many other
performance benefits, including reliability and ease of maintenance.
1. Introduction
Surface Movement Radars (SMR) offer many useful
capabilities to improve the safety and efficiency of surface movement
operations by providing a real-time picture of aircraft and vehicles on the
runway surface and a range of operationally useful safety tools. In its
simplest role, SMRs help maintain the mental picture of the ground movement
controller - a useful and effective aid memoire that ensures the controller is
able to keep traffic moving safely and efficiently. Runway and taxiway
incursion warning functions also improve safety, preventing potential
collisions between aircraft and/or vehicles. Adding labels to the primary radar
targets improves this capability further and easing the controller's workload -
also enabling improvements in low visibility operations.
Traditional airport radars are expensive -
smaller airports may find they simply cannot afford or justify in terms of
operational benefits. Traditional radar solutions may also come with
limitations, such as poor coverage in important manoeuvring areas, shadowing
and intermittent performance problems.
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| SMR Radar head with older style
radome |
AAT's DSMR800 millimetric radars
overcomes many of these issues with powerful benefits at low cost. This paper
describes the DSMR800 and its
applications
2. Surface Movement Radar Requirements
The Top-level requirements to be met by a
surface movement radar are Safety and "Fitness for Purpose". The radar must be
able to meet the operational requirements of the customer as a surface movement
radar, taking account of airport geometry, traffic flow and must be certifiable
for its intended purpose. It must be able to meet all relevant explicit and
implicit regulatory requirements.
The radar system must be able to safely perform
its intended functions: To provide consistent, unambiguous, accurate and
reliable detection of aircraft and vehicles in the defined surveillance area,
ensuring that both the radar and derived radar data are adequately protected
against interference, failure or loss of integrity. The radar must fulfil the
technical needs of a Surface Movement Radar Service, the operational needs of
the airport and all applicable legal and regulatory requirements.
In particular, the radar system must be able to
meet the specific approval requirements of the National aviation authority, and
other relevant legislation such as Health and Safety.
3. Traditional Airport Radar Technology
Conventional X- band or Ku-band radars operate
from a single radar head, very often located on the ATC Tower. This can create
coverage problems depending on the location of the tower and adjacent terminal
building facilities. Future airport developments may steadily degrade coverage.
Consequently, many airports have significant holes in coverage, often in key
taxiway junctions as a result. This is just a natural consequence of geometry
and the difficulty of providing 100% coverage from a single location. Such
technologies are also power hungry and generate a huge radio output.
Many ATC towers have to be reinforced to cope
with the additional weight of the radar head and its turning gear. The physical
location itself can create maintenance problems and other unfortunate side
effects. The overall result can be both unsatisfactory and very expensive, with
continuing and escalating costs.
Technical or maintenance failures can lead to
the loss of the radar and this means complete loss of airport radar coverage.
For conventional "heavy duty" radars, this can last for some time and at great
operational cost to the airport, depending on the type of failure and the
repairs that may be required. Many technical failures are beyond the technical
capability of airport maintenance to fix, requiring manufacturer support (and
sometimes even the manufacturer can't help!). Downtimes of many days or even
months are not unusual. In particular, the airport may become dependent on the
manufacturer for expensive maintenance support and this support can be
problematic and frustrating. Even a failure in the turning gear can be
difficult to fix depending on the nature of the failure, availability of parts
and the response time of maintenance team.
To summarise: traditional airport radar
solutions are expensive to purchase, install and maintain, may have significant
holes in coverage and can suffer unacceptable outages.
4. New Millimetric Radar Technology
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Typical applications include:
- Gap filling
- Critical area surveillance
- Surface Movement Radar
- Runway/Taxiway incursion detection
- Area Penetration Monitoring
- Conflict Alert
- Foreign Object Detection
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The DMSR-800 77GHz Millimetre Wave FMCW radar is
a high performance radar system designed for use in industrial sensor
applications. Intended for continuous use in harsh environments, the system is
extremely rugged with built in self-test, condition monitoring and calibration.
A Radome provides protection against extreme weather conditions and potential
impact from small objects such as stones etc.
The unit provides a full 360 degrees scan at 1
Hz with target ranges up to 800m and range accuracy to +/- 0.25m. Different
scan rates are possible. The typical standard beam width is 1.6 degrees. Other
beam widths are also available.
The radar signal is digitised and processed
within the unit by a high speed DSP system. A standard 100mbit/s Ethernet link
or optical link is used transmit the radar data to provide a 'real time' visual
display of all the raw radar data.
Software maintenance updates can be performed by
laptop in the field.
The physical characteristics of each radar head
are:
- Transmit frequency 76 to 77 GHz
- Transmit Power 15dBm
- Beam width Antenna dependent, typically 1.6
degrees
- Max Range up to Approx 800m
- Range Accuracy ± 0.25m
- Scanner field of view 360 degrees
- Scan Speed 1 Hz. (other speeds optional)
- Interfaces 100MBit/s Ethernet
- Supply voltage +24V nominal (18-36V)
- Power consumption approx. 25W
- Supplied with Weather proof Radome
- Environmental IP66, IP68
- Temperature -20 to +70 degrees C
5. Radar Head Mounting
As can be seen from the inset picture, the
DSMR-800 radar heads are physically small, low power devices, weighing around
15kgs each and are mounted on 2m frangible masts. The masts are each fixed to a
small concrete plinth. Each radar head installation is designed to be entirely
frangible and the plinth represents no significant danger to any aircraft
inadvertently leaving the runway.
