Sonar research conducted during the period 1 January - 31 March 1961

This is a report of activities supported under Contract NObsr-72521 for the period 1 January through 31 March 1961. It also contains mention of other reports, papers, and undertakings of the submarine geophysics group (listed under "Personnel") which are believed to be of interest to the Bureau of Ships. During this period no cruises have been supported directly under this contract. Eight members of the group under the leadership of Dr. Voorhis have participated in a cruise of CHAIN to the Romanche Trench. Their principal objective was to determine the sill depth which controls the exchange of deep, cold water ,between the western and eastern sides of the Atlantic Ocean. This sill was previously identified from hydrographic evidence to lie somewhat east of the Romanche Trench. A second objective was to continue the observations of temperature structure near the sea's surface with the thermistor chain. Another group, under Mr. Baxter's leadership, continued a sound transmission study in the Bermuda area in support of Project ARTEMIS. A third group, under Dr. Hays's direction, commenced a finely detailed bathymetric survey of an area of special interest to Project ARTEMIS. In all three of these studies we are making use of one or more experimental techniques in the use of sonobuoys, underwater acoustic navigation for submerged instruments, and sound coherence studies which are planned for use eventually in sound transmission and bottom reflection research under this contract.Bureau of Ships Under Contract NObsr-7252