Development of the RAPID MK III telemetry system – a report on the NOC tank-testing and shallow and deep-water field trials

This report describes the development of the RAPID Mk III telemetrysystem based on the combination of inductive mooringcommunications, an acoustic link to a nearby lander and timed release of data capsules to relay the data to shore via the Iridium satellite network. The lander is modified from the MYRTLE-X system to incorporate the acoustic modem link to the mooringand the mooringcommunications hub is built on prior experience from the Mk I and Mk II RAPID telemetrydevelopments that were ultimately aborted due to the risk to the mooringsof a permanent surface buoy. Development of the Mk III system began in 2013 and this report details field trials conducted as part of the development, with shallow water trials in Loch Etive, Scotland and deeper, longer duration trials offshore of Gran Canaria, Spain. The trials were successful with data from the mooredinstruments transferred as far as the data capsules. The Loch Etive trials demonstrated the manual release and onward data transmission of data from a data capsule. The automatic timed release has not been verified after some component failures during the Gran Canaria trials but the system has since been deployed on the RAPID array at 26N in the Atlantic. More information on that deployment will be available in the RRS Discovery DY039 cruise report when complete.