NOAA Technical Report NOS CO-OPS 057 

Ocean Systems Test and Evaluation Program 

noaa National Oceanic and Atmospheric Administration 

U.S. DEPARTMENT OF COMMERCE

National Ocean Service 

Center for Operational Oceanographic Products and Services

Redundant Communications 

Solutions for PORTS® Acoustic 

Current Profiler Installations 

Silver Spring, Maryland 

June 2010 
Ocean Systems Test and Evaluation Program 

ii 

Center for Operational Oceanographic Products and Services 

National Ocean Service 

National Oceanic and Atmospheric Administration 

U.S. Department of Commerce 

The National Ocean Service (NOS) Center for Operational Oceanographic Products and Services 

(CO-OPS) provides the National infrastructure, science, and technical expertise to collect and 

distribute observations and predictions of water levels and currents to ensure safe, efficient and 

environmentally sound maritime commerce. The Center provides the set of water level and tidal 

current products required to support NOS’ Strategic Plan mission requirements and to assist in 

providing operational oceanographic data/products required by NOAA’s other Strategic Plan 

themes. For example, CO-OPS provides data and products required by the National Weather 

Service to meet its flood and tsunami warning responsibilities. The Center manages the National 

Water Level Observation Network (NWLON), a national network of Physical Oceanographic 

Real-Time Systems (PORTS®) in major U.S. harbors, and the National Current Observation 

Program consisting of current surveys in near shore and coastal areas utilizing bottom mounted 

platforms, subsurface buoys, horizontal sensors and quick response real time buoys. The Center: 

establishes standards for the collection and processing of water level and current data; collects 

and documents user requirements, which serve as the foundation for all resulting program 

activities; designs new and/or improved oceanographic observing systems; designs software to 

improve CO-OPS’ data processing capabilities; maintains and operates oceanographic observing 

systems; performs operational data analysis/quality control; and produces/disseminates 

oceanographic products 

Ocean Systems Test & Evaluation Program 

The CO-OPS Ocean Systems Test and Evaluation Program (OSTEP) facilitates the transition of 

new technology to an operational status, selecting newly-developed sensors or systems from the 

research and development community and bringing them to a monitoring setting. OSTEP 

provides quantifiable and defensible justifications for the use of existing sensors and methods for 

selecting new systems. The program establishes and maintains field reference facilities where, in 

cooperation with other agencies facing similar challenges, devices are examined in a nonoperational field setting. OSTEP evaluates sensors, develops quality control procedures, and 

generates maintenance routines. Rigorous, traceable calibrations and redundant sensors assure 

the quality of the reference systems used in the field. 
NOAA Technical Report NOS CO-OPS 

Ocean Systems Test and Evaluation Program 

U.S. DEPARTMENT OF COMMERCE 

Gary Locke, Secretary 

National Oceanic and Atmospheric Administration 

Dr. Jane Lubchenco 

Undersecretary of Commerce for Oceans and Atmosphere and NOAA Administrator 

National Ocean Service 

David Kennedy, Assistant Administrator 

Center for Operational Oceanographic Products and Services 

Richard Edwing, Director 

Redundant Communications 

Solutions for PORTS® Current 

Profiler Installations 

Warren Krug 

Mark Bushnell 

Edward Roggenstein 

Robert Heitsenrether 

June 2010 
Ocean Systems Test and Evaluation Program 

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NOTICE 

Mention of a commercial company or product does not constitute an 

endorsement by NOAA. Use of information from this publication for 

publicity or advertising purposes concerning proprietary products or the 

tests of such products is not authorized. 
v 

TABLE OF CONTENTS 

ACKNOWLEDGMENTS ............................................................................................................ vii 

EXECUTIVE SUMMARY ........................................................................................................... ix 

1.0 INTRODUCTION/BACKGROUND .................................................................................. 1 

1.1 Statement of the Issues to be Addressed ....................................................................... 3 

2.0 PORTS® DATA COMMUNICATIONS IMPROVEMENTS ............................................ 5 

2.1 DCP for Acoustic Current Profiler Installations ........................................................... 5 

2.2 Wireless IP Modems for ATON Acoustic Current Profilers Installations ................... 7 

2.3 Iridium Modems for ATON Acoustic Current Profiler Deployments .......................... 8 

2.4 Dial-up Iridium Modems for Stations Beyond Common Terrestrial Communications 

Links ............................................................................................................................. 9 

2.5 GOES DCP Command via Sutron SBIR .................................................................... 10 

3.0 GENERAL HANDOFF TO OPERATIONS ..................................................................... 13 

3.1 Dial-up Iridium Modems Handoff to Operations ....................................................... 13 

3.2 ISD Responsibilities Handoff ..................................................................................... 13 

3.3 OD Responsibilities Handoff ...................................................................................... 13 

4.0 CONCLUSIONS/RECOMMENDATIONS ...................................................................... 15 

REFERENCES ............................................................................................................................. 19 

ACRONYMS 

vii 

ACKNOWLEDGMENTS 

We are grateful to Steve Gill (NOS/CO-OPS/Staff), Tom Mero (NOS/CO-OPS/Engineering Division), 

Chris McGrath (NOS/CO-OPS/Engineering Division), and Darren Wright (NOS/CO-OPS/Staff) for their 

review and valuable comments. 

