Deployment and Retrieval of Linear Hydrophone Arrays and Seismometers Under Arctic Ice.

• Main Authors: Gay,Shelton M , Jr, Nelligan,John J
• Other Authors: MAR ASSOCIATES INC ROCKVILLE MD
• Format: Text
• Language: English
• Published: 1976
• Subjects: Acoustic Detection and Detectors; Seismic Detection and Detectors; *DEPLOYMENT; *LINEAR ARRAYS; *UNDERICE; RECOVERY; INSTRUMENTATION; HYDROPHONES; TOWING CABLES; SEISMOMETERS; UNDERWATER EQUIPMENT; ARCTIC OCEAN; PACK ICE; WUNR294043; Arctic; Arctic Ocean
• Online Access: http://www.dtic.mil/docs/citations/ADA071404; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA071404

Methods are studied for placement and retrieval of instrumentation from beneath the Arctic ice pack. The instrumentation considered consists of long, linear hydrophone arrays (seismic arrays) and ocean-bottom seismometers and gravimeters. It is assumed that operations are conducted from an ice-locked ship having both complete oceanographic support and cable handling capabilities. An inverted two-legged mooring (by which the array is suspended beneath the ice in a horizontal position) is selected as the preferred configuration for the hydrophone array. Methods for installing the suspensions and array, and their subsequent recovery are developed. The effect of current, depth and array length are examined with respect to system forces, and performance trade-offs are identified. Deployment of the seismometer on the ocean bottom by means of a buoyant cable, constrained to float just above the ocean floor by weighted risers attached at intervals to the cable, is selected as the preferred configuration for the ocean-bottom seismometer. Cable is deployed slowly from the ship as it drifts with the ice, thus laying a transmission line above the ocean bottom. For recovery, the instrument is made buoyant by discharge of ballast and towed over the ocean floor to a position beneath the ship. Problems relative to these evolutions are identified and solutions suggested. (Author)