This document discusses shore-based high frequency surface wave radars (HFSWR) developed by Raytheon to provide continuous surveillance of coastal waters and exclusive economic zones. HFSWRs can detect vessels at greater ranges than traditional radars by using ionospheric refraction to follow the curvature of the Earth. The document describes how HFSWRs work, their detection capabilities, and how they allowed anomalous vessel behavior to be identified in past incidents. HFSWRs provide cost-effective persistent maritime surveillance.

1. I'-l rotectinq a nation's sovereignty and
p.x".,,r.iy managing the natural re-
Lorr.., around its coasts place new
demands on the organizations tasked with
surveillance and enforcement. As a general
principle, the level of surveillance required
at any given time depends on the perceived
threat. The ideal surveillance system must
be capable of normal, day-to-day operation
for the lowest possible cost, yet have the
integrity to allow enforcement agencies to
respond decisively and economically when
required.
Until recently, such a surveillance system did
not exist. Now, however, shore-based high
frequency surface wave radars (HFSWR) de-
veloped by Raytheon can provide persistent
(contin uous), cost-effective, over-the-hori-
zon surveillance up to and beyond the 200
nautical mile limit of the exclusive economic
zone (EEZ*). Surface wave radar developed
by Raytheon Canada Limited, a leader in
surveillance and navigation systems, is the
only land-based radar with this capability.
*EEZ
- An area extending 200 nm beyond a
nation's shores, for which it has special rights
regarding the use of marine resources.
I-
The need for persistent surveillance is il-
lustrated by an incident that occurred on
July 31, 20'1 1 when a 1,000 ton, general
cargo vessel, the Panama-flagged MV
Pavit, grounded on Juhu beach in Mumbai,
lndia (Figure I). lt was later determined
that the vessel was abandoned on June
29 near Oman. The vessel drifted into the
Arabian Sea and entered India's EEZ. The
MV Pavit passed undetected through one
of the world's busiest shipping lanes dur-
ing a heightened level of alert following
the Mumbai terrorist attacks. ln doing so,
it passed through three tiers of security
-the Navy, the Coast Guard and the Coastal
Wing of the Mumbai Police
- before even-
tually grounding. Had an HFSWR been
installed, this vessel could have been ob-
served as it entered the lndian EEZ and
appropriate action could have been taken.
Surface wave radars operate in the high fre-
quency (HF) portion of the radio frequency
(RF) spectrum. As illustrated in Figure 2 (fol-
lowing page), the lower the frequency of
operation the greater the detection range.
Unlike traditional microwave radars whose
detection range is limited to the line-of-sight
horizon, HFSWR signals follow the curvature
of the Earth due to ionospheric refraction at
the frequencies in which they operate. This
enables the detection of surface vessels at
significantly greater ranges.
HFSWRs operate in a pulse-Doppler mode,
emitting a coherent pulse train where the
phase of the signal is precisely controlled
from pulse to pulse. The radar's area of
coverage is symmetrical around the radar's
boresight, where the boresight is perpen-
dicular to the axis of the array. Returns
continued on page 26
Figure 1. The MV Pavit
grounded on luhu Beach,
Mumbai on July 31,2011. The
vessel went undetected since
being abandoned on June 29,
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2012 TSSUE 2 25
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continued from page 25
Microwave
Radar
Coastal Microwave Radar
0nly operates in line-of-sight mode.
Generally limited to first 20 or 30 nm.
15 MHz
High Frequency Surface Wave
The lower the frequency the 1
range. Typical minimum range is
The maximum detection range of HFSWR
depends on many factors. These include
the transmrt power, radar frequency, radar
cross section of the target, target range,
background noise, and interference level as
well as sea-state. Of these, only the transmit
power and transmit frequency are under
the control of the radar. Both the noise and
interference levels are dependent on the
geographic location of the radar site, time-
of-day and season, and also on the level of
sunspot activity.
from beyond +/- 60 degrees in azimuth are
typically not displayed due to a rapid falloff
in system performance. The echoes from
objects within the area illuminated by the
radar are received by a linear array of anten-
nas (Figure 3) and are digitally processed to
enhance detection of the wanted echoes.
The returning echoes are sorted according
to range, velocity (Doppler) and bearing.
The echoes are then compared against a
detection threshold chosen to achieve a
certain value of constant-false-alarm-rate
(CFAR). lf the magnitude of an echo exceeds
the threshold, it is declared a detection. A
tracking algorithm associates successive
detections to form a track. The ability to
form tracks enables the radar sensitivity
to be increased by lowering the detection
threshold (thereby increasing the false alarm
rate), since only those detections that are
consistent with the established track are
displayed. ln this way, HFSWR conveys to
the user only those tracks corresponding to
real vessels. The track history also allows
the operator to visualize the activity of the
vessel and highlight anomalous or suspi-
cious behavior.
