An ARGOS-reporting, A-size minibuoy that measures ocean ambient noise time histories for periods up to one month

Abstract

A new family of ARGOS-reporting, A-size minibuoys has been developed for the US Navy's Tactical Oceanographic Warfare Systems (TOWS) Program by METOCEAN Data Systems Limited of Dartmouth, Nova Scotia, Canada. These drifting buoys have a standard Navy classification-AN/WSQ-6 -and are certified for launch from P-3 maritime aircraft. In addition, the buoys have passed all the environmental and HERO testing required by the Navy. This paper discusses one variant of this family of buoys-the XAN-2 buoy which has a hydrophone positioned at 100 meters for ambient noise measurements as well as the standard meteorological sensors on all AN/WSQ-6 buoys-barometric pressure, air temperature and sea surface temperature. This paper traces the design evolution of these ambient noise measurement buoys from the initial design of the hydrophone suspension system to the current one in which operational lifetimes of 45 days or more are the norm. The initial design of the hydrophone compliance system was quite similar to that used by the Canadian Navy for their operational Sonobuoys and proved that ambient noise measurement could be made over the frequency spectrum from 5 Hz to 25 kHz. However, lifetimes of these Sonobuoys were limited to the order of a few days due to premature failure of the compliance system. The design improvements to the compliance system are discussed and various test results from open ocean deployments are discussed. Operational results from Naval Oceanographic Office (NAVO) deployments of these buoys will also be presented. Data are shown on the utility of estimating open ocean wind speeds based on the ambient noise measurements from these buoys.