Operational Field Trials of GPS Equipped Sonobuoys

Peter Brown and Trevor Kirby-Smith

Abstract:	This paper describes a trial involving the NAVSYS TIDGETTM low-cost GPS sensor in fully-functioning sonobuoys in an operational environment. Sonobuoys are disposable air-launched buoys that are used in Anti-Submarine Warfare (ASW). Current techniques for localising the buoys once deployed are relatively inaccurate, time-consuming and involve aircraft manoeuvres in the vicinity of the buoy. Differential-GPS has been proposed as an alternative to the present localising techniques, however the sonobuoy environment leads to problems with a conventional GPS implementation. - Sonobuoys are disposable, and are therefore extremely cost sensitive. - Sonobuoys are stored for extended periods (many years), but must be operational immediately when deployed. - Large thermal transients occur on deployment from the aircraft into the sea. - The GPS antenna is subject to a high degree of masking due to its low elevation above the sea surface, aggravated by high sea-states and/or high winds. - Sonobuoys are battery powered and have limited available spare power for a GPS receiver. - Sonobuoys broadcast 1 Watt of RF power adjacent to the GPS antenna. This paper describes the GPS technology used for this application and its implementation in a fully-functional sonobuoy, and presents the results from a trials sortie flown in October 1995 using an RAF Nimrod Maritime Patrol aircraft and 9 sonobuoys in the water at the NATO AUTEC ASW range in the Bahamas. The results presented include a comparison between the TIDGET positional accuracies and the range instrumentation, and a summary of objectives met.
Published in:	Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996) September 17 - 20, 1996 Kansas City, MO
Pages:	1553 - 1561
Cite this article:	Brown, Peter, Kirby-Smith, Trevor, "Operational Field Trials of GPS Equipped Sonobuoys," Proceedings of the 9th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1996), Kansas City, MO, September 1996, pp. 1553-1561.
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