Current and emerging satellite technologies: implications for drifting buoy design

The Argos satellite system has been used to locate and telemeter data from drifting buoys since the late 1970s. With the advent of low cost GPS in the early 1990s, Argos-only drifters were joined by GPS/Argos buoys capable of higher accuracy positioning and many more positions per day than Argos alone. A number of innovative satellite systems, newly available or planned for the near future, have significant implications for drifting buoy design. The new technologies fall into two categories: positioning and telemetry. Currently civilian GPS receivers have a rated positional accuracy of 100 meters and a typical 2DRMS accuracy of 30-40 meters. Using currently available Wide Area Differential GPS (WADGPS) postprocessing techniques, ZDRMS accuracies of 2-3 meters have been achieved. The Wide Area Augmentation System (WAAS) being deployed by the US Federal Administration for precision navigation will soon provide differential correction data via geosynchronous satellites in real time. WAAS signals can be received by GPS receivers with no additional hardware or power requirements. Positional accuracies of 2 meters have been reported from WAAS system tests. WAAS should be available in the continental US by mid 2000 and WAAS-compatible systems are being developed in Europe and elsewhere. Within the next few years, a host of new satellite systems will join the existing services offering wireless data telemetry to the oceanographic community. The capabilities of these systems vary greatly, and it is important to select the "right size" of technology for drifting buoy use. Data capabilities, acquisition and operating costs, power requirements, geographic coverage, availability of suitable hardware, and reliability/viability of the service provider all must be considered.