The authors would also like to thank our technical writer/editor, Helen Worthington (REMSA, Inc.) for 

her assistance in preparing this report. .

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EXECUTIVE SUMMARY 

The Center for Operational Oceanographic Products and Services (CO-OPS) is committed to 

providing products and services that support safe and efficient marine transportation, sound 

environmental management, and effective emergency planning. Numerous CO-OPS products 

are part of the Physical Oceanographic Real-Time System (PORTS®). The PORTS® network 

contains a suite of instruments that measure and disseminate observations of environmental and 

meteorological parameters and has become a major decision support tool that integrates real-time 

environmental observations, forecasts, and other geospatial information. 

Reliable data communication paths are critical to maintaining the high quality products that 

make up the PORTS® network. CO-OPS depends upon telephone lines, line-of-sight (LOS) 

radios, wireless Internet protocol (IP) and Iridium modems, as well as Geostationary Operational 

Environmental Satellites (GOES), to transmit data that serve as the backbone of PORTS®

products. Most systems use at least one of two or more telemetry methods to ensure that realtime data reach CO-OPS servers. However, most acoustic current profilers within the PORTS®

system do not have a redundant communication path because the message sizes are both large 

and frequent (transmitted every six minutes). Of the 38 acoustic current profilers that CO-OPS 

maintains, most contribute to PORTS® data, including the 15 that reside on aids to navigation 

(ATON) buoys. 

Although installing redundant communications for all acoustic current profilers is ideal, a more 

immediate goal is to implement more robust communications on ATON profilers. The Ocean 

Systems Test and Evaluation Program (OSTEP) has several projects underway, some of which 

will help to achieve this goal by improving the data communications for both ATON and cabled 

acoustic current profilers. These projects include integrating the Sutron Xpert 9210B data 

collection platform (DCP) with Sontek and RDI acoustic current profilers, installing the Xpert 

DCP in the Nortek ATON profiler electronics box, using Iridium or wireless IP modems on 

ATON profilers, and developing the DCP Command receiver using the GOES system. These 

projects and technologies provide multiple options for redundant communications, allowing COOPS to use the technology that best fits the specific need, while maintaining high quality 

PORTS® products. 

Implementation of these projects in appropriate situations will enhance PORTS® products; 

however, other challenges remain. Data sets of the ATON acoustic current profilers are too large 

for the bandwidth available on GOES, so efforts are underway to optimize instrument 

configurations that reduce the size of data sets. While existing products will not be affected by 

transmitting messages in subsets, making it work seamlessly with the CO-OPS ingestion process 

will take considerable effort. 
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Technology is changing rapidly; therefore, ensuring that CO-OPS uses the best and most costeffective solutions for PORTS® data communications is a tremendous challenge. It requires 

flexibility and constant attention to make sure that products and services keep pace with the 

technology advances and the efficiencies they can provide. For example, two-way 

communications and supporting technologies are paramount to keeping pace with maintenance 

requirements for remote stations. Iridium modems can potentially play a key role in meeting 

these requirements, not only for acoustic current profilers, but also for other sensors, especially if 

the cost of Iridium continues to decline. Herein lies a key reason for CO-OPS to support the 

NOAA Office of Policy, Planning, and Evaluation effort, headed by Steve Piotrowicz, to secure 

a dedicated Iridium service similar to that of the Department of Defense (Personal 

communication May 2009). 

Implementation of the recommendations and project improvements described in this report is 

critical to maintaining accurate and reliable information flow to the PORTS® network and brings 

CO-OPS a step closer to achieving the overall goal of establishing redundant data 

communication paths for acoustic current profilers. 
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1.0 INTRODUCTION/BACKGROUND 

The Center for Operational Oceanographic Products and Services (CO-OPS) oversees an 

extensive network of instruments that collect, analyze, and disseminate integrated oceanographic 

and meteorological data. These data result in products that contribute to safer shipping and 

boating, more efficient port operation, more thorough emergency planning to ensure the safety of 

coastal residents, and improved environmental planning and protection. Several of these data 

products offer real-time, 24/7 data to shippers, port operators, emergency planners, coastal 

managers, and others throughout the U.S. and are part of the CO-OPS Physical Oceanographic 

Real-Time System (PORTS®). 

PORTS® consists of a suite of instruments that measure and disseminate observations of water 

levels, currents, salinity, and meteorological parameters (winds, atmospheric pressure, air and 

water temperatures). Ultimately, PORTS® serves as a major decision support tool that improves 

the safety and efficiency of maritime commerce and coastal resource management through the 

integration of real-time environmental observations, forecasts, and other geospatial information. 

Instruments that collect these data are strategically positioned at 20 PORTS® systems, with 183 

stations located at 50 of the Nation’s largest ports. 

