The Argos satellite system has been used in the past to transmit the data to shore and to compute the drifter position using the Doppler shift of the transmitter carrier frequency, yielding a geolocation accuracy that ranges from ~200 m to ~2 km (Lopez et al., 2014). A comprehensive set of diagnostic data that are crucial to monitoring the health of the drifter array, such as the battery voltage, the hull’s internal pressure, temperature, and humidity, are also formatted and appended to the data message.Īll drifters carry a satellite modem for data telemetry. The bench-accuracy of the SST measurements is ☐.05☌ after five-point bath calibration across the sensing range of the thermistor (–5☌ to 40☌).Īn LDL designed digital controller handles the duty cycle of the data collection (typically once per hour, but it can be changed underway using the two-way Iridium communication) and formats the data (SST and position) for satellite transmission.
The base of the thermistor enclosure that communicates with the inside of the drifter is thermally insulated from the inside of the buoy with a special resin to avoid biased sea surface temperature (SST) readings that may occur when the drifter’s hull overheats under the sun, especially at low latitudes. A thermistor potted with thermally conductive resin encapsulated into a stainless-steel enclosure is mounted in the bottom part of the surface buoy, 18 cm below the flotation line. The drogue is a cylindrical tube of rip-stop fabric nylon connected to the surface buoy with an impregnated steel wire-rope tether. The SVP drifter’s hull has a diameter of 35 cm and is made of acrylonitrile butadiene styrene (ABS).