6. Surface Movement Radar System
When implemented as a surface movement radar
system, full coverage is achieved by installing several DSMR-800 radar heads,
located at appropriately surveyed points on the airport surface. The location
of each radar head is designed to give best coverage performance, whilst the
combined coverage aims to give complete coverage of the surveillance area of
interest. Each radar head provides a stream of primary radar targets, with or
without tracking (as required by the customer). The data streams from each head
are combined and duplicates removed to give a single stream of primary radar
data in a customer specified format.
Tower display technology can also be provided
(with and without tracking and/or labelling). The display technology can also
provide alerting functions, such as:
- Runway/Taxiway incursion detection
- Critical Area Penetration Monitoring
- Conflict Alert
Options exist to provide secondary surveillance
data for target labelling.
Radar display and secondary surveillance
solutions are the subject of separate articles.
7. SMR Capability
The DSMR-800 system typically provides
performance capabilities as follows:
- Complete and unambiguous radar surveillance
coverage
- Full target resolution and decluttering
- Better than 95% probability of detection
- Appropriate error flags indicating radar
status or failure state
- Generation of less than 1 false target per
revolution
- Resolution better that 0.5m
- Accuracy better than 2m
- Processed target centre (circle of
uncertainty) better than +/-5m
Integrity monitoring reports integrity failures
within 2 seconds (Integrity indicates whether target position can be safely
relied upon).
The SMR output is made available as a stream of
primary radar data in standard primary formats, suitable for direct input to
radar data display processing systems. This can be a display system proprietary
to AAT or any other customer preferred display system.
8. Other Airport Surveillance Applications
A wide range of specific airport surveillance
applications can also be met by the DSMR-800, these include:
8.1 Gap Filling
Where airports already have surface movement
radar systems installed, but still have significant holes in coverage (perhaps
due to shadowing caused by terminal buildings), it is possible to provide a
single radar head to provide coverage for specific areas. Such radar heads are
easily installed and can provide primary radar data in customer formats.
Providing such gap-filling radars may release the full capacity and safety
benefits of a currently installed airport SMR System.
8.2 Spot or Critical Area Surveillance
Some airports may not have the need for full
surface movement radar coverage, but may have specific problems such as poor
line of sight to critical taxiway junctions. Such junctions may have specific
procedures that currently limit runway capacity. In such cases, it is possible
to provide radar cover in just such critical areas, so that ATC are fully aware
of all movements that may affect aircraft safety. This is a very low cost
solution that may allow operational procedures to be re-written to
significantly improve airport capacity.
8.3 Incremental Surveillance: From Spot
Surveillance to Full SMR
Many small and medium sized airports cannot
justify the cost of a full SMR, but may require surveillance of critical areas
as already described. As traffic increases at the airport, they may wish to
increase the surveillance area - perhaps eventually to the whole airport
surface within an integrated SMR. This can be achieved with the DSMR-800, which
is fully upgradeable in defined steps towards a full SMR.
8.4 Foreign Object Detection
Another capability of millimetric radar is in
Foreign Object Debris (FOD) detection. A surprising amount of 'foreign objects'
can find their way onto taxiways or even onto the runway, often falling from
aircraft during taxiing or landing e.g. chocks, or other objects (tools etc)
that may also be dropped by workers or vehicles on the airport surface or
panels dropped by aircraft on landing. FOD on the taxiway surface can be blown
into following aircraft engine intakes by jetblast. The resulting damage is
usually catastrophic to the engine and very expensive for all concerned. Some
airports report surprising amounts of FOD, which is often recovered by regular
physical inspection of the movement areas. This can result in unnecessary
runway and taxiway inspections, reduced capacity and some small increased risk
to airport operations.
The resolution of 77GHz radars are sufficient to
detect objects with very small radar cross sections. Hence it is possible to
provide low cost FOD protection to reduce the risk of potentially very
expensive damage to aircraft.
9. Site surveying and Installation
Prior to installation, a full airport survey is
carried out and a clear definition of operational requirements is made
(coverage area, critical issues, capacity and flow rates, future developments
etc.). This helps in identifying optimal locations for each SMR radar head.
Each location is then studied for installation purposes (power, cabling etc)
and a risk assessment is carried out. The result is a technical proposal for
site installation and report of its likely impact on safety, coverage and
operational performance.
10. Maintenance and Reliability
Perhaps one of the key benefits of the DSMR-800
is in system reliability and ease of maintenance. Each radar head is highly
reliable, requiring minimal annual maintenance. If an individual radar head
fails, this causes only partial loss of surveillance on the airport surface.
However, each head is easily replaced (in less than an hour) restoring full
airport coverage. This means that the risk of loss of surveillance coverage is
very small indeed, whilst time to replace is very short (typically less than an
hour). Replaced units can be sent for test and overhaul at leisure. Their very
light-weight means that they can be sent rapidly to the manufacturer for
repair. Training can be provided to airport personnel to carry out maintenance
checks and relevant repair and replacement functions.
11. Certification
The DSMR-800 millimetric radar system complies
with published European Standards for the use of 77GHz radar and has been
certified and licensed for airport applications. Airport Safety Cases have been
constructed to support and demonstrate the safety of the SMR and these safety
cases have received regulatory approval. AAT offers this additional support
service, as a holistic solution to all customers to ensure rapid installation
and regulatory approval.
12. Summary
The AAT SMR solution makes it possible for all
airports to enjoy the genuine operational and safety benefits of airport
surface movement radar surveillance at low cost. SMR can significantly improve
safety, enabling airports to rewrite operational procedures to enhance capacity
and efficiency. Other applications include gap filling and critical area
monitoring and these applications can also significantly improve airport
operations at very low cost. It is also possible to provide effective FOD
protection. SMR coverage can be exceptional with minimal downtime and very low
maintenance costs. Technical support for early certification means that
transfer to service can be rapid, maximising this cost-effective
investment. |