The transmission of data from PORTS® stations can occur in several ways, depending upon the 

size of the data messages and how frequently transmission is required. Methods of data 

transmission used include wireless Internet protocol (IP), Iridium, and line-of-sight (LOS) radio 

modems, telephone lines, and Geostationary Operational Environmental Satellites (GOES). 

The importance of reliable data communications for PORTS® cannot be understated. The 

PORTS® network of instruments depends on high quality communications to collect and 

distribute data, and many systems include redundant communication paths to ensure that 

PORTS® data are available to users. When communications fail, CO-OPS products cannot be 

delivered to those who depend on them for decision support. There are numerous points along 

the telemetry pathway where failure can occur—from the first data point collected through 

product delivery to customers. Each instrument and process occurring between these two paths 

must work properly for successful data transmission to occur. 

Failures are often attributed to the data delivery part of the process; however, a study of the 

reasons for system downtime revealed that data delivery failures happened because the telemetry 

system did not transmit, and there was no secondary or redundant system to intervene. An April 

2006 report funded by the National Oceanographic Partnership Program (NOPP) and issued by 

the Johns Hopkins Applied Physics Laboratory (Nichols et al. 2006) stated: 

Experience in recent coastal predictive skill experiments 

on both the east coast and the west coast have relied 

heavily on HF [high frequency] radar surface currents for 
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adaptive sampling. HF radar systems consist of a series of 

remote shore sites with HF radio transmitters and 

receivers. In both cases, the greatest source of system 

downtime was traced not to the high technologies of the 

HF radar system, the computer analysis at the remote 

shore site, or the product production at the main control 

center and subsequent distribution via the web on the 

internet. The biggest source of downtime was the relative 

low technical solutions required for communications from 

a remote shore site to a central internet-equipped facility. 

Standard phone lines with dial-up modems and LOS radio 

modems were used. It was found that the most costeffective means to improve system uptime was to add a 

redundant communication path to each remote location. 

This way, when one system goes down, the other is still 

available for remote access. 

Current measurement systems are among those at greatest risk for data delivery failure because 

they often lack redundant communications. Fifteen acoustic current profilers mounted on aids to 

navigation (ATONs) provide current data within the PORTS® network. An additional 23 cabled 

systems also provide current measurements for PORTS® at some of the more than 200 National 

Water Level Observation Network (NWLON) stations. ATON acoustic current profilers 

generate large and frequent data messages, (every six minutes), making redundant 

communications prohibitively expensive, depending upon the telemetry method used. Also, the 

PORTS® interface board (Sprenke board) cannot manage more than one method of 

communication. If communication from the acoustic current profiler fails at any single point 

along the data transmission path, data transmitted during that time are lost. Determining the 

specific failure point can be difficult; however, implementation of a redundant (or at least a 

secondary) communication path seems to be the best way of preserving valuable PORTS® data. 

Absent a redundant telemetry method, implementation of more robust communications for 

ATON acoustic current profilers should be an immediate goal to ensure high quality PORTS®

data. 

In July 2008, the PORTS® manager submitted a Razor request to begin implementation of 

redundant communications methods for acoustic current profilers. Razor, the CO-OPS software 

configuration management system, provides for process management, issue/problem tracking, 

and version control-and-release management. The goal of the request is to augment the 

robustness of data communications within the PORTS® system. The request outlines the project 

deliverables, timeframe, and resources needed for successful implementation. The first 

deliverable includes an assessment of existing capabilities. The next is to identify stations or 

sensors within PORTS® that do not have a redundant method of data transfer. If possible, 
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stations/sensors without a redundant method of transferring data should receive an additional 

communications method. The next deliverable is development of the capability to transmit 

acoustic current profiler data over GOES, and finally, to add that capability to all real-time 

acoustic current profilers (i.e. planned deployments outside of PORTS®). 

Resources throughout each CO-OPS division are required to implement this Razor project. For 

example, over the six-month project duration, staff/Engineering Division (ED) in Silver Spring, 

MD will perform an assessment of existing capabilities and identify sensors without a redundant 

method of transferring data. OSTEP will develop the current profiler data collection capability 

via the Sutron Xpert data collection platform (DCP), as well as a program to transmit reduced 

current profiler data format. The Information Systems Division (ISD) will develop the capability 

to receive current profiler data over GOES in a reduced data format. The Oceanographic 

Division (OD) Coastal and Estuarine Circulation Analysis Team (CECAT) will develop a 

reduced data format for current profiler data to transmit over GOES. 

The rapid development of data transmission technology requires the oceanographic community 

to examine potentially more reliable and less expensive ways to deliver products to consumers of 

PORTS® data. As a result, CO-OPS also faces the reality of the extensive organizational 

coordination required to stay abreast of the latest technology. Coordination and communication 

among CO-OPS divisions are crucial to the generation of high quality PORTS® data products. 

