New Antenna System Design Improves Reliability and Significantly Reduces Cost
By Edward Pritchard, AOML
Scientists and engineers from NOAA have successfully designed, built, and tested a new antenna system that dramatically increases data transmission reliability while drastically reducing operating costs. The new Iridium-based transmission system, developed by NOAA’s Atlantic Oceanographic & Meteorological Laboratory (AOML) & the Cooperative Institute for Marine & Atmospheric Studies (CIMAS), has no restrictions on data format or size, allowing data from various ocean and land-based observation platforms to be transmitted more securely and at a fraction of the cost of the older Inmarsat-C platform. Since its completion, AOML researchers have adopted the system on a number of expendable bathythermograph (XBTs) transects, as well as simultaneously tested and implemented it on other AOML observing systems.
Development of the system involved creating new transmission hardware and software. The system includes state of the art technologies combined with advanced algorithms to allow for the fast and stable transmission of digital data. Results from initial tests carried out in 2013 were used to optimize the system and to reduce or eliminate connection drops and data loss. It began its transition to operational capacity in 2015 and is currently being used on all cargo ships with XBT transects operated by AOML and the Scripps Oceanographic Institution.
Left: New Iridium antenna and housing. Right: Antenna installed aboard the CMA CGM Racine cargo vessel in Miami, FL, before the start of the January 2016 AX07 (Miami to Gibraltar) XBT transect.
Use of the new Iridium system has resulted in a 95% reduction of the average transmission cost per XBT profile, with an estimated savings to NOAA of more than $200,000 annually.
NOAA deploys approximately 12,000 XBTs per year as part of its contribution to the global XBT Network, a component of the Global Ocean Observing System. The network consists of approximately 50 fixed transects that are repeated several times every year.
XBTs are probes that measure temperature profiles to a depth of 800m. Data from the probes enable scientists to assess the transport of meridonial heat in the ocean, as well as the meridonial overturning circulation. The data also enable them to monitor key boundary, surface, and subsurface currents and account for amost 20 percent of all upper ocean temperature profiles obtained globally each year.
Since the early 2000s, XBT data have been processed and transmitted in real-time using the Inmarsat-C satellite network consisting of 12 geostationary telecommunications satellites. The data are then distributed into the Global Telecommunications System and used worldwide for climate research and weather and climate forecasts. However, the Inmarsat-C satellite network is costlier and does not allow for the transmission of different data types.
Although the new Iridium-based transmission system was originally developed for XBT observations, it is capable of transmitting additional forms and amounts of data. Its applicability has since been expanded to include ThermoSalinoGraph (TSG) and pCO2 systems, which measure underway temperature, salinity, and dissolved carbon dioxide in surface waters, respectively.
Other global oceanographic observational platforms such as Argo floats and drifting buoys also use the Iridium network for data transmission; however, these platforms use a protocol only suitable for smaller amounts of data. With the application of the new antenna system, which can transmit files of arbitrary size, these data can be transmitted at a lower cost and at a faster rate.
In addition to Iridium transmissions, the new system can be also be configured to transmit data over telephone landlines or computer networks, potentially decreasing many other operational costs. Plans for the system include increasing its use along XBT transects run by other XBT partner institutions, as well as its application to other types of real-time environmental data transmissions.