ARGO, Profiling Floats, and Iridium

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ARGO, Profiling Floats, and Iridium
Stephen C. Riser Dana Swift School of
Oceanography, University of Washington
acknowledgements to NOAA, ONR, NSF, NASA
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Profiling floatsa modern method of observing the
state variables of the ocean circulation.
Communications Service Argos ( 0.1 baud)
Floats routinely measure T and S as functions of
pressure, and absolute velocity at the parking
depth, usually 1000-2000 m. There is great
interest in expanding the capabilities of these
floats, including the addition of new sensors and
communication links and the ability to operate in
ice-covered regions. Issues power, weight,
unattended
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ARGO (not to be confused with Service Argos) is
an international program designed to deploy 3000
profiling floats in the world ocean, at
approximately 300 km resolution, forming the
first real-time in situ ocean observing
system Goal real-time T and S from the
subsurface ocean, globally, real-time All data
on GTS 4
The UW float group has built and deployed over
400 profiling floats in the past 6 years.
Components for these floats are purchased from
Webb Research Corp. construction and preparation
are done at UW.
ARGO
OKHOTSK SEA
JES
BLACK SEA
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Present status of ARGO 1244 floats deployed by
14 nations. The full, 3000 float array will be
implemented by the end of 2006.
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Present uses of data from profiling floats.
? Mapping regional circulation (JES N. Atlantic
Labrador Sea) ? Studies of convection (JES
Labrador Sea) ? Large-scale water masses,
circulation, and climate (ARGO) ? Studies of
mixing by hurricanes (N. Atlantic subtropics)
New features and technological improvements.

• Deep (2000 m) capability throughout the world
  ocean
• New sensors I (dissolved oxygen)
• New sensors II (low, high frequency acoustics)
• Under-ice capability
• ? Faster communications (Iridium)

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An example of data from profiling floats.
Each profile contains approximately 500 bytes of
data (3 variables x 2 bytes x 71 sample depths
engineering data) and requires 6-10 hours per
profile transmitting at the sea surface using the
Service Argo system.
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Argos antenna
CTD sensors
Inflatable bladder (inside cowling)
An example of a profiling float built at the
University of Washington
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Faster communcations.
Iridium/GPS patch antenna
We have built several floats that use the Iridium
satellite system instead of the usual Service
Argos. 2 floats were deployed in the Antarctic
Circumpolar Current south of New Zealand in
January 2003. They were configured as surface
drifters in order to assess the properties of
data transfer using the Iridium system. Results
show that data can be transferred using real
2-way communication at nearly 2400 bps. Mission
parameters can be changed in real-time.
Dial-up, X-modem Cost is comparable to,
perhaps somewhat greater than Service Argos.
Argos 500 byte transfer requires 9 hr
Iridium 20 Kb transfer requires
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Iridium drifter 006, 1/03 5/04
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Iridium modem (in this case a 9500 phone unit)
and GPS unit.
Drifter with Iridium unit installed.
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Data from Float 003 show consistent transfer of a
20 Kb file at rates of about 220 bytes/sec (red
data). Some handshaking is necessary at the
beginning and end of the data transmission. At
the end of each data transmission the float
uploads a command file (blue data) giving
instructions for the next profile.
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Usually a connection is established on the first
attempt in a few cases 2 or 3 attempts are
necessary. In most cases the full 20 Kb file can
be transferred in one connection.
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In general, we can obtain a GPS fix and transmit
a 20 Kb file in 10 minutes or less.
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SUMMARY.
Profiling float technology is advancing rapidly
there are many uses for the data from these
floats, including ocean/atmosphere/climate
studies using the global ARGO data. A major
improvement in these floats will come if and when
the present Service Argos communication system is
replaced with Iridium much faster data transfer
rates, and 2-way communication will be
possible. First deployment of ARGO/Iridium float
is anticipated in summer of 2004.