R. K. Menoche R. J. Reid
Naval Undersea Warfare Ctr., Range Development Div., Newport, RI 02841
P. J. Stein
Scientific Solutions, Inc., Nashua, NH 03062
This presentation describes the design and testing of a novel baffled central up-link subsurface link (SSL) for the deep water portable tracking system (PTS). The central SSL is deployed at depths up to 350 m and collects the acoustic information from the bottom moored tracking transponders. These transponders can be deployed to depths down to 6000 m. Degradation of the up-link SSL performance is generally due to support ship radiated noise and surface generated ambient noise. These sources of interference can be suppressed with a downward looking receiver. This receiver must have a wide beamwidth (140 deg) and its response must fall off rapidly outside the beam to reject ambient noise. The device built consists of a hydrophone and projector mounted on the face of a steel signal conditioning plate (SCP). The plate is designed to have low vibration sensitivity. Behind the plate, and extending beyond the SCP edges, is a fiberglass air chamber. To prevent crushing, it is fed by an air-compensation bag. Extension of the air-backing beyond the SCP is important to ambient noise rejection. This soft surface helps to reject noise which diffracts around edge of the battle. The air-chamber design was chosen over material solutions because it was uncertain if, at the deeper depths, the latter could provide the pressure release surface required.