Indian Journal of Geo Marine Sciences Vol. 47 (09), September 2018, pp. 1723-1726

Technical Note

SONO BOUYS

Raja Acharya

India Meteorological Department,Regional Meteorological Centre,Kolkata,Ministry of Earth Sciences 4, Duel Avenue,Alipore Kolkata-700027

[E.Mail: [email protected] ]

Received: 14 May 2018 Revised 20 July 2018

A bouy is an anchored floating device which serves as (http://navyaviation.tpub.com/14030/css/Sonobuoy a navigation mark, to show reefs or other hazards, or -Receivers-107.htm) for mooring. A Sono Bouy is a buoy equipped to Sono buoys are classified into three categories: detect underwater sounds, objects and transmit them active, passive and special purpose. by radio. It is a relatively small buoy (typically 13 cm Active sono buoy uses a transducer to radiate a or 5 in, in diameter and 91 cm or 3 ft long with sonar pulse that is reflected back from the target. The expendable sonar system that is dropped/ejected from time interval between the ping (sound pulse) and the aircraft or ships conducting anti-submarine warfare or echo return to the sono buoy is measured. Taking the underwater acoustic research. Doppler Effect on the pulse frequency into The sono buoy has 4 main components: a float, a consideration, this time-measurement data is used to radio transmitter, a saltwater battery, and a calculate both range and speed of the submarine hydrophone. Hydrophone is an underwater sensor relative to the sono buoy. The command activated that converts the pressure waves from underwater buoy is controlled by a UHF command signal from sounds into electrical voltages that get amplified and the aircraft. (http://navyaviation.tpub.com/14030/css/ send radio signals which are picked up by an antenna Special-Purpose- Sonobuoys-106.htm) and a radio receiver on the ship, then reviewed and The Directional Command Activated Sono buoy simultaneously recorded onto a digital audiotape. System (DICASS) sono buoy is an active acoustic Sono buoy can transmit for a maximum of 8 hrs sono buoy used by the Navy to detect submarines. before scuttling and sinking. The “command activated” part of the system allows Sono buoys are ejected from aircraft into the ocean DICASS buoys to receive radio transmissions in canisters. On water impact an inflatable surface instructing the buoy to change depth, activate sonar float with a radio transmitter remains on the surface transmissions. Active sonar pulses can be transmitted which communicates with the aircraft, while one or at four frequencies (6.5 kHz, 7.5 kHz, 8.5 kHz, and more hydrophone sensors and stabilizing equipment 9.5 kHz) and can operate for up to one hour at depths descend below the surface to a selected depth that is of up to 457 m (1,500 ft). The echo returns of the variable, depending on environmental conditions and active sonar signals provide range, bearing, and the search pattern. The buoy relays acoustic Doppler information on acoustic contacts. information from its hydrophone(s) via UHF/VHF Passive sonobuoys emit nothing into the water, but radio to operators on board the aircraft. Sonobuoys rather listen, waiting for sound waves (for instance, use a transducer and a radio transmitter to record and power plant, propeller and other noises) from ships or transmit underwater sounds. submarines, or other acoustic signals of interest such Spectrum analyzer is a high-speed signal processor as an aircraft's black box pinger, to reach the designed to extract acoustic target information from hydrophone. The sound is then transmitted via both active and passive sonobuoy data. The Spectrum UHF/VHF radio to a receiving ship or aircraft. Analyser determines frequency, amplitude, bearing, The Directional Frequency Analysis and Recording Doppler, range, and other characteristics for acoustic (DIFAR) sono buoy is a passive acoustics sono buoy targets. that is used by the Navy to detect underwater 1724 INDIAN J. MAR. SCI., VOL. 47, NO. 09, SEPTEMBER 2018

