RAFOS Floats in the North Atlantic; University of Rhode Island

RAFOS floats are neutrally buoyant isopycnal drifters, which are tracked
acoustically by ranging to as many as five sound sources that were moored at
the depth of the permanent sound channel south of the Gulf Stream along a line
between 73W and 51W. All sources transmit a precisely timed frequency
modulated, continuous wave (CW) signal every eight hours. The floats, which
are equipped with accurate timing, determine the times of arrival of the
signals. These are saved in the float's microprocessor memory along with
measurements of pressure and temperature. At the end of its mission, each
float releases ballast, returns to the surface and starts its radio telemetry.
The telemetered data are received by Systeme ARGOS, a French satellite--based
data collection and platform location system. Once the data have been
assembled in a computer, the trajectory of the float can be reconstructed from
the time series of acoustic travel times. Each RAFOS float data set contains
a time series of concurrent trajectory, temperature and pressure measurements.

The RAFOS system has been described in detail by Rossby et al. (1986). The
data processing has been discussed in a data report by Bower et al. (1986).
Floats were launched in the axis of the current, identified as the point at
which the 15 deg C isotherm crosses 450m. The actual launch site is
determined by a series of XBT's taken until the 15 deg C isotherm intersects
450m. The launch procedure is described in detail by Bower et al. (1986).