Track range
>200 nm day
140 nm night
I Commercial Cargo Vessels
Iracl( range
200 nm day
140 nm night
C
Trawler
Irack range
200 nm day
120 nm night
p Gillnetter
lracl( range
1 20 nm day
110 nm night
A Large CargoVessels
26 2012ISSUE2 RAYTHEONTECHNOLOGYTODAY
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Generally, at the lower end of the HF-band
the noise level increases at dusk and re-
mains high through the hours of darkness.
Also, during the hours of darkness there
are high levels of co-channel communica-
tion interference from distant HF users. As
a result, the radar operates with a reduced
range at night. Raytheon's HFSWR system,
however, is equipped with a number of
patented signal processing functions that
mitigate the effects of some of these inter-
ferences. Typical performance is illustrated
in Figure 4.
Since HFSWRs are tracking radars, object
classification based on track history is pos-
sible. From this track data, anomalistic
vessel behavior can be observed and used
to heighten awareness of suspicious activity
Examples of anomalistic behavior observed
by the radar are shown in Figure 5. ln the
first example, the vessel track was dropped
and subsequently re-acquired. Analysis of
the distance and time between the ter-
mination of one track and the initiation
of the new track indicated that the vessel
rapidly slowed down and remained station-
ary for approximately 10 minutes before
re-embarking on its journey. The system
highlighted this to the operator as being an
anomaly. This behavior was indicative of a
vessel that had transferred cargo to or from
another local vessel. ln the second example,
the radar tracks a vessel that left port head-
ing east-north-east. At a range of 70 nm
from shore, the vessel, now well outside
the range of traditional coastal surveillance
radars, made an abrupt 90 degree course
change and began to head in a north-
westerly direction, which in this case was a
maneuver that raised security concerns. An
intercept of the vessel was undertaken.
The high frequency surface wave radar
was developed by Raytheon to meet the
need for persistent surveillance of the stra-
tegically significant EEZ. lt was designed
to convey to the user high-quality tracks
corresponding to real vessels, allowing
anomalous or suspicious vessel behavior to
be readily identified and patrols dispatched
to investigate further. "
Tony Ponsford,
Rick McKerracher, Adeeb Khawja
Tony
Ponsford
Engineering
Fellow,
Technical
Director,
RCL
Dr. A.M. (Tony) Ponsford is a technical direc-
tor for Maritime Domain Awareness (MDA) at
Raytheon Canada Limited (RCL), specializing
in high frequency surface wave radar (HFSWR)
and integrated maritime surveillance (IMS)
technologies. Ponsford addresses the impor-
tance of putting the customer first and
foremost: "In my dual role of representing
Engineering and Business Development, I get
to r-neet customers and their scientific staff.
Together, we develop a solution to the problem
that they are facing. The solution
oftea encompasses engineering and financial
challenges, as weli as cultural. We then get to
transition the solution into a program that
meets the requirements and budget constraints
of the customer. It is rewarding when the rela-
tionships developed outlast the project."
Ponsford's MDA career started with his serving
in the Merchant Marine, where he worked with
Shell Tankers in developing concepts for MDA.
In the 1980s, working as a research associate at
the University of Birmingham, he initiated the
development of the HFSWR for persistent sur-
veillance of a nation's 200 nautical mile
exclusive economic zone (EEZ).In 1987, as
senior scientist, manager and technical director
for NORDCO's newly formed IMS business
unit, Ponsford established Canada's first
HFSWR test bed facility at Cape Bonavista in
St. |ohn's, Newfoundland. This effort eventually
progressed into the world's first shore-based,
real-time, EEZ surveillance sensor used to pro-
vide the continuous, all-weather tracking of
ships, icebergs and aircraft within the EEZ.
Ponsford collaborated with NASA, the
Canadian Space Agency and Western
University to develop a high frequency line-of-
sight radar to detect and track meteors. He also
designed HF radar systems for the U.S. govern-
ment to track cruise missiles and theatre
ballistic missiles.
"Engineering is a tough but rewarding profes-
sion," Ponsford relates. "Every day brings new
challenges. The most exciting aspect of this is
when you see one ofyour projects deployed
and working, with a happy customer. When
your customer gets promoted you know that
the system worked well."
Ponsford graduated with distinction from
Plymouth Navy College (UK). He earned a
bachelor's degree with first-class honors in
Maritime Technology from the University of
Wales Institute of Science and Technology. He
was awarded a doctorate in philosophy at the
University of Birmingham (UK) in recognition
of his pioneering work in HFSWR.
RAYTHEON TECHNOLOGY TODAY 201 2 ISSUE 2 27
Figure 5. Examples of anomalistic behavior
obseryedby an operational HFSWR.
I ) Oceangoing vessel stopped for l0 minutes,
60 nm from shore. 2) After leavingharbor, the
vessel taak an abrupt turtr at 70 nm from shore,
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