submarines. The DIFAR sono buoy detects acoustic ATAC/DLC—Air transportable communication energy from 5 to 2,400 Hz and can operate for up to (ATAC) and down-link communication (DLC) buoys, eight hours at depths of up to 1000 feet. These sono are intended for use as a means of communication buoys have also been used for research to track whale between an aircraft and a submarine, or between a populations and monitor underwater volcanic activity ship and a submarine. This information is analyzed by (https://dosits.org/galleries/technology-gallery/ locating- computers to interpret the sonobuoy information objects-by-listening-to-their-sounds/difar/) Special purpose sono buoys relay various types of Latest developments in Ocean Accoustics Monitoring oceanographic data to a ship, aircraft, or satellite. Hydrophone Arrays for detecting submarine Volacanoes There are three types of special-purpose sono buoys The NOAA (National Oceanic Atmospheric in use today. These sono buoys are not designed for use Administration) has been using the Hydrophone in submarine detection or localization. Arrays known as Sound Surveillance System(SOSUS) The bathythermobuoy (BT) relay bathy– for detecting underwater volcanic eruptions. Volcanic thermographic and/or salinity readings at various tremors from south of Japan have been successfully depths. detected and located using SOSUS arrays deployed SAR—The search and rescue (SAR) buoy is off the coasts of Oregon and Washington. designed to operate as a floating Radio frequency Detecting Microearthquakes (magnitude less than beacon. As such, it is used to assist in marking the 4.0) when detection not feasible with Ocean Bottom location of an aircraft crash site, a sunken ship, or Seismometer (Microearthquakes on the Galapagos survivors at sea. Spreading Centre and the Seismicity of Fast-

Block diagram of a DIFAR (Directional Frequency Analysis and Recording) Sono bouy (Ref: http://navyaviation.tpub.com/14030/css/ Special-Purpose-Sonobuoys-106.htm)

AN/SSQ-47B active pinger ranging sonar sono buoy.(Ref: https://en.wikipedia.org/wiki/Sonobuoy) ACHARYA: SONO BOUYS 1725

Deployment of Sono Boy from NOAA ship Oscar Dyson (Image Courtesy NOAA) (Ref: https://oczeanexplorer.noaa.gov/technology/tools/acoustics/sonobuoy.html)

Spreading Ridges by Kenneth C. Macdonald and objective of a Global Ocean Acoustic Observing John D. Mudie) Network, through which modest systems of acoustic receivers and sources deployed across ocean basins Future Challenges and Conclusion can make effective, sustained observations of a variety Sono bouys employ technology which are useful for of ocean processes and identify oceanic phenomena on military applications as well as search for underwater a global scale.(Dushaw .B et al A global ocean acoustic objects, tracking underwater volcanoes and sea observing network Proceedings of OceanObs’09: mammals. There is a need to to install numerous Sustained Ocean Observations and Information for hydrophone arrays around the global ocean with the Society, Vol. 2.) 1726 INDIAN J. MAR. SCI., VOL. 47, NO. 09, SEPTEMBER 2018

Acknowledgements 5 Ian Reid and Ken Macdonald, Microearthquake Study of the This technical note has been compiled using Mid-Atlantic Ridge near 37° N, using Sonobuoys, Nature ,246,(1973),88–90 internet information and other sources , basically to 6 Kenneth C. Macdonald and John D. Mudie, propagate the importance of SONO BOUYS. Microearthquakes on the Galapagos Spreading Centre and The views expressed in the article are solely my the Seismicity of Fast-Spreading Ridges ,Geophysical views and not of my organisation and my Journal International,36(1974),245-257. 7 https://dosits.org/galleries/technology-gallery/locating- employing organisation has no financial liability objects-by-listening-to-their-sounds/difar in the matter. 8 https://oceanexplorer.noaa.gov/technology/tools/acoustics/so nobuoy.html 9 http://navyaviation.tpub.com/14030/css/Special-Purpose- References Sonobuoys-106.htm 1 http://www.dosits.org/galleries/technology--Discovery of 10 Dushaw, B. & Co-Authors (2010). "A Global Ocean Acoustic sound in the sea Observing Network", Proceedings of OceanObs’09: Sustained 2 https://en.wikipedia.org/wiki/Sonobuoy Ocean Observations and Information for Society (Vol. 2), 3 https://en.wikipedia.org/wiki/Sonobuoy#/media/File:SSQ- Venice, Italy, 21-25 September 2009, Hall, J., Harrison, D.E. & 47B_sonobuoy.jpg Stammer, D., Eds., ESA PublicationWPP-306,doi:10.5270/ 4 http://cetus.ucsd.edu/technologies_Sonobuoy.html OceanObs09.cwp.25.