page_title: RAFOS float
section_title: Other results
hierarchical_section_title: RAFOS float / Measures and projects / Other results
caption_attribution_description: English: The trajectory of a float crossing the NAC (North Atlantic Current) (top) with the corresponding temperature (middle) and pressure records (bottom).
context_page_description: RAFOS floats are submersible devices used to map ocean currents well below the surface. They drift with these deep currents and listen for acoustic "pongs" emitted at designated times from multiple moored sound sources. By analyzing the time required for each pong to reach a float, researchers can pinpoint its position by triangulation. The floats are able to detect the pongs at ranges of hundreds of kilometers because they generally target a range of depths known as the SOFAR channel, which acts as a waveguide for sound. The name "RAFOS" derives from the earlier SOFAR floats, which emitted sounds that moored receivers picked up, allowing real-time underwater tracking. When the transmit and receive roles were reversed, so was the name: RAFOS is SOFAR spelled backward. Listening for sound requires far less energy than transmitting it, so RAFOS floats are cheaper and longer lasting than their predecessors, but they do not provide information in real-time: instead they store it on board, and upon completing their mission, drop a weight, rise to the surface, and transmit the data to shore by satellite.
context_section_description: Many results have been achieved thanks to these floats, on the global mapping of the ocean characteristics, or for example how floats systematically shoal (upwell) as they approach anticyclonic meanders and deepen (downwell) as they approach cyclonic meanders. On the left is a typical set of data from a RAFOS float. Today, such floats remain the best way to systematically probe the ocean's interior, since it is automatic and self-sufficient. In recent developments the floats have been able to measure different amounts of dissolved gases, and even to carry small experiments in situ.
caption: A float trajectory and the corresponding data.
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