Reliable data communication paths are equally as vital to the delivery of those products. Thus, 

improving the reliability of data communications is a high priority for OSTEP in FY 09 and is 

evidenced in several projects already in progress. For example, OSTEP is pursuing a transition 

away from Sprenke boards on cabled acoustic current profilers and is instead adapting the Sutron 

Xpert DCP (which allows for multiple communication methods) for use within the electronics 

box. OSTEP has also tested Iridium Short Burst Data (SBD) modems for communication with 

remote sensors. Implementation of these projects will result in the replacement of LOS radios 

with the more robust wireless IP and Iridium modems. These and several other projects are 

complementary and parallel in purpose to the previously mentioned Razor request. The 

following sections outline the status of and strategy for these projects, as well as the resources 

and personnel required to reach the ultimate goal of providing redundant communication paths 

for acoustic current profilers. 

1.1 Statement of the Issues to be Addressed 

CO-OPS presently uses wireless IP modems as the communication method for most cabled 

acoustic current profiler installations. The modem is connected to a PORTS® interface board 

(Sprenke board), which provides power and communications to the profilers. Since this method 

lacks the capability to add a second communication path or to store data outside of the profiler, 

the addition of a DCP to the PORTS® acoustic current profiler system would provide these 

capabilities along with other possible improvements, such as the addition of a wind sensor. 
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LOS radio modems provide a reliable communication path and can be robust at short distances. 

However, since over time PORTS® users have requested information about currents further from 

the shore stations, the distances between the shore station and buoys in many cases have 

increased. Sometimes as a result, these longer distances have exceeded the design limits of LOS 

radios. As we anticipate the future needs of PORTS® users, it is essential to identify more robust 

methods of transmitting data. 

PORTS® ATON acoustic current profilers record 20 current profiles in 1-meter (m) bins. 

Although some ATONs are located in deeper water, many collect profiles in 10 m of water or 

less. This not only results in unusable and meaningless data profiles that exceed the water depth, 

but it also requires more power and incurs greater costs by generating more frequent 

maintenance visits. Therefore, it is important to optimize acoustic current profilers’ 

configurations to improve the reliability of data transmission, collecting only essential 

information, while ensuring that PORTS® products remain unchanged. 
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2.0 PORTS® DATA COMMUNICATIONS IMPROVEMENTS 

The requirement for more robust PORTS® data communications is clear. PORTS® users and 

society as a whole derive numerous benefits from these products, and product improvement is 

essential to maintaining the quality and value of the PORTS® suite of instruments to the user 

community. To address the need for increasing the robustness of data transmission, especially 

for real-time current observations, CO-OPS has undertaken several efforts that improve data 

communications, including: 

 DCP for acoustic current profiler installations 

 Wireless IP modems for ATON acoustic current profiler installations 

 Iridium modems for ATON acoustic current profiler deployments 

 Iridium modems for stations beyond common terrestrial communications links 

 GOES DCP Command capability via Sutron SBIR 

The status and plans for each of these efforts are detailed in the following paragraphs. 

2.1 DCP for Acoustic Current Profiler Installations 

In August 2005, CO-OPS provided funds to Sutron Corporation to develop code supporting the 

ingestion of RDI acoustic Doppler current profiler data, and eventually expanding the effort to 

include Sontek acoustic current profilers. As a result, OSTEP integrated a Sutron Xpert 9210B 

DCP with both the Sontek and RDI acoustic current profiler systems. The DCP polls the profiler 

every six minutes, stores these full data sets in a daily file, as well as a file that the PORTS® data 

acquisition system (DAS) polls by a using one of two or more methods of communications (LOS 

radio, wireless IP, or Iridium modem, telephone, or an Ethernet connection). These daily files 

can be downloaded each night as a backup to the already transmitted data. The DCP can store up 

to four months of data. In addition to the acoustic current profiler data set, the DCP can also 

send back the battery voltages of the DCP, profiler, and communications equipment, as well as 

those of other sensors, depending on the amount of data space available. A test of the system 

using a Sontek side-looking profiler is now underway, and it will soon be installed at a field test 

site. In the future, the system will be able to transmit a subset of the data every six minutes via 

GOES, however, ED and OD must determine the subset of data that can be transported (the 

entire data stream is too large for a GOES message), while ensuring that existing products 

remain unchanged. 

When implementing new and improved data communication methods, it is crucial to optimize 

the format of the data to be transmitted to ensure efficient delivery and decrease the likelihood of 

communication failure. Reducing the size of a data message, if possible, can result in more 

efficient, and in some cases less costly, data telemetry. 
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The size of the data collected by PORTS® ATON acoustic current profilers can be significantly 

reduced at most deployment locations. Currently, all PORTS® ATON profilers are configured to 

collect data in 1-m depth bins and record data from 20 bins, which is transmitted and stored in 

CO-OPS data bases. However, water depth at most ATON acoustic current profiler deployment 

locations is significantly less than 20 m, particularly at various Chesapeake Bay and Gulf of 

Mexico PORTS® locations. Also, when an acoustic current profiler is deployed on an ATON 

using the “clamparatus” device, the transducer head is located approximately 2 m below the sea 

surface (Bosley et al. 2005) and the instruments have a 0.4-m blanking distance, i.e., the first 

good depth bin of current data will be approximately 2.4 m below the water column. 

