A GPS-tracked surface drifter with cellular telemetry capabilities

A location/data telemetry system has been configured for expendable surface drifters in coastal waters. The system is composed of a commercial microcontroller, a Global Positioning System (GPS) receiver, and a cellular phone with an integral modem. Drifter positions are periodically recorded by the microcontroller, which relays stored positions and ancillary data to an autonomous host computer on shore. Options include the capability to sample and store data from external sensors, remotely change mission parameters after deployment, such as sampling and reporting intervals, and a "sleep" mode to conserve power. Two surface platforms have been configured with the position/telemetry system. One is the spherical fiberglass hull of the World Ocean Circulation Experiment (WOCE) Surface Velocity Program, and the second is a modified Coastal Ocean Dynamics Experiment (CODE) surface drifter. Field tests indicate the surface drifters are capable of reliable communication in Florida coastal waters at least 30 km offshore under low sea state. The initiation of global cellular phone coverage within the next few years should provide an increased capability for tracking surface currents and the trajectories of drifting objects with this system.