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Thursday 29 April 2004, 2 pm - 3.30 pm
(note different time & duration)
CSIRO Auditorium, Hobart
Dr Donald E Barrick
President
CODAR Ocean Sensors Ltd, Los Altos, CA
Co-presenter with Dr Steven R Ramp
Evolution, principles, and present status of
CODAR SeaSonde HF Radar family for surface current mapping and wave
monitoring
HF surface-wave radars (HFSWR) enjoy the unique features
that their long wavelengths reach distances above the ocean well beyond
the visible horizon when their antennas are mounted at sea level. The
long wavelength is also ideal for the Bragg scatter from surface gravity
waves that leads to the unambiguous extraction of surface currents and
wave information. But HFSWRs are not new – they have been around
since 1938, longer than the ubiquitous microwave radars that number
close to a billion. The impediment that has held back the proliferation
of HFSWR technology operationally has been the huge antenna sizes that
scale with the long wavelengths: an expanse of hundreds of meters of
unobstructed oceanfront is needed if "conventional beam-forming
wisdom" is followed. The CODAR invention I began at NOAA 30 years
ago aimed at replacing this costly obtrusive beast with an affordable
compact alternative that was suited for ocean surface monitoring. Our
SeaSonde products are the outcome of that effort. With 130 units now
deployed worldwide, this variety of HFSWR accounts for ~90% of HF radars
operating in the world today.
We examine the principles of scatter and operation, including our
departure from beam forming that eliminates their long, costly antennas
in favor of direction finding with a tiny unit that can be mounted on
a single post, out of reach. This comes at no accuracy reduction in
output data products. We show photos of installations all over the world
to give an idea of their deployment possibilities. We review the choices
of frequency bands that determine maximum range vs. spatial resolution,
so the user can select which meets the oceanographic needs for a given
region or investigation. Finally, we highlight some of the software
features that permit unattended, real-time operation from remote, difficult-to-access
locations and have allowed months and years of continuous data sets
to be gathered.
Donald
E. Barrick received his BEE, MSc, and PhD degrees in electrical engineering
from the Ohio State University, Columbus, OH. His Ph.D. research involved
interpretation of radar scatter from rough interfaces, including the
sea and planetary surfaces. He joined the staff of Battelle Memorial
Institute in Columbus OH where he led work in radar scattering and signal
processing as an Institute Fellow until 1972. During this period he
taught electromagnetics, radar, and communications theory at the Ohio
State University's Electrical Engineering Department as an Adjunct Professor.
From 1972-1983 he served as Chief of the Sea State Studies Division
(which he created) of the U.S. National Oceanic and Atmospheric Administration's
Wave Propagation Laboratory in Boulder, CO; there he developed compact
HF radar systems for real-time mapping of ocean currents and waves.
Since 1983 he has worked in industry, founding and heading CODAR Ocean
Sensors, Ltd. as President
His scientific
interests and experience include radio wave propagation, interaction
with, and scatter from the earth and sea at lower frequencies than microwave.
His engineering interests and activities have focused on development
of compact low-frequency radar systems with novel waveforms for remote
sensing, leading to several U.S. patents. His recent research has involved
use of HF-radar surface current data for improving ocean circulation
models, and use of normal modes to extend and improve nowcast maps of
HF radar data in bays and estuaries. Recent technology advances he has
spearheaded within COS involve buoy-based bistatic expansion of SeaSonde
coastal coverage; low-power, compact UHF bistatic radars for river flow
gaging; and a compact skywave HF radar design that can map ocean surface
conditions to 4000 km.
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