Consequently, good current data can only be collected at most deployment locations over a depth 

range significantly less than 20 m, and data recorded in extra bins that extend beyond the sea 

floor are meaningless, typically containing noise that results from the bottom-reflected acoustic 

current profiler signals. 

Figure 1 contains plots generated using the CO-OPS C-MIST tool, which show contours of 

ATON acoustic current profiler data collected at Chesapeake Bay PORTS® ATON at York Spit; 

(a) echo intensity (dB), and (b) current magnitude (cm/s). In both plots, the bottom of the water 

column is significantly shallower than the range of the last recorded depth bin. These data 

provide an example of an operational PORTS® ATON acoustic current profiler system that is 

currently recording and transmitting extraneous data that contain only noise—no meaningful 

current measurements. 

As part of the communication improvements proposed in this document, PORTS® ATON 

acoustic current profiler configurations should be optimized to reduce the size of data recorded, 

including only depth bins that contain meaningful current data. This involves determining mean 

water depth at a deployment site along with a typical tidal water level and range, and then 

changing the bin number setting in the acoustic current profiler configuration file accordingly. 

Reducing the size of transmitted ATON profiler data requires minimal effort during deployment 

planning. Such action can significantly improve not only the communication efficiency but also 

the capability of data access and analysis tools, such as C-MIST, and can also increase storage 

capacity of CO-OPS data bases. 
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Figure 1. Sample contour plots of data collected by a Chesapeake Bay PORTS®

ATON acoustic current profiler at York Spit (ID: cb0201). Data were accessed and 

plots generated using CO-OPS C-MIST online analysis tool; (a) beam 1 echo intensity 

and (b) current magnitude contour. In both records, it is clear that the sea bottom is 

significantly shallower than the range of the final recorded depth bin (bin 20), 

indicating that extraneous data, beyond the range where meaningful current 

measurements can be obtained, were recorded, transmitted, and stored in CO-OPS 

databases.

While reducing the size of the data packet can improve transmission efficiency, reconfiguring the 

way that GOES messages are transmitted could also improve the ability to transmit 6-minute 

data. To accomplish this, the National Environmental Satellite, Data, and Information Service 

(NESDIS) anticipates reducing the guard band between each GOES channel to double the 

number of GOES IDs available. This may allow CO-OPS to access 1200-baud assignments with 

6-minute cycles, permitting the transmission of an entire current profile. Although this has not 

yet been accomplished, GOES capacity and capability indicate that it is possible. NESDIS is 

ultimately responsible for granting permission and implementing such changes. 

2.2 Wireless IP Modems for Aton Acoustic Current Profilers Installations 

Another improvement underway is OSTEP’s and the Chesapeake Instrument Laboratory’s 

(CIL’s) work on installing an Xpert 9210 DCP in the ATON acoustic current profiler electronics 

box. This installation eliminates the need for a shore station and the LOS system. Stevens 

Institute (Jeremy.Turner@ Stevens.edu, 201-216-5223) was the first to employ this method, but 

results were mixed. The system worked as expected, but the deployment time was brief due to 

battery life limitations imposed by the modified setup. In the Stevens design, raw data were sent 

to a computer via the wireless IP modem and then decoded and processed. In the CO-OPS 

system, the goal is for the DCP (presently located at the shore station) to be installed on the 

buoy. This method allows the local storage of data, which can then be used to backfill missing 
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data caused by communications or ingestion problems, and permits optimized data decoding and 

transmission, which reduces power consumption. 

OSTEP has purchased a set of lithium battery packs that will extend the deployment length to six 

months or more, depending on the number of packs installed. The CIL has also obtained a newer 

Raven EV-DO modem to replace the standard Raven IP modem used at the Stevens Institute 

system. Unfortunately, recent testing indicates that the newer modem seems to require the same 

or more power. A prototype system is currently being tested at the CO-OPS Chesapeake facility. 

There is still an opportunity to consider alternative decoding schemes (perhaps using Nortek 

Aquapro software as the core decoder) to reduce power consumption. For example, raw binary 

data that are currently decoded in DCPs could be transmitted and then decoded later in the data 

path. Such decoding schemes would need to be developed and implemented in Silver Spring. 

Verizon will introduce the next generation of wireless IP modems (fourth generation or 4G) on a 

limited basis in 25-30 U.S. cities at the end of 2010. These modems will be capable of downlink 

data rates of up to 200 megabytes per second and uplink speeds of 50 megabits per second, and 

the system will also be fully IPv6 compliant. Verizon’s tests in urban settings resulted in 

downlink speeds of 50 megabits per second and 25 megabits per second for uplinks. The present 

3G system has a downlink speed of 14 megabits per second and an uplink speed of 5.8 megabits 

per second. CO-OPS/ED has discussed beta testing 4G stand-alone modems at selected locations 

with Verizon and Sierra Wireless (equipment manufacturer). 

