Development and Testing of an A-Sized Rapidly Deployable Navigation and Communication GATEWAY Buoy

Abstract

A rapidly deployable, intelligent GATEWAY buoy system, capable of both air and sea deployment, has been developed to aid in the navigation and communication of Autonomous Underwater Vehicles (AUVs). The device is based around the A-sized (sonobuoy) standard and is deployable from aircraft, helicopters, ships and submarines using pressure and gravity launch tubes or charge-activated devices. The system consists of Florida Atlantic University (FAU) and Woods Hole Oceanographic Institute (WHOI) acoustic modems, both capable of providing Long Base Line (LBL) positioning, Global Positioning System (GPS) Wide Area Augmentation System (WAAS), and Radio Frequency (RF) communications. It utilizes a combined parachute and anchor, a low drag inflatable buoy, and an intelligent scope-adjusting mooring line spool. The design is based around a “fire-and-forget” methodology which, when the system is turned on and launched, requires no initial knowledge of the operating environment. The interoperable acoustic communication (ACOMMS) system can be operated at ranges up to 3000 meters and can achieve a true data rate of up to 860 bits-per-second using reliable spread-spectrum frequency modulation. The LBL positioning system operates sequentially and does not preclude acoustic communications. Switching between protocols (FAU or WHOI) is achieved through an automated process or is requested via RF commands. The mechanical system is modular and compact. The system is capable of operating in depths between 5 m and 200 m, in conditions up to sea state 3, and in currents up to 1.5 m/s. The mooring is versatile and able to hold in bottom types ranging from mud and sand to broken rock and reef.

High-Frequency Underwater Acoustic Propagation in a Port Modeled as a Three-Dimensional Duct Closed at One End Using the Method of Images

“…The function int() corresponds to the integer part of the result, F S = 75600 Hz is the sampling frequency, τ lmanb is the time of arrival of the echo produced by image S lmanb , and c is the sound speed in the channel. The source is an FAU Gateway Buoy [25] configured as a pinger, equipped with an ITC-3460 transducer and Global Positioning System with Wide Area Augmentation System (GPS-WAAS) of ±1 meter accuracy. The source transducer is suspended in the water column at a fixed depth of 1.5 meters below the sea-surface and transmits the chirp signal given in (28).…”