2.3 Iridium Modems for ATON Acoustic Current Profiler Deployments 

Due to their small size and low power requirements, the Iridium Short Burst Data (SBD) 

modems (9601-D SBD data-only modems from NAL Research) are ideally suited as a reliable 

communication path for acoustic current profilers. The 9601-D is a single purpose modem that 

provides limited two-way communications. It quickly and automatically registers with the 

Iridium satellites when powered up and is designed to permit power cycling of the unit. This 

feature is important because it extends battery life by using power only when needed for data 

transmission. SBD modems produce packetized transmissions that have a maximum SBD 

Mobile Originated message (MOM) size of 340 bytes and SBD Mobile Terminated message 

(MTM) size of 270 bytes. The Iridium system requires a portion of the message size (e.g. time 

of transmission, modem IMEI, transmission start and stop); the rest of the packet is used for data. 

CO-OPS currently has two SBD modems in service that provide 6-minute data from NWLON 

stations located in Guam. Additionally, one SBD modem installed on an ATON buoy 

transmitted acoustic wave acoustic current (AWAC) data twice hourly for 10 months. SBD test 

results from buoy- and land-based platforms demonstrate a >99.7% successful transmission of 

data. 

MTM SBD (two-way) should result in a similar transmission success. Power cycling of the 

modem is not affected, since the Iridium system holds SBD MTM until the intended modem 
Ocean Systems Test and Evaluation Program 

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registers with the satellite network. The worst case delay with the transmission to a buoy would 

be six minutes. This small packet communication would be formatted and could easily be 

adapted for Iridium in conjunction with the GOES DCP Command (see section 2.5). SBD 

enables limited two-way transmission that offers a reliable and robust communications link with 

remote stations. 

In the spring of 2009, the USACE Cold Regions Research and Engineering Lab (CRREL) 

provided funds to Sutron for development of DCP Command-based MTM SBD to control the 

Sutron monitor series of DCPs, which the CRREL use in remote environmental monitoring 

applications. CO-OPS collaborated to provide a test modem and other assistance. Sutron 

demonstrated full remote command of the DCP and is currently adapting this capability to 

operate using the Xpert series of DCPs. Once DCP Command is available, OSTEP will test and 

demonstrate it on our development stations at the FRF in Duck, NC, which provides an 

opportunity to test DCP Command protocols before the GOES DCP Command becomes 

available. 

When an Iridium modem is implemented in an ATON acoustic current profiler system, 

communications will improve; however, because the large power requirements of ATON current 

profilers remain a challenge, CO-OPS needs to continue collaboration with acoustic current 

profiler manufacturers on system enhancements that increase battery capacity. Iridium presents 

an additional limiting factor due to the cost of transmission. NOAA’s primary source of Iridium 

data service is through commercial providers. 

CO-OPS has limited access to Iridium service provided through the Department of Defense’s 

(DoD’s) dedicated service. The major advantage for DoD is in the unlimited data plans. The 

DoD costs are estimated at $350 per month per unit or $4,200 per year per unit. CO-OPS’ best 

case scenario for the commercial option would cost more than twice that amount per year per 

unit. For 6-minute ATON transmissions, a DoD-like agreement would offer the best value from 

a set operational price point perspective. Steve Piotrowicz from NOAA’s Office of Policy, 

Planning, and Evaluation has been working to secure a DoD-like agreement for NOAA and/or 

the National Science Foundation (NSF) (Personal communication, May 2009). 

The number of transmissions and amount of data being transmitted in a particular deployment 

must be identified to determine which Iridium option would be the least expensive. For 

example, the DoD Iridium services have a comparatively higher charge per month if few data are 

transmitted; however, DoD unlimited data plans could represent a significant savings if large 

data quantities were transmitted. 

2.4 Dial-up Iridium Modems for Stations Beyond Common Terrestrial 

Communications Links 

Dial-up Iridium modems (A3LA-D from NAL Research) have been successfully deployed in 

remote test systems located at Wake Island and Guam in the Pacific Ocean and Mona Island, 
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Puerto Rico. Since other back-up communication options either proved to be cost prohibitive, 

physically impossible, or unreliable due to the remoteness of these locations, Iridium offered the 

only alternative cost-effective option for a back-up communications system in these and other 

remote locations. The polar orbit of Iridium satellites provides the true global coverage that is 

essential in high and extremely high latitudes, where the angle required to transmit a signal 

makes GOES transmissions impossible. Iridium also provides an option where phone or cellular 

service is spotty or non-existent. The best service provider package for Iridium dial-up is 

commercial, with a rate of $14 per month per unit, plus a per-byte data transmissions fee and the 

cost of an international call whose rate depends on the phone plan selected. The DoD cost is 

$100 per month. Since the modem is not actively being used most of the time, commercial 

service is the least expensive option. 

The Iridium dial-up modem has proven to be reliable. The one noted issue is an intermittent 

inability to establish the connection. From all indications, the problem is at the interface of the 

phone lines to the Iridium gateway. CO-OPS has a development IP address for Iridium at the 

Chesapeake facility and has also secured commercial Iridium service for that address to begin 

direct IP transmission testing. Any development on the commercial Iridium service can be 

transferred to our DoD-serviced modems. The connection issue will hopefully be resolved in the 

near future. 

Unlike the SBD-only modem, the dial-up modem provides a number of options. It can function 

as an SBD modem with a 1960-byte MOM and 1850-byte MTM capability, a standard modem 

(i.e. dial-up), Direct IP, and RUDICS. It can also serve as a telephone with an adaptor. This 

modem provides true two-way communications. Software such as Procomm and Xterm can be 

used to communicate with the DCP, including the transfer of software and data files to and from 

the DCP. However, the dial-up modem is twice the size and cost of the SBD modem and 

consumes three times the power, making it impractical for locations where space is limited 

and/or power is constrained by the lack of solar charging. 

The next generation of dial-up modems is now available and features an integrated power supply 

for 3.5-36 Vdc with two external LEDs added to indicate power and signal strength. The modem 

offers full broadband capability for use with new satellites; however, it also consumes one-third 

more power than the model it replaces. 

2.5 GOES DCP Command via Sutron SBIR 

Sutron Corporation received a Small Business Innovation Research (SBIR) Phase I grant to 

develop a robust link from GOES to the DCP (SBIR Abstracts 2007) with the following 

attributes: 

 Immune from local interference 

 Low power consumption 

 Low cost 
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 Reliable 

 Provides useful amount of data with minimum wasted bandwidth 

 Meets NTIA (National Telecommunications and Information 

Administration) regulatory requirements that ensure that NESDIS 

will retain the frequency assignment for DCP Command protocol 

 Designed to work with low-cost antennas 

 Contains capability of adding adaptive filtering techniques without 

further hardware changes 

Sutron has now received and completed an SBIR Phase II grant and has demonstrated successful 

two-way communications through the existing GOES satellite transponder. As a result, the 

Satellite Telemetry Interagency Working Group (STIWG) continues to solicit contributions to 

support the development of a prototype ground system at Wallops Island, Virginia. 

Approximately $50K of the $100K needed to build the prototype has been obtained. The upfront 

costs associated with the development of DCP Command are more than offset by the ultimate 

realization of almost no recurring costs (other than those already associated with the DCS 

operations). In contrast, Iridium has low start-up costs, but the guaranteed monthly recurring 

costs remain. STIWG representatives (and presumably the associated agencies), the NOAA 

SBIR community, and GOES DCS staff all fully support the implementation of DCP Command.  

Ocean Systems Test and Evaluation Program 

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3.0 GENERAL HANDOFF TO OPERATIONS 

Project implementation results in moving from the test and evaluation phase to operations. The 

transition to operations is a critical time and the handoff must be seamless to ensure that data 

products continue to be available. The dial-up Iridium modem project described in section 2.4 is 

now ready for handoff to operations. Although the present test sites do not involve acoustic 

current profilers, Iridium is a viable solution in certain circumstances. The following paragraphs 

describe tasks that are critical to becoming operational, whether the Iridium modem is associated 

with an acoustic current profiler or a water level sensor. 

3.1 Dial-up Iridium Modems Handoff to Operations 

Field tests of dial-up Iridium modems have been successful and are now ready for transition 

from test to operational status. The next step is to select a person from the CIL to be in charge of 

the handoff to operations. Additionally, the responsibility for billing must be transitioned to 

FOD. The responsible person (s) must be designated as administrator (s) on the commercial 

account so that they can make changes or additions to the account as required by the service 

provider. Once these contacts are established, a letter informing NAL Research of the change 

must complete the transition. This releases the modems from ED to operations personnel and 

account billing to FOD. 

3.2 ISD Responsibilities Handoff 

OSTEP envisions continued use of wireless IP modems and/or telephone lines to provide the full 

acoustic current profiler data sets. The introduction of alternative GOES or Iridium SBD data 

subsets requires data ingestion and processing that have a different format, presenting new 

challenges for ISD. Once OSTEP provides the new data formats, ISD will be responsible for 

invoking new routines when toggling to the alternative communications methods that utilize the 

data subsets, as well as integrating them into existing products. 

3.3 OD Responsibilities Handoff 

Alternative communications methods such as GOES and Iridium SBD have a limited bandwidth 

and can only provide data subsets (rather than the full acoustic current profiler data sets now 

collected). These data subsets will be carefully chosen so that CO-OPS products remain 

unchanged. OD must work closely with OSTEP and ISD to ensure that these products remain 

robust and are backed by sufficient QA/QC. 

Ocean Systems Test and Evaluation Program 

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4.0 CONCLUSIONS/RECOMMENDATIONS 

Reliable data communications are critical to ensuring that PORTS® data are available to those 

who depend upon them for safe and efficient navigation and emergency management. To 

achieve maximum reliability, CO-OPS requires redundant systems for transmitting data from 

acoustic current profilers in case of primary communication system failure. However, acoustic 

current profilers have not had redundant systems in the past for several reasons, among which are 

large data sets, frequent transmissions, and the use of equipment that does not accommodate 

multiple communication methods. 

In summary, OSTEP supports the Razor request submitted in July 2008 and, through this report, 

responds to it by documenting the status of OSTEP efforts to increase the robustness of PORTS®

data communications, as well as the ultimate goal of implementing redundant communications 

for PORTS® acoustic current profilers. The projects described in this report offer creative ways 

to customize potential improvements to deliver PORTS® data in the most cost-effective and 

efficient way. OSTEP offers several conclusions and recommendations that may help in the 

effort to do so. 

Conclusions 

 The selection of a primary and an alternate method of communication 

for acoustic current profilers depends upon several factors, including 

access to power, sensor location (remote or not), and type of sensor 

(ATON versus bottom-mount or side-looking). 

 We have demonstrated that acoustic current profilers can be interfaced 

to Sutron Xperts. 

 No product degradation will occur because of our conclusions or 

recommendations. 

 Most communication systems do not have enough bandwidth to send 

an entire data set; therefore each message must be reduced in size 

without loss of essential data. 

 Potentially, the number of GOES channels could be doubled if the 

guard band (or the spaces between each channel) is tighter. This 

would free a lot of transmission space, and although it has not yet 

occurred, the capacity and capability indicate that it is possible. GOES 

transmits 300-baud messages for hourly and for the 6-minute 

transmissions. GOES can also transmit 1200-baud messages; 

however, no 1200-baud, 6-minute transmit interval allocations have 

yet been assigned. 
Ocean Systems Test and Evaluation Program 

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 Technology is rapidly changing. The changes create a challenge to 

ensure that we are using the best and most cost-effective solutions for 

PORTS® data needs. 
Ocean Systems Test and Evaluation Program 

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Recommendations 

 Support and Implement the Five Suggested Communications 

Improvements in Section 2.0 of this Document 

Implementing the improvements described in section 2.0 as soon 

as possible will help us to achieve our goal of more robust 

communications for PORTS® acoustic current profiler 

installations. 

 Support Acquisition of a Dedicated Iridium Service for NOAA 

CO-OPS should support the NSF/NOAA effort, headed by Steve 

Piotrowicz of NOAA’s Office of Policy, Planning, and Evaluation, 

to secure communication services that would provide two-way, 

real-time communications from multiple platforms by using a 

dedicated Iridium service for NOAA.

Ocean Systems Test and Evaluation Program 

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REFERENCES 

Nichols, R.A. et al. April 2006. An integrated wireless coastal communications network, Johns 

Hopkins University Applied Physics Laboratory. 

Bosley, Kathryn Thompson, PhD; Chris McGrath, Jennifer P. Dussault; Mark Bushnell, Michael 

J. Evans, Geoffrey W. French, Karen Earwaker. May, 2005. Test, evaluation, and 

implementation of current measurement systems on aids-to-navigation, NOAA Technical Report 

NOS CO-OPS 043, Center for Operational Oceanographic Products and Services, NOS NOAA, 

Silver Spring, MD. 

U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration, 

Small Business Innovation Research Program, FY2007Abstracts.pdf. [Internet].
Ocean Systems Test and Evaluation Program 

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Ocean Systems Test and Evaluation Program 

Acronyms 

ATON aid to navigation 

CECAT Coastal and Estuarine Circulation Analysis Team 

C-MIST Currents Measurement Interface for the Study of Tides 

CO-OPS Center for Operational Oceanographic Products and Services 

CRREL Cold Regions Research and Engineering Laboratory 

DAS data acquisition system 

DCP data collection platform 

DCS data collection system 

DoD Department of Defense 

ED Engineering Division 

FOD Field Operations Division 

GOES Geostationary Operational Environmental Satellites 

HF high frequency 

IMEI International Mobile Equipment Identity 

IP Internet protocol 

ISD Information Systems Division 

LED light-emitting diode 

LOS line-of-sight 

LRGS local readout ground stations 

MOM mobile-originated message 

MTM mobile-terminated message 

NESDIS National Environmental Satellite, Data, and Information Service 

NOAA National Oceanic and Atmospheric Administration 

NOPP National Oceanographic Partnership Program 

NOS National Ocean Service 

NSF National Science Foundation 

NTIA National Telecommunications and Information Administration 

NWLON National Water Level Observation Network 

OD Oceanographic Division 

OSTEP Ocean Systems Test and Evaluation Program 

PORTS® Physical Oceanographic Real-Time System 

QA/QC quality control/quality assurance 

RDI RD Instruments 

ROS Reliable Operating System 

RUDICS Router based Unrestricted Digital Interworking Connectivity Solution 

SBD Short Burst Data 

SBIR Small Business Innovation Research 

STIWG Satellite Telemetry Interagency Working Group 

USACE United States Army Corps of Engineers 

USGS United